[PATCH v17 00/15] Introduce Data Access MONitor (DAMON)

[PATCH v17 00/15] Introduce Data Access MONitor (DAMON)

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

Changes from Previous Version
=============================

- Wordsmith/cleanup the documentations and the code
- user space tool: Cleanup and add an option for reuse histogram (patch 11)
- recording: Check disablement condition properly
- recording: Force minimal recording buffer size (1KB)

Introduction
============

DAMON is a data access monitoring framework subsystem for the Linux kernel.
The core mechanisms of DAMON called 'region based sampling' and 'adaptive
regions adjustment' (refer to 'mechanisms.rst' in the 11th patch of this
patchset for the detail) make it

 - accurate (The monitored information is useful for DRAM level memory
   management. It might not appropriate for Cache-level accuracy, though.),
 - light-weight (The monitoring overhead is low enough to be applied online
   while making no impact on the performance of the target workloads.), and
 - scalable (the upper-bound of the instrumentation overhead is controllable
   regardless of the size of target workloads.).

Using this framework, therefore, the kernel's core memory management mechanisms
such as reclamation and THP can be optimized for better memory management.  The
experimental memory management optimization works that incurring high
instrumentation overhead will be able to have another try.  In user space,
meanwhile, users who have some special workloads will be able to write
personalized tools or applications for deeper understanding and specialized
optimizations of their systems.

Evaluations
===========

We evaluated DAMON's overhead, monitoring quality and usefulness using 25
realistic workloads on my QEMU/KVM based virtual machine running a kernel that
v16 DAMON patchset is applied.

DAMON is lightweight. It increases system memory usage by only -0.25% and
consumes less than 1% CPU time in most case. It slows target workloads down by
only 0.94%.

DAMON is accurate and useful for memory management optimizations. An
experimental DAMON-based operation scheme for THP, 'ethp', removes 31.29% of
THP memory overheads while preserving 60.64% of THP speedup. Another
experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
reduces 87.95% of residential sets and 29.52% of system memory footprint while
incurring only 2.15% runtime overhead in the best case (parsec3/freqmine).

NOTE that the experimentail THP optimization and proactive reclamation are not
for production, just only for proof of concepts.

Please refer to the official document[1] or "Documentation/admin-guide/mm: Add
a document for DAMON" patch in this patchset for detailed evaluation setup and
results.

[1] https://damonitor.github.io/doc/html/latest-damon/admin-guide/mm/damon/eval.html

More Information
================

We prepared a showcase web site[1] that you can get more information.  There
are

- the official documentations[2],
- the heatmap format dynamic access pattern of various realistic workloads for
  heap area[3], mmap()-ed area[4], and stack[5] area,
- the dynamic working set size distribution[6] and chronological working set
  size changes[7], and
- the latest performance test results[8].

[1] https://damonitor.github.io/_index
[2] https://damonitor.github.io/doc/html/latest-damon
[3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.0.png.html
[4] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
[5] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.2.png.html
[6] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
[7] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.png.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html

Baseline and Complete Git Trees
===============================

The patches are based on the v5.7.  You can also clone the complete git
tree:

    $ git clone git://github.com/sjp38/linux -b damon/patches/v17

The web is also available:
https://github.com/sjp38/linux/releases/tag/damon/patches/v17

There are a couple of trees for entire DAMON patchset series.  It includes
future features.  The first one[1] contains the changes for latest release,
while the other one[2] contains the changes for next release.

[1] https://github.com/sjp38/linux/tree/damon/master
[2] https://github.com/sjp38/linux/tree/damon/next

Sequence Of Patches
===================

The 1st patch exports 'lookup_page_ext()' to GPL modules so that it can be used
by DAMON even though it is built as a loadable module.

Next four patches implement the target address space independent core logics of
DAMON and it's programming interface.  The 2nd patch introduces DAMON module,
it's data structures, and data structure related common functions.  Following
three patches (3rd to 5th) implements the core mechanisms of DAMON, namely
regions based sampling (patch 3), adaptive regions adjustment (patch 4), and
dynamic memory mapping chage adoption (patch 5).

The following one (patch 6) implements the virtual memory address space
specific functions.

Following four patches are for more user friendly interfaces.  The 7th patch
implements recording of access patterns in DAMON.  Each of next two patches
(8th and 9th) respectively adds a tracepoint for other tracepoints supporting
tracers such as perf, and a debugfs interface for privileged people and/or
programs in user space.

Three patches for high level users of DAMON follows.  To provide a minimal
reference to the debugfs interface and for high level use/tests of the DAMON,
the next patch (10th) implements an user space tool.  The 11th patch adds one
more option to the tool for reuse histogram plot.  The 12nd patch adds a
document for administrators of DAMON.

Next two patches are for tests.  The 13th patch provides unit tests (based on
the kunit) while the 14th patch adds user space tests (based on the kselftest).

Finally, the last patch (15th) updates the MAINTAINERS file.

Patch History
=============

This version of patchset merges first, second, and sixth patches in the CDAMON
patchset[1] for better readability.  As the changes are not subtle,
'Reviewed-by's I previously received on the changes affected patches are also
dropped.

[1] https://lore.kernel.org/linux-mm/20200609141941.19184-1-sjpark@amazon.com/

Changes from v16
(https://lore.kernel.org/linux-mm/20200615161927.12637-1-sjpark@amazon.com/)
 - Wordsmith/cleanup the documentations and the code
 - user space tool: Simplify the code and add wss option for reuse histogram
 - recording: Check disablement condition properly
 - recording: Force minimal recording buffer size (1KB)

Changes from v15
(https://lore.kernel.org/linux-mm/20200608114047.26589-1-sjpark@amazon.com/)
 - Refine commit messages (David Hildenbrand)
 - Optimizes three vma regions search (Varad Gautam)
 - Support static granularity monitoring (Shakeel Butt)
 - Cleanup code and re-organize the sequence of patches

Changes from v14
(https://lore.kernel.org/linux-mm/20200602130125.20467-1-sjpark@amazon.com/)
 - Directly pass region and task to tracepoint (Steven Rostedt)
 - Refine comments for better read
 - Add more 'Reviewed-by's (Leonard Foerster, Brendan Higgins)

Changes from v13
(https://lore.kernel.org/linux-mm/20200525091512.30391-1-sjpark@amazon.com/)
 - Fix a typo (Leonard Foerster)
 - Fix wring condition of three sub ranges split (Leonard Foerster)
 - Rebase on v5.7

Changes from v12
(https://lore.kernel.org/linux-mm/20200518100018.2293-1-sjpark@amazon.com/)
 - Avoid races between debugfs readers and writers
 - Add kernel-doc comments in damon.h

Changes from v11
(https://lore.kernel.org/linux-mm/20200511123302.12520-1-sjpark@amazon.com/)
 - Rewrite the document (Stefan Nuernberger)
 - Make 'damon_for_each_*' argument order consistent (Leonard Foerster)
 - Fix wrong comment in 'kdamond_merge_regions()' (Leonard Foerster)

Changes from v10
(https://lore.kernel.org/linux-mm/20200505110815.10532-1-sjpark@amazon.com/)
 - Reduce aggressive split overhead by doing it only if required

Changes from v9
(https://lore.kernel.org/linux-mm/20200427120442.24179-1-sjpark@amazon.com/)
 - Split each region into 4 subregions if possible (Jonathan Cameraon)
 - Update kunit test for the split code change

Please refer to the v9 patchset to get older history.

SeongJae Park (15):
  mm/page_ext: Export lookup_page_ext() to GPL modules
  mm: Introduce Data Access MONitor (DAMON)
  mm/damon: Implement region based sampling
  mm/damon: Adaptively adjust regions
  mm/damon: Track dynamic monitoring target regions update
  mm/damon: Implement callbacks for the virtual memory address spaces
  mm/damon: Implement access pattern recording
  mm/damon: Add a tracepoint
  mm/damon: Implement a debugfs interface
  tools: Introduce a minimal user-space tool for DAMON
  tools/damon/wss: Implement '--thres' option
  Documentation/admin-guide/mm: Add a document for DAMON
  mm/damon: Add kunit tests
  mm/damon: Add user space selftests
  MAINTAINERS: Update for DAMON

 Documentation/admin-guide/mm/damon/api.rst    |   20 +
 .../admin-guide/mm/damon/damon_heatmap.png    |  Bin 0 -> 8366 bytes
 .../admin-guide/mm/damon/damon_wss_change.png |  Bin 0 -> 7211 bytes
 .../admin-guide/mm/damon/damon_wss_dist.png   |  Bin 0 -> 6173 bytes
 Documentation/admin-guide/mm/damon/eval.rst   |  222 +++
 Documentation/admin-guide/mm/damon/faq.rst    |   59 +
 .../admin-guide/mm/damon/freqmine_heatmap.png |  Bin 0 -> 9999 bytes
 .../admin-guide/mm/damon/freqmine_wss_sz.png  |  Bin 0 -> 5589 bytes
 .../mm/damon/freqmine_wss_time.png            |  Bin 0 -> 6550 bytes
 Documentation/admin-guide/mm/damon/guide.rst  |  194 ++
 Documentation/admin-guide/mm/damon/index.rst  |   35 +
 .../admin-guide/mm/damon/mechanisms.rst       |  159 ++
 Documentation/admin-guide/mm/damon/plans.rst  |   29 +
 Documentation/admin-guide/mm/damon/start.rst  |  117 ++
 .../mm/damon/streamcluster_heatmap.png        |  Bin 0 -> 42210 bytes
 .../mm/damon/streamcluster_wss_sz.png         |  Bin 0 -> 6327 bytes
 .../mm/damon/streamcluster_wss_time.png       |  Bin 0 -> 8830 bytes
 Documentation/admin-guide/mm/damon/usage.rst  |  296 +++
 Documentation/admin-guide/mm/index.rst        |    1 +
 MAINTAINERS                                   |   12 +
 include/linux/damon.h                         |  175 ++
 include/trace/events/damon.h                  |   43 +
 mm/Kconfig                                    |   23 +
 mm/Makefile                                   |    1 +
 mm/damon-test.h                               |  661 +++++++
 mm/damon.c                                    | 1632 +++++++++++++++++
 mm/page_ext.c                                 |    1 +
 tools/damon/.gitignore                        |    1 +
 tools/damon/_damon.py                         |  129 ++
 tools/damon/_dist.py                          |   36 +
 tools/damon/_recfile.py                       |   23 +
 tools/damon/bin2txt.py                        |   67 +
 tools/damon/damo                              |   37 +
 tools/damon/heats.py                          |  362 ++++
 tools/damon/nr_regions.py                     |   91 +
 tools/damon/record.py                         |  106 ++
 tools/damon/report.py                         |   45 +
 tools/damon/wss.py                            |   99 +
 tools/testing/selftests/damon/Makefile        |    7 +
 .../selftests/damon/_chk_dependency.sh        |   28 +
 tools/testing/selftests/damon/_chk_record.py  |  108 ++
 .../testing/selftests/damon/debugfs_attrs.sh  |  139 ++
 .../testing/selftests/damon/debugfs_record.sh |   50 +
 43 files changed, 5008 insertions(+)
 create mode 100644 Documentation/admin-guide/mm/damon/api.rst
 create mode 100644 Documentation/admin-guide/mm/damon/damon_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_change.png
 create mode 100644 Documentation/admin-guide/mm/damon/damon_wss_dist.png
 create mode 100644 Documentation/admin-guide/mm/damon/eval.rst
 create mode 100644 Documentation/admin-guide/mm/damon/faq.rst
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/freqmine_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/guide.rst
 create mode 100644 Documentation/admin-guide/mm/damon/index.rst
 create mode 100644 Documentation/admin-guide/mm/damon/mechanisms.rst
 create mode 100644 Documentation/admin-guide/mm/damon/plans.rst
 create mode 100644 Documentation/admin-guide/mm/damon/start.rst
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_heatmap.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_sz.png
 create mode 100644 Documentation/admin-guide/mm/damon/streamcluster_wss_time.png
 create mode 100644 Documentation/admin-guide/mm/damon/usage.rst
 create mode 100644 include/linux/damon.h
 create mode 100644 include/trace/events/damon.h
 create mode 100644 mm/damon-test.h
 create mode 100644 mm/damon.c
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_damon.py
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
 create mode 100644 tools/testing/selftests/damon/_chk_record.py
 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

-- 
2.17.1

[PATCH v17 01/15] mm/page_ext: Export lookup_page_ext() to GPL modules

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit exports 'lookup_page_ext()' to GPL modules.  It will be used
by DAMON in following commit for the implementation of the region based
sampling.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
Reviewed-by: Varad Gautam <vrd@amazon.de>
---
 mm/page_ext.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/mm/page_ext.c b/mm/page_ext.c
index a3616f7a0e9e..9d802d01fcb5 100644
--- a/mm/page_ext.c
+++ b/mm/page_ext.c
@@ -131,6 +131,7 @@ struct page_ext *lookup_page_ext(const struct page *page)
 					MAX_ORDER_NR_PAGES);
 	return get_entry(base, index);
 }
+EXPORT_SYMBOL_GPL(lookup_page_ext);
 
 static int __init alloc_node_page_ext(int nid)
 {
-- 
2.17.1

[PATCH v17 02/15] mm: Introduce Data Access MONitor (DAMON)

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

DAMON is a data access monitoring framework subsystem for the Linux
kernel.  The core mechanisms of DAMON make it

 - accurate (the monitoring output is useful enough for DRAM level
   memory management; It might not appropriate for CPU Cache levels,
   though),
 - light-weight (the monitoring overhead is low enough to be applied
   online), and
 - scalable (the upper-bound of the overhead is in constant range
   regardless of the size of target workloads).

Using this framework, therefore, the kernel's memory management
mechanisms can make advanced decisions.  Experimental memory management
optimization works that incurring high data accesses monitoring overhead
could implemented again.  In user space, meanwhile, users who have some
special workloads can write personalized applications for better
understanding and optimizations of their workloads and systems.

This commit is implementing only the stub for the module load/unload,
basic data structures, and simple manipulation functions of the
structures to keep the size of commit small.  The core mechanisms of
DAMON will be implemented one by one by following commits.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
Reviewed-by: Varad Gautam <vrd@amazon.de>
---
 include/linux/damon.h |  63 ++++++++++++++
 mm/Kconfig            |  12 +++
 mm/Makefile           |   1 +
 mm/damon.c            | 188 ++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 264 insertions(+)
 create mode 100644 include/linux/damon.h
 create mode 100644 mm/damon.c

diff --git a/include/linux/damon.h b/include/linux/damon.h
new file mode 100644
index 000000000000..c8f8c1c41a45
--- /dev/null
+++ b/include/linux/damon.h
@@ -0,0 +1,63 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * DAMON api
+ *
+ * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#ifndef _DAMON_H_
+#define _DAMON_H_
+
+#include <linux/random.h>
+#include <linux/types.h>
+
+/**
+ * struct damon_addr_range - Represents an address region of [@start, @end).
+ * @start:	Start address of the region (inclusive).
+ * @end:	End address of the region (exclusive).
+ */
+struct damon_addr_range {
+	unsigned long start;
+	unsigned long end;
+};
+
+/**
+ * struct damon_region - Represents a monitoring target region.
+ * @ar:			The address range of the region.
+ * @sampling_addr:	Address of the sample for the next access check.
+ * @nr_accesses:	Access frequency of this region.
+ * @list:		List head for siblings.
+ */
+struct damon_region {
+	struct damon_addr_range ar;
+	unsigned long sampling_addr;
+	unsigned int nr_accesses;
+	struct list_head list;
+};
+
+/**
+ * struct damon_task - Represents a monitoring target task.
+ * @pid:		Process id of the task.
+ * @regions_list:	Head of the monitoring target regions of this task.
+ * @list:		List head for siblings.
+ *
+ * If the monitoring target address space is task independent (e.g., physical
+ * memory address space monitoring), @pid should be '-1'.
+ */
+struct damon_task {
+	int pid;
+	struct list_head regions_list;
+	struct list_head list;
+};
+
+/**
+ * struct damon_ctx - Represents a context for each monitoring.
+ * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
+ */
+struct damon_ctx {
+	struct list_head tasks_list;	/* 'damon_task' objects */
+};
+
+#endif
diff --git a/mm/Kconfig b/mm/Kconfig
index c1acc34c1c35..464e9594dcec 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -867,4 +867,16 @@ config ARCH_HAS_HUGEPD
 config MAPPING_DIRTY_HELPERS
         bool
 
+config DAMON
+	tristate "Data Access Monitor"
+	depends on MMU
+	help
+	  This feature allows to monitor access frequency of each memory
+	  region. The information can be useful for performance-centric DRAM
+	  level memory management.
+
+	  See https://damonitor.github.io/doc/html/latest-damon/index.html for
+	  more information.
+	  If unsure, say N.
+
 endmenu
diff --git a/mm/Makefile b/mm/Makefile
index fccd3756b25f..230e545b6e07 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -112,3 +112,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o
 obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
 obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
 obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
+obj-$(CONFIG_DAMON) += damon.o
diff --git a/mm/damon.c b/mm/damon.c
new file mode 100644
index 000000000000..5ab13b1c15cf
--- /dev/null
+++ b/mm/damon.c
@@ -0,0 +1,188 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Data Access Monitor
+ *
+ * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ *
+ * This file is constructed in below parts.
+ *
+ * - Functions and macros for DAMON data structures
+ * - Functions for the module loading/unloading
+ *
+ * The core parts are not implemented yet.
+ */
+
+#define pr_fmt(fmt) "damon: " fmt
+
+#include <linux/damon.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/*
+ * Functions and macros for DAMON data structures
+ */
+
+#define damon_get_task_struct(t) \
+	(get_pid_task(find_vpid(t->pid), PIDTYPE_PID))
+
+#define damon_next_region(r) \
+	(container_of(r->list.next, struct damon_region, list))
+
+#define damon_prev_region(r) \
+	(container_of(r->list.prev, struct damon_region, list))
+
+#define damon_for_each_region(r, t) \
+	list_for_each_entry(r, &t->regions_list, list)
+
+#define damon_for_each_region_safe(r, next, t) \
+	list_for_each_entry_safe(r, next, &t->regions_list, list)
+
+#define damon_for_each_task(t, ctx) \
+	list_for_each_entry(t, &(ctx)->tasks_list, list)
+
+#define damon_for_each_task_safe(t, next, ctx) \
+	list_for_each_entry_safe(t, next, &(ctx)->tasks_list, list)
+
+/* Get a random number in [l, r) */
+#define damon_rand(l, r) (l + prandom_u32() % (r - l))
+
+/*
+ * Construct a damon_region struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+static struct damon_region *damon_new_region(unsigned long start,
+					     unsigned long end)
+{
+	struct damon_region *region;
+
+	region = kmalloc(sizeof(*region), GFP_KERNEL);
+	if (!region)
+		return NULL;
+
+	region->ar.start = start;
+	region->ar.end = end;
+	region->nr_accesses = 0;
+	INIT_LIST_HEAD(&region->list);
+
+	return region;
+}
+
+/*
+ * Add a region between two other regions
+ */
+static inline void damon_insert_region(struct damon_region *r,
+		struct damon_region *prev, struct damon_region *next)
+{
+	__list_add(&r->list, &prev->list, &next->list);
+}
+
+static void damon_add_region(struct damon_region *r, struct damon_task *t)
+{
+	list_add_tail(&r->list, &t->regions_list);
+}
+
+static void damon_del_region(struct damon_region *r)
+{
+	list_del(&r->list);
+}
+
+static void damon_free_region(struct damon_region *r)
+{
+	kfree(r);
+}
+
+static void damon_destroy_region(struct damon_region *r)
+{
+	damon_del_region(r);
+	damon_free_region(r);
+}
+
+/*
+ * Construct a damon_task struct
+ *
+ * Returns the pointer to the new struct if success, or NULL otherwise
+ */
+static struct damon_task *damon_new_task(int pid)
+{
+	struct damon_task *t;
+
+	t = kmalloc(sizeof(*t), GFP_KERNEL);
+	if (!t)
+		return NULL;
+
+	t->pid = pid;
+	INIT_LIST_HEAD(&t->regions_list);
+
+	return t;
+}
+
+static void damon_add_task(struct damon_ctx *ctx, struct damon_task *t)
+{
+	list_add_tail(&t->list, &ctx->tasks_list);
+}
+
+static void damon_del_task(struct damon_task *t)
+{
+	list_del(&t->list);
+}
+
+static void damon_free_task(struct damon_task *t)
+{
+	struct damon_region *r, *next;
+
+	damon_for_each_region_safe(r, next, t)
+		damon_free_region(r);
+	kfree(t);
+}
+
+static void damon_destroy_task(struct damon_task *t)
+{
+	damon_del_task(t);
+	damon_free_task(t);
+}
+
+static unsigned int nr_damon_tasks(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	unsigned int nr_tasks = 0;
+
+	damon_for_each_task(t, ctx)
+		nr_tasks++;
+
+	return nr_tasks;
+}
+
+static unsigned int nr_damon_regions(struct damon_task *t)
+{
+	struct damon_region *r;
+	unsigned int nr_regions = 0;
+
+	damon_for_each_region(r, t)
+		nr_regions++;
+
+	return nr_regions;
+}
+
+/*
+ * Functions for the module loading/unloading
+ */
+
+static int __init damon_init(void)
+{
+	return 0;
+}
+
+static void __exit damon_exit(void)
+{
+}
+
+module_init(damon_init);
+module_exit(damon_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("SeongJae Park <sjpark@amazon.de>");
+MODULE_DESCRIPTION("DAMON: Data Access MONitor");
-- 
2.17.1

[PATCH v17 03/15] mm/damon: Implement region based sampling

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements DAMON's target address space independent high
level logics for basic access check and region based sampling.  This
doesn't work alone, but needs the target address space specific low
level pritimives implementation for the monitoring target address ranges
construction and the access check, though.  A reference implementation
of those will be provided by a later commit.  Nevertheless, users can
implement and use their own versions for their specific use cases.

Basic Access Check
==================

The output of DAMON says what pages are how frequently accessed for a
given duration.  The resolution of the access frequency is controlled by
setting ``sampling interval`` and ``aggregation interval``.  In detail,
DAMON checks access to each page per ``sampling interval`` and
aggregates the results.  In other words, counts the number of the
accesses to each page.  After each ``aggregation interval`` passes,
DAMON calls callback functions that previously registered by users so
that users can read the aggregated results and then clears the results.
This can be described in below simple pseudo-code::

    while monitoring_on:
        for page in monitoring_target:
            if accessed(page):
                nr_accesses[page] += 1
        if time() % aggregation_interval == 0:
            for callback in user_registered_callbacks:
                callback(monitoring_target, nr_accesses)
            for page in monitoring_target:
                nr_accesses[page] = 0
        sleep(sampling interval)

The monitoring overhead of this mechanism will arbitrarily increase as
the size of the target workload grows.

Region Based Sampling
=====================

To avoid the unbounded increase of the overhead, DAMON groups adjacent
pages that assumed to have the same access frequencies into a region.
As long as the assumption (pages in a region have the same access
frequencies) is kept, only one page in the region is required to be
checked.  Thus, for each ``sampling interval``, DAMON randomly picks one
page in each region, waits for one ``sampling interval``, checks whether
the page is accessed meanwhile, and increases the access frequency of
the region if so.  Therefore, the monitoring overhead is controllable by
setting the number of regions.  DAMON allows users to set the minimum
and the maximum number of regions for the trade-off.

This scheme, however, cannot preserve the quality of the output if the
assumption is not guaranteed.  Next commit will address this problem.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  80 ++++++++++++-
 mm/damon.c            | 258 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 335 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index c8f8c1c41a45..7adc7b6b3507 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -11,6 +11,8 @@
 #define _DAMON_H_
 
 #include <linux/random.h>
+#include <linux/mutex.h>
+#include <linux/time64.h>
 #include <linux/types.h>
 
 /**
@@ -53,11 +55,87 @@ struct damon_task {
 };
 
 /**
- * struct damon_ctx - Represents a context for each monitoring.
+ * struct damon_ctx - Represents a context for each monitoring.  This is the
+ * main interface that allows users to set the attributes and get the results
+ * of the monitoring.
+ *
+ * @sample_interval:		The time between access samplings.
+ * @aggr_interval:		The time between monitor results aggregations.
+ * @nr_regions:			The number of monitoring regions.
+ *
+ * For each @sample_interval, DAMON checks whether each region is accessed or
+ * not.  It aggregates and keeps the access information (number of accesses to
+ * each region) for @aggr_interval time.  All time intervals are in
+ * micro-seconds.
+ *
+ * @kdamond:		Kernel thread who does the monitoring.
+ * @kdamond_stop:	Notifies whether kdamond should stop.
+ * @kdamond_lock:	Mutex for the synchronizations with @kdamond.
+ *
+ * For each monitoring request (damon_start()), a kernel thread for the
+ * monitoring is created.  The pointer to the thread is stored in @kdamond.
+ *
+ * The monitoring thread sets @kdamond to NULL when it terminates.  Therefore,
+ * users can know whether the monitoring is ongoing or terminated by reading
+ * @kdamond.  Also, users can ask @kdamond to be terminated by writing non-zero
+ * to @kdamond_stop.  Reads and writes to @kdamond and @kdamond_stop from
+ * outside of the monitoring thread must be protected by @kdamond_lock.
+ *
+ * Note that the monitoring thread protects only @kdamond and @kdamond_stop via
+ * @kdamond_lock.  Accesses to other fields must be protected by themselves.
+ *
  * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
+ *
+ * @init_target_regions:	Constructs initial monitoring target regions.
+ * @prepare_access_checks:	Prepares next access check of target regions.
+ * @check_accesses:		Checks the access of target regions.
+ * @sample_cb:			Called for each sampling interval.
+ * @aggregate_cb:		Called for each aggregation interval.
+ *
+ * DAMON can be extended for various address spaces by users.  For this, users
+ * can register the target address space dependent low level functions for
+ * their usecases via the callback pointers of the context.  The monitoring
+ * thread calls @init_target_regions before starting the monitoring, and
+ * @prepare_access_checks and @check_accesses for each @sample_interval.
+ *
+ * @init_target_regions should construct proper monitoring target regions and
+ * link those to the DAMON context struct.
+ * @prepare_access_checks should manipulate the monitoring regions to be
+ * prepare for the next access check.
+ * @check_accesses should check the accesses to each region that made after the
+ * last preparation and update the `->nr_accesses` of each region.
+ *
+ * @sample_cb and @aggregate_cb are called from @kdamond for each of the
+ * sampling intervals and aggregation intervals, respectively.  Therefore,
+ * users can safely access to the monitoring results via @tasks_list without
+ * additional protection of @kdamond_lock.  For the reason, users are
+ * recommended to use these callback for the accesses to the results.
  */
 struct damon_ctx {
+	unsigned long sample_interval;
+	unsigned long aggr_interval;
+	unsigned long nr_regions;
+
+	struct timespec64 last_aggregation;
+
+	struct task_struct *kdamond;
+	bool kdamond_stop;
+	struct mutex kdamond_lock;
+
 	struct list_head tasks_list;	/* 'damon_task' objects */
+
+	/* callbacks */
+	void (*init_target_regions)(struct damon_ctx *context);
+	void (*prepare_access_checks)(struct damon_ctx *context);
+	unsigned int (*check_accesses)(struct damon_ctx *context);
+	void (*sample_cb)(struct damon_ctx *context);
+	void (*aggregate_cb)(struct damon_ctx *context);
 };
 
+int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_start(struct damon_ctx *ctx);
+int damon_stop(struct damon_ctx *ctx);
+
 #endif
diff --git a/mm/damon.c b/mm/damon.c
index 5ab13b1c15cf..5d0b3ab684b3 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -9,18 +9,27 @@
  * This file is constructed in below parts.
  *
  * - Functions and macros for DAMON data structures
+ * - Functions for DAMON core logics and features
+ * - Functions for the DAMON programming interface
  * - Functions for the module loading/unloading
- *
- * The core parts are not implemented yet.
  */
 
 #define pr_fmt(fmt) "damon: " fmt
 
 #include <linux/damon.h>
+#include <linux/delay.h>
+#include <linux/kthread.h>
 #include <linux/mm.h>
 #include <linux/module.h>
+#include <linux/page_idle.h>
+#include <linux/random.h>
+#include <linux/sched/mm.h>
+#include <linux/sched/task.h>
 #include <linux/slab.h>
 
+/* Minimal region size.  Every damon_region is aligned by this. */
+#define MIN_REGION PAGE_SIZE
+
 /*
  * Functions and macros for DAMON data structures
  */
@@ -167,6 +176,251 @@ static unsigned int nr_damon_regions(struct damon_task *t)
 	return nr_regions;
 }
 
+/*
+ * Functions for DAMON core logics and features
+ */
+
+/*
+ * damon_check_reset_time_interval() - Check if a time interval is elapsed.
+ * @baseline:	the time to check whether the interval has elapsed since
+ * @interval:	the time interval (microseconds)
+ *
+ * See whether the given time interval has passed since the given baseline
+ * time.  If so, it also updates the baseline to current time for next check.
+ *
+ * Return:	true if the time interval has passed, or false otherwise.
+ */
+static bool damon_check_reset_time_interval(struct timespec64 *baseline,
+		unsigned long interval)
+{
+	struct timespec64 now;
+
+	ktime_get_coarse_ts64(&now);
+	if ((timespec64_to_ns(&now) - timespec64_to_ns(baseline)) <
+			interval * 1000)
+		return false;
+	*baseline = now;
+	return true;
+}
+
+/*
+ * Check whether it is time to flush the aggregated information
+ */
+static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_aggregation,
+			ctx->aggr_interval);
+}
+
+/*
+ * Reset the aggregated monitoring results
+ */
+static void kdamond_reset_aggregated(struct damon_ctx *c)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	damon_for_each_task(t, c) {
+		damon_for_each_region(r, t)
+			r->nr_accesses = 0;
+	}
+}
+
+/*
+ * Check whether current monitoring should be stopped
+ *
+ * The monitoring is stopped when either the user requested to stop, or all
+ * monitoring target tasks are dead.
+ *
+ * Returns true if need to stop current monitoring.
+ */
+static bool kdamond_need_stop(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct task_struct *task;
+	bool stop;
+
+	mutex_lock(&ctx->kdamond_lock);
+	stop = ctx->kdamond_stop;
+	mutex_unlock(&ctx->kdamond_lock);
+	if (stop)
+		return true;
+
+	damon_for_each_task(t, ctx) {
+		/* -1 is reserved for non-process bounded monitoring */
+		if (t->pid == -1)
+			return false;
+
+		task = damon_get_task_struct(t);
+		if (task) {
+			put_task_struct(task);
+			return false;
+		}
+	}
+
+	return true;
+}
+
+/*
+ * The monitoring daemon that runs as a kernel thread
+ */
+static int kdamond_fn(void *data)
+{
+	struct damon_ctx *ctx = (struct damon_ctx *)data;
+	struct damon_task *t;
+	struct damon_region *r, *next;
+
+	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
+	if (ctx->init_target_regions)
+		ctx->init_target_regions(ctx);
+	while (!kdamond_need_stop(ctx)) {
+		if (ctx->prepare_access_checks)
+			ctx->prepare_access_checks(ctx);
+		if (ctx->sample_cb)
+			ctx->sample_cb(ctx);
+
+		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
+
+		if (ctx->check_accesses)
+			ctx->check_accesses(ctx);
+
+		if (kdamond_aggregate_interval_passed(ctx)) {
+			if (ctx->aggregate_cb)
+				ctx->aggregate_cb(ctx);
+			kdamond_reset_aggregated(ctx);
+		}
+
+	}
+	damon_for_each_task(t, ctx) {
+		damon_for_each_region_safe(r, next, t)
+			damon_destroy_region(r);
+	}
+	pr_debug("kdamond (%d) finishes\n", ctx->kdamond->pid);
+	mutex_lock(&ctx->kdamond_lock);
+	ctx->kdamond = NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+
+	do_exit(0);
+}
+
+/*
+ * Functions for the DAMON programming interface
+ */
+
+static bool damon_kdamond_running(struct damon_ctx *ctx)
+{
+	bool running;
+
+	mutex_lock(&ctx->kdamond_lock);
+	running = ctx->kdamond != NULL;
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return running;
+}
+
+/**
+ * damon_start() - Starts monitoring with given context.
+ * @ctx:	monitoring context
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_start(struct damon_ctx *ctx)
+{
+	int err = -EBUSY;
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (!ctx->kdamond) {
+		err = 0;
+		ctx->kdamond_stop = false;
+		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond");
+		if (IS_ERR(ctx->kdamond))
+			err = PTR_ERR(ctx->kdamond);
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return err;
+}
+
+/**
+ * damon_stop() - Stops monitoring of given context.
+ * @ctx:	monitoring context
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_stop(struct damon_ctx *ctx)
+{
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ctx->kdamond_stop = true;
+		mutex_unlock(&ctx->kdamond_lock);
+		while (damon_kdamond_running(ctx))
+			usleep_range(ctx->sample_interval,
+					ctx->sample_interval * 2);
+		return 0;
+	}
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return -EPERM;
+}
+
+/**
+ * damon_set_pids() - Set monitoring target processes.
+ * @ctx:	monitoring context
+ * @pids:	array of target processes pids
+ * @nr_pids:	number of entries in @pids
+ *
+ * This function should not be called while the kdamond is running.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
+{
+	ssize_t i;
+	struct damon_task *t, *next;
+
+	damon_for_each_task_safe(t, next, ctx)
+		damon_destroy_task(t);
+
+	for (i = 0; i < nr_pids; i++) {
+		t = damon_new_task(pids[i]);
+		if (!t) {
+			pr_err("Failed to alloc damon_task\n");
+			return -ENOMEM;
+		}
+		damon_add_task(ctx, t);
+	}
+
+	return 0;
+}
+
+/**
+ * damon_set_attrs() - Set attributes for the monitoring.
+ * @ctx:		monitoring context
+ * @sample_int:		time interval between samplings
+ * @aggr_int:		time interval between aggregations
+ * @nr_reg:		number of regions
+ *
+ * This function should not be called while the kdamond is running.
+ * Every time interval is in micro-seconds.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long nr_reg)
+{
+	if (nr_reg < 3) {
+		pr_err("nr_regions (%lu) must be at least 3\n",
+				nr_reg);
+		return -EINVAL;
+	}
+
+	ctx->sample_interval = sample_int;
+	ctx->aggr_interval = aggr_int;
+	ctx->nr_regions = nr_reg;
+
+	return 0;
+}
+
 /*
  * Functions for the module loading/unloading
  */
-- 
2.17.1

[PATCH v17 04/15] mm/damon: Adaptively adjust regions

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

Even somehow the initial monitoring target regions are well constructed
to fulfill the assumption (pages in same region have similar access
frequencies), the data access pattern can be dynamically changed.  This
will result in low monitoring quality.  To keep the assumption as much
as possible, DAMON adaptively merges and splits each region based on
their access frequency.

For each ``aggregation interval``, it compares the access frequencies of
adjacent regions and merges those if the frequency difference is small.
Then, after it reports and clears the aggregated access frequency of
each region, it splits each region into two or three regions if the
total number of regions will not exceed the user-specified maximum
number of regions after the split.

In this way, DAMON provides its best-effort quality and minimal overhead
while keeping the upper-bound overhead that users set.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  11 ++-
 mm/damon.c            | 191 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 189 insertions(+), 13 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 7adc7b6b3507..97ddc74e207f 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -61,7 +61,8 @@ struct damon_task {
  *
  * @sample_interval:		The time between access samplings.
  * @aggr_interval:		The time between monitor results aggregations.
- * @nr_regions:			The number of monitoring regions.
+ * @min_nr_regions:		The minimum number of monitoring regions.
+ * @max_nr_regions:		The maximum number of monitoring regions.
  *
  * For each @sample_interval, DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
@@ -114,7 +115,8 @@ struct damon_task {
 struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
-	unsigned long nr_regions;
+	unsigned long min_nr_regions;
+	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;
 
@@ -133,8 +135,9 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
-		unsigned long aggr_int, unsigned long min_nr_reg);
+int damon_set_attrs(struct damon_ctx *ctx,
+		unsigned long sample_int, unsigned long aggr_int,
+		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
 
diff --git a/mm/damon.c b/mm/damon.c
index 5d0b3ab684b3..d9d0b69d00f5 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -176,6 +176,26 @@ static unsigned int nr_damon_regions(struct damon_task *t)
 	return nr_regions;
 }
 
+/* Returns the size upper limit for each monitoring region */
+static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+	unsigned long sz = 0;
+
+	damon_for_each_task(t, ctx) {
+		damon_for_each_region(r, t)
+			sz += r->ar.end - r->ar.start;
+	}
+
+	if (ctx->min_nr_regions)
+		sz /= ctx->min_nr_regions;
+	if (sz < MIN_REGION)
+		sz = MIN_REGION;
+
+	return sz;
+}
+
 /*
  * Functions for DAMON core logics and features
  */
@@ -226,6 +246,145 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 	}
 }
 
+#define sz_damon_region(r) (r->ar.end - r->ar.start)
+
+/*
+ * Merge two adjacent regions into one region
+ */
+static void damon_merge_two_regions(struct damon_region *l,
+				struct damon_region *r)
+{
+	l->nr_accesses = (l->nr_accesses * sz_damon_region(l) +
+			r->nr_accesses * sz_damon_region(r)) /
+			(sz_damon_region(l) + sz_damon_region(r));
+	l->ar.end = r->ar.end;
+	damon_destroy_region(r);
+}
+
+#define diff_of(a, b) (a > b ? a - b : b - a)
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * t		task affected by merge operation
+ * thres	'->nr_accesses' diff threshold for the merge
+ * sz_limit	size upper limit of each region
+ */
+static void damon_merge_regions_of(struct damon_task *t, unsigned int thres,
+				   unsigned long sz_limit)
+{
+	struct damon_region *r, *prev = NULL, *next;
+
+	damon_for_each_region_safe(r, next, t) {
+		if (prev && prev->ar.end == r->ar.start &&
+		    diff_of(prev->nr_accesses, r->nr_accesses) <= thres &&
+		    sz_damon_region(prev) + sz_damon_region(r) <= sz_limit)
+			damon_merge_two_regions(prev, r);
+		else
+			prev = r;
+	}
+}
+
+/*
+ * Merge adjacent regions having similar access frequencies
+ *
+ * threshold	'->nr_accesses' diff threshold for the merge
+ * sz_limit	size upper limit of each region
+ *
+ * This function merges monitoring target regions which are adjacent and their
+ * access frequencies are similar.  This is for minimizing the monitoring
+ * overhead under the dynamically changeable access pattern.  If a merge was
+ * unnecessarily made, later 'kdamond_split_regions()' will revert it.
+ */
+static void kdamond_merge_regions(struct damon_ctx *c, unsigned int threshold,
+				  unsigned long sz_limit)
+{
+	struct damon_task *t;
+
+	damon_for_each_task(t, c)
+		damon_merge_regions_of(t, threshold, sz_limit);
+}
+
+/*
+ * Split a region in two
+ *
+ * r		the region to be split
+ * sz_r		size of the first sub-region that will be made
+ */
+static void damon_split_region_at(struct damon_ctx *ctx,
+				  struct damon_region *r, unsigned long sz_r)
+{
+	struct damon_region *new;
+
+	new = damon_new_region(r->ar.start + sz_r, r->ar.end);
+	r->ar.end = new->ar.start;
+
+	damon_insert_region(new, r, damon_next_region(r));
+}
+
+/* Split every region in the given task into 'nr_subs' regions */
+static void damon_split_regions_of(struct damon_ctx *ctx,
+				     struct damon_task *t, int nr_subs)
+{
+	struct damon_region *r, *next;
+	unsigned long sz_region, sz_sub = 0;
+	int i;
+
+	damon_for_each_region_safe(r, next, t) {
+		sz_region = r->ar.end - r->ar.start;
+
+		for (i = 0; i < nr_subs - 1 &&
+				sz_region > 2 * MIN_REGION; i++) {
+			/*
+			 * Randomly select size of left sub-region to be at
+			 * least 10 percent and at most 90% of original region
+			 */
+			sz_sub = ALIGN_DOWN(damon_rand(1, 10) *
+					sz_region / 10, MIN_REGION);
+			/* Do not allow blank region */
+			if (sz_sub == 0 || sz_sub >= sz_region)
+				continue;
+
+			damon_split_region_at(ctx, r, sz_sub);
+			sz_region = sz_sub;
+		}
+	}
+}
+
+/*
+ * Split every target region into randomly-sized small regions
+ *
+ * This function splits every target region into random-sized small regions if
+ * current total number of the regions is equal or smaller than half of the
+ * user-specified maximum number of regions.  This is for maximizing the
+ * monitoring accuracy under the dynamically changeable access patterns.  If a
+ * split was unnecessarily made, later 'kdamond_merge_regions()' will revert
+ * it.
+ */
+static void kdamond_split_regions(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	unsigned int nr_regions = 0;
+	static unsigned int last_nr_regions;
+	int nr_subregions = 2;
+
+	damon_for_each_task(t, ctx)
+		nr_regions += nr_damon_regions(t);
+
+	if (nr_regions > ctx->max_nr_regions / 2)
+		return;
+
+	/* Maybe the middle of the region has different access frequency */
+	if (last_nr_regions == nr_regions &&
+			nr_regions < ctx->max_nr_regions / 3)
+		nr_subregions = 3;
+
+	damon_for_each_task(t, ctx)
+		damon_split_regions_of(ctx, t, nr_subregions);
+
+	last_nr_regions = nr_regions;
+}
+
 /*
  * Check whether current monitoring should be stopped
  *
@@ -269,10 +428,14 @@ static int kdamond_fn(void *data)
 	struct damon_ctx *ctx = (struct damon_ctx *)data;
 	struct damon_task *t;
 	struct damon_region *r, *next;
+	unsigned int max_nr_accesses = 0;
+	unsigned long sz_limit = 0;
 
 	pr_info("kdamond (%d) starts\n", ctx->kdamond->pid);
 	if (ctx->init_target_regions)
 		ctx->init_target_regions(ctx);
+	sz_limit = damon_region_sz_limit(ctx);
+
 	while (!kdamond_need_stop(ctx)) {
 		if (ctx->prepare_access_checks)
 			ctx->prepare_access_checks(ctx);
@@ -282,14 +445,16 @@ static int kdamond_fn(void *data)
 		usleep_range(ctx->sample_interval, ctx->sample_interval + 1);
 
 		if (ctx->check_accesses)
-			ctx->check_accesses(ctx);
+			max_nr_accesses = ctx->check_accesses(ctx);
 
 		if (kdamond_aggregate_interval_passed(ctx)) {
 			if (ctx->aggregate_cb)
 				ctx->aggregate_cb(ctx);
+			kdamond_merge_regions(ctx, max_nr_accesses / 10,
+					sz_limit);
 			kdamond_reset_aggregated(ctx);
+			kdamond_split_regions(ctx);
 		}
-
 	}
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
@@ -398,25 +563,33 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  * @ctx:		monitoring context
  * @sample_int:		time interval between samplings
  * @aggr_int:		time interval between aggregations
- * @nr_reg:		number of regions
+ * @min_nr_reg:		minimal number of regions
+ * @max_nr_reg:		maximum number of regions
  *
  * This function should not be called while the kdamond is running.
  * Every time interval is in micro-seconds.
  *
  * Return: 0 on success, negative error code otherwise.
  */
-int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
-		unsigned long aggr_int, unsigned long nr_reg)
+int damon_set_attrs(struct damon_ctx *ctx,
+		    unsigned long sample_int, unsigned long aggr_int,
+		    unsigned long min_nr_reg, unsigned long max_nr_reg)
 {
-	if (nr_reg < 3) {
-		pr_err("nr_regions (%lu) must be at least 3\n",
-				nr_reg);
+	if (min_nr_reg < 3) {
+		pr_err("min_nr_regions (%lu) must be at least 3\n",
+				min_nr_reg);
+		return -EINVAL;
+	}
+	if (min_nr_reg > max_nr_reg) {
+		pr_err("invalid nr_regions.  min (%lu) > max (%lu)\n",
+				min_nr_reg, max_nr_reg);
 		return -EINVAL;
 	}
 
 	ctx->sample_interval = sample_int;
 	ctx->aggr_interval = aggr_int;
-	ctx->nr_regions = nr_reg;
+	ctx->min_nr_regions = min_nr_reg;
+	ctx->max_nr_regions = max_nr_reg;
 
 	return 0;
 }
-- 
2.17.1

[PATCH v17 05/15] mm/damon: Track dynamic monitoring target regions update

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

The monitoring target address range can be dynamically changed.  For
example, virtual memory could be dynamically mapped and unmapped.
Physical memory could be hot-plugged.

As the changes could be quite frequent in some cases, DAMON checks the
dynamic memory mapping changes and applies it to the abstracted target
area only for each of a user-specified time interval, ``regions update
interval``.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h | 20 +++++++++++++++-----
 mm/damon.c            | 23 +++++++++++++++++++++--
 2 files changed, 36 insertions(+), 7 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 97ddc74e207f..3c0b92a679e8 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -61,13 +61,16 @@ struct damon_task {
  *
  * @sample_interval:		The time between access samplings.
  * @aggr_interval:		The time between monitor results aggregations.
+ * @regions_update_interval:	The time between monitor regions updates.
  * @min_nr_regions:		The minimum number of monitoring regions.
  * @max_nr_regions:		The maximum number of monitoring regions.
  *
  * For each @sample_interval, DAMON checks whether each region is accessed or
  * not.  It aggregates and keeps the access information (number of accesses to
- * each region) for @aggr_interval time.  All time intervals are in
- * micro-seconds.
+ * each region) for @aggr_interval time.  DAMON also checks whether the target
+ * memory regions need update (e.g., by ``mmap()`` calls from the application,
+ * in case of virtual memory monitoring) and applies the changes for each
+ * @regions_update_interval.  All time intervals are in micro-seconds.
  *
  * @kdamond:		Kernel thread who does the monitoring.
  * @kdamond_stop:	Notifies whether kdamond should stop.
@@ -88,6 +91,7 @@ struct damon_task {
  * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
  *
  * @init_target_regions:	Constructs initial monitoring target regions.
+ * @update_target_regions:	Updates monitoring target regions.
  * @prepare_access_checks:	Prepares next access check of target regions.
  * @check_accesses:		Checks the access of target regions.
  * @sample_cb:			Called for each sampling interval.
@@ -96,11 +100,14 @@ struct damon_task {
  * DAMON can be extended for various address spaces by users.  For this, users
  * can register the target address space dependent low level functions for
  * their usecases via the callback pointers of the context.  The monitoring
- * thread calls @init_target_regions before starting the monitoring, and
+ * thread calls @init_target_regions before starting the monitoring,
+ * @update_target_regions for each @regions_update_interval, and
  * @prepare_access_checks and @check_accesses for each @sample_interval.
  *
  * @init_target_regions should construct proper monitoring target regions and
  * link those to the DAMON context struct.
+ * @update_target_regions should update the monitoring target regions for
+ * current status.
  * @prepare_access_checks should manipulate the monitoring regions to be
  * prepare for the next access check.
  * @check_accesses should check the accesses to each region that made after the
@@ -115,10 +122,12 @@ struct damon_task {
 struct damon_ctx {
 	unsigned long sample_interval;
 	unsigned long aggr_interval;
+	unsigned long regions_update_interval;
 	unsigned long min_nr_regions;
 	unsigned long max_nr_regions;
 
 	struct timespec64 last_aggregation;
+	struct timespec64 last_regions_update;
 
 	struct task_struct *kdamond;
 	bool kdamond_stop;
@@ -128,6 +137,7 @@ struct damon_ctx {
 
 	/* callbacks */
 	void (*init_target_regions)(struct damon_ctx *context);
+	void (*update_target_regions)(struct damon_ctx *context);
 	void (*prepare_access_checks)(struct damon_ctx *context);
 	unsigned int (*check_accesses)(struct damon_ctx *context);
 	void (*sample_cb)(struct damon_ctx *context);
@@ -135,8 +145,8 @@ struct damon_ctx {
 };
 
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
-int damon_set_attrs(struct damon_ctx *ctx,
-		unsigned long sample_int, unsigned long aggr_int,
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
diff --git a/mm/damon.c b/mm/damon.c
index d9d0b69d00f5..b8a021af50c6 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -385,6 +385,17 @@ static void kdamond_split_regions(struct damon_ctx *ctx)
 	last_nr_regions = nr_regions;
 }
 
+/*
+ * Check whether it is time to check and apply the target monitoring regions
+ *
+ * Returns true if it is.
+ */
+static bool kdamond_need_update_regions(struct damon_ctx *ctx)
+{
+	return damon_check_reset_time_interval(&ctx->last_regions_update,
+			ctx->regions_update_interval);
+}
+
 /*
  * Check whether current monitoring should be stopped
  *
@@ -455,6 +466,12 @@ static int kdamond_fn(void *data)
 			kdamond_reset_aggregated(ctx);
 			kdamond_split_regions(ctx);
 		}
+
+		if (kdamond_need_update_regions(ctx)) {
+			if (ctx->update_target_regions)
+				ctx->update_target_regions(ctx);
+			sz_limit = damon_region_sz_limit(ctx);
+		}
 	}
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
@@ -562,6 +579,7 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  * damon_set_attrs() - Set attributes for the monitoring.
  * @ctx:		monitoring context
  * @sample_int:		time interval between samplings
+ * @regions_update_int:	time interval between target regions update
  * @aggr_int:		time interval between aggregations
  * @min_nr_reg:		minimal number of regions
  * @max_nr_reg:		maximum number of regions
@@ -571,8 +589,8 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
  *
  * Return: 0 on success, negative error code otherwise.
  */
-int damon_set_attrs(struct damon_ctx *ctx,
-		    unsigned long sample_int, unsigned long aggr_int,
+int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
+		    unsigned long aggr_int, unsigned long regions_update_int,
 		    unsigned long min_nr_reg, unsigned long max_nr_reg)
 {
 	if (min_nr_reg < 3) {
@@ -588,6 +606,7 @@ int damon_set_attrs(struct damon_ctx *ctx,
 
 	ctx->sample_interval = sample_int;
 	ctx->aggr_interval = aggr_int;
+	ctx->regions_update_interval = regions_update_int;
 	ctx->min_nr_regions = min_nr_reg;
 	ctx->max_nr_regions = max_nr_reg;
 
-- 
2.17.1

[PATCH v17 06/15] mm/damon: Implement callbacks for the virtual memory address spaces

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit introduces a reference implementation of the address space
specific low level primitives for the virtual address space.  Now users
can easily monitor the data accesses on virtual address spaces of
specific processes by simply configuring the implementation to be used
by DAMON.

PTE Accessed-bit Based Access Check
-----------------------------------

The implementation uses PTE Accessed-bit for basic access checks.  That
is, it clears the bit for next sampling target page and checks whether
it set again after one sampling period.  To avoid disturbing other
Accessed bit users such as the reclamation logic, the implementation
adjusts the ``PG_Idle`` and ``PG_Young`` appropriately, as same to the
'Idle Page Tracking'.

VMA-based Target Address Range Construction
-------------------------------------------

Only small parts in the super-huge virtual address space of the
processes are mapped to physical memory and accessed.  Thus, tracking
the unmapped address regions is just wasteful.  However, because DAMON
can deal with some level of noise using the adaptive regions adjustment
mechanism, tracking every mapping is not strictly required but could
even incur a high overhead in some cases.  That said, too huge unmapped
areas inside the monitoring target should be removed to not take the
time for the adaptive mechanism.

For the reason, this implementation converts the complex mappings to
three distinct regions that cover every mapped area of the address
space.  Also, the two gaps between the three regions are the two biggest
unmapped areas in the given address space.  The two biggest unmapped
areas would be the gap between the heap and the uppermost mmap()-ed
region, and the gap between the lowermost mmap()-ed region and the stack
in most of the cases.  Because these gaps are exceptionally huge in
usual address spacees, excluding these will be sufficient to make a
reasonable trade-off.  Below shows this in detail::

    <heap>
    <BIG UNMAPPED REGION 1>
    <uppermost mmap()-ed region>
    (small mmap()-ed regions and munmap()-ed regions)
    <lowermost mmap()-ed region>
    <BIG UNMAPPED REGION 2>
    <stack>

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |   6 +
 mm/damon.c            | 474 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 480 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 3c0b92a679e8..310d36d123b3 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -144,6 +144,12 @@ struct damon_ctx {
 	void (*aggregate_cb)(struct damon_ctx *context);
 };
 
+/* Reference callback implementations for virtual memory */
+void kdamond_init_vm_regions(struct damon_ctx *ctx);
+void kdamond_update_vm_regions(struct damon_ctx *ctx);
+void kdamond_prepare_vm_access_checks(struct damon_ctx *ctx);
+unsigned int kdamond_check_vm_accesses(struct damon_ctx *ctx);
+
 int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 		unsigned long aggr_int, unsigned long regions_update_int,
diff --git a/mm/damon.c b/mm/damon.c
index b8a021af50c6..7e0e42d7e1ec 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -9,6 +9,9 @@
  * This file is constructed in below parts.
  *
  * - Functions and macros for DAMON data structures
+ * - Functions for the initial monitoring target regions construction
+ * - Functions for the dynamic monitoring target regions update
+ * - Functions for the access checking of the regions
  * - Functions for DAMON core logics and features
  * - Functions for the DAMON programming interface
  * - Functions for the module loading/unloading
@@ -196,6 +199,477 @@ static unsigned long damon_region_sz_limit(struct damon_ctx *ctx)
 	return sz;
 }
 
+/*
+ * Get the mm_struct of the given task
+ *
+ * Caller _must_ put the mm_struct after use, unless it is NULL.
+ *
+ * Returns the mm_struct of the task on success, NULL on failure
+ */
+static struct mm_struct *damon_get_mm(struct damon_task *t)
+{
+	struct task_struct *task;
+	struct mm_struct *mm;
+
+	task = damon_get_task_struct(t);
+	if (!task)
+		return NULL;
+
+	mm = get_task_mm(task);
+	put_task_struct(task);
+	return mm;
+}
+
+/*
+ * Functions for the initial monitoring target regions construction
+ */
+
+/*
+ * Size-evenly split a region into 'nr_pieces' small regions
+ *
+ * Returns 0 on success, or negative error code otherwise.
+ */
+static int damon_split_region_evenly(struct damon_ctx *ctx,
+		struct damon_region *r, unsigned int nr_pieces)
+{
+	unsigned long sz_orig, sz_piece, orig_end;
+	struct damon_region *n = NULL, *next;
+	unsigned long start;
+
+	if (!r || !nr_pieces)
+		return -EINVAL;
+
+	orig_end = r->ar.end;
+	sz_orig = r->ar.end - r->ar.start;
+	sz_piece = ALIGN_DOWN(sz_orig / nr_pieces, MIN_REGION);
+
+	if (!sz_piece)
+		return -EINVAL;
+
+	r->ar.end = r->ar.start + sz_piece;
+	next = damon_next_region(r);
+	for (start = r->ar.end; start + sz_piece <= orig_end;
+			start += sz_piece) {
+		n = damon_new_region(start, start + sz_piece);
+		if (!n)
+			return -ENOMEM;
+		damon_insert_region(n, r, next);
+		r = n;
+	}
+	/* complement last region for possible rounding error */
+	if (n)
+		n->ar.end = orig_end;
+
+	return 0;
+}
+
+static unsigned long sz_range(struct damon_addr_range *r)
+{
+	return r->end - r->start;
+}
+
+static void swap_ranges(struct damon_addr_range *r1,
+			struct damon_addr_range *r2)
+{
+	struct damon_addr_range tmp;
+
+	tmp = *r1;
+	*r1 = *r2;
+	*r2 = tmp;
+}
+
+/*
+ * Find three regions separated by two biggest unmapped regions
+ *
+ * vma		the head vma of the target address space
+ * regions	an array of three address ranges that results will be saved
+ *
+ * This function receives an address space and finds three regions in it which
+ * separated by the two biggest unmapped regions in the space.  Please refer to
+ * below comments of 'damon_init_vm_regions_of()' function to know why this is
+ * necessary.
+ *
+ * Returns 0 if success, or negative error code otherwise.
+ */
+static int damon_three_regions_in_vmas(struct vm_area_struct *vma,
+				       struct damon_addr_range regions[3])
+{
+	struct damon_addr_range gap = {0}, first_gap = {0}, second_gap = {0};
+	struct vm_area_struct *last_vma = NULL;
+	unsigned long start = 0;
+	struct rb_root rbroot;
+
+	/* Find two biggest gaps so that first_gap > second_gap > others */
+	for (; vma; vma = vma->vm_next) {
+		if (!last_vma) {
+			start = vma->vm_start;
+			goto next;
+		}
+
+		if (vma->rb_subtree_gap <= sz_range(&second_gap)) {
+			rbroot.rb_node = &vma->vm_rb;
+			vma = rb_entry(rb_last(&rbroot),
+					struct vm_area_struct, vm_rb);
+			goto next;
+		}
+
+		gap.start = last_vma->vm_end;
+		gap.end = vma->vm_start;
+		if (sz_range(&gap) > sz_range(&second_gap)) {
+			swap_ranges(&gap, &second_gap);
+			if (sz_range(&second_gap) > sz_range(&first_gap))
+				swap_ranges(&second_gap, &first_gap);
+		}
+next:
+		last_vma = vma;
+	}
+
+	if (!sz_range(&second_gap) || !sz_range(&first_gap))
+		return -EINVAL;
+
+	/* Sort the two biggest gaps by address */
+	if (first_gap.start > second_gap.start)
+		swap_ranges(&first_gap, &second_gap);
+
+	/* Store the result */
+	regions[0].start = ALIGN(start, MIN_REGION);
+	regions[0].end = ALIGN(first_gap.start, MIN_REGION);
+	regions[1].start = ALIGN(first_gap.end, MIN_REGION);
+	regions[1].end = ALIGN(second_gap.start, MIN_REGION);
+	regions[2].start = ALIGN(second_gap.end, MIN_REGION);
+	regions[2].end = ALIGN(last_vma->vm_end, MIN_REGION);
+
+	return 0;
+}
+
+/*
+ * Get the three regions in the given task
+ *
+ * Returns 0 on success, negative error code otherwise.
+ */
+static int damon_three_regions_of(struct damon_task *t,
+				struct damon_addr_range regions[3])
+{
+	struct mm_struct *mm;
+	int rc;
+
+	mm = damon_get_mm(t);
+	if (!mm)
+		return -EINVAL;
+
+	down_read(&mm->mmap_sem);
+	rc = damon_three_regions_in_vmas(mm->mmap, regions);
+	up_read(&mm->mmap_sem);
+
+	mmput(mm);
+	return rc;
+}
+
+/*
+ * Initialize the monitoring target regions for the given task
+ *
+ * t	the given target task
+ *
+ * Because only a number of small portions of the entire address space
+ * is actually mapped to the memory and accessed, monitoring the unmapped
+ * regions is wasteful.  That said, because we can deal with small noises,
+ * tracking every mapping is not strictly required but could even incur a high
+ * overhead if the mapping frequently changes or the number of mappings is
+ * high.  The adaptive regions adjustment mechanism will further help to deal
+ * with the noise by simply identifying the unmapped areas as a region that
+ * has no access.  Moreover, applying the real mappings that would have many
+ * unmapped areas inside will make the adaptive mechanism quite complex.  That
+ * said, too huge unmapped areas inside the monitoring target should be removed
+ * to not take the time for the adaptive mechanism.
+ *
+ * For the reason, we convert the complex mappings to three distinct regions
+ * that cover every mapped area of the address space.  Also the two gaps
+ * between the three regions are the two biggest unmapped areas in the given
+ * address space.  In detail, this function first identifies the start and the
+ * end of the mappings and the two biggest unmapped areas of the address space.
+ * Then, it constructs the three regions as below:
+ *
+ *     [mappings[0]->start, big_two_unmapped_areas[0]->start)
+ *     [big_two_unmapped_areas[0]->end, big_two_unmapped_areas[1]->start)
+ *     [big_two_unmapped_areas[1]->end, mappings[nr_mappings - 1]->end)
+ *
+ * As usual memory map of processes is as below, the gap between the heap and
+ * the uppermost mmap()-ed region, and the gap between the lowermost mmap()-ed
+ * region and the stack will be two biggest unmapped regions.  Because these
+ * gaps are exceptionally huge areas in usual address space, excluding these
+ * two biggest unmapped regions will be sufficient to make a trade-off.
+ *
+ *   <heap>
+ *   <BIG UNMAPPED REGION 1>
+ *   <uppermost mmap()-ed region>
+ *   (other mmap()-ed regions and small unmapped regions)
+ *   <lowermost mmap()-ed region>
+ *   <BIG UNMAPPED REGION 2>
+ *   <stack>
+ */
+static void damon_init_vm_regions_of(struct damon_ctx *c, struct damon_task *t)
+{
+	struct damon_region *r;
+	struct damon_addr_range regions[3];
+	unsigned long sz = 0, nr_pieces;
+	int i;
+
+	if (damon_three_regions_of(t, regions)) {
+		pr_err("Failed to get three regions of task %d\n", t->pid);
+		return;
+	}
+
+	for (i = 0; i < 3; i++)
+		sz += regions[i].end - regions[i].start;
+	if (c->min_nr_regions)
+		sz /= c->min_nr_regions;
+	if (sz < MIN_REGION)
+		sz = MIN_REGION;
+
+	/* Set the initial three regions of the task */
+	for (i = 0; i < 3; i++) {
+		r = damon_new_region(regions[i].start, regions[i].end);
+		if (!r) {
+			pr_err("%d'th init region creation failed\n", i);
+			return;
+		}
+		damon_add_region(r, t);
+
+		nr_pieces = (regions[i].end - regions[i].start) / sz;
+		damon_split_region_evenly(c, r, nr_pieces);
+	}
+}
+
+/* Initialize '->regions_list' of every task */
+void kdamond_init_vm_regions(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+
+	damon_for_each_task(t, ctx) {
+		/* the user may set the target regions as they want */
+		if (!nr_damon_regions(t))
+			damon_init_vm_regions_of(ctx, t);
+	}
+}
+
+/*
+ * Functions for the dynamic monitoring target regions update
+ */
+
+/*
+ * Check whether a region is intersecting an address range
+ *
+ * Returns true if it is.
+ */
+static bool damon_intersect(struct damon_region *r, struct damon_addr_range *re)
+{
+	return !(r->ar.end <= re->start || re->end <= r->ar.start);
+}
+
+/*
+ * Update damon regions for the three big regions of the given task
+ *
+ * t		the given task
+ * bregions	the three big regions of the task
+ */
+static void damon_apply_three_regions(struct damon_ctx *ctx,
+		struct damon_task *t, struct damon_addr_range bregions[3])
+{
+	struct damon_region *r, *next;
+	unsigned int i = 0;
+
+	/* Remove regions which are not in the three big regions now */
+	damon_for_each_region_safe(r, next, t) {
+		for (i = 0; i < 3; i++) {
+			if (damon_intersect(r, &bregions[i]))
+				break;
+		}
+		if (i == 3)
+			damon_destroy_region(r);
+	}
+
+	/* Adjust intersecting regions to fit with the three big regions */
+	for (i = 0; i < 3; i++) {
+		struct damon_region *first = NULL, *last;
+		struct damon_region *newr;
+		struct damon_addr_range *br;
+
+		br = &bregions[i];
+		/* Get the first and last regions which intersects with br */
+		damon_for_each_region(r, t) {
+			if (damon_intersect(r, br)) {
+				if (!first)
+					first = r;
+				last = r;
+			}
+			if (r->ar.start >= br->end)
+				break;
+		}
+		if (!first) {
+			/* no damon_region intersects with this big region */
+			newr = damon_new_region(
+					ALIGN_DOWN(br->start, MIN_REGION),
+					ALIGN(br->end, MIN_REGION));
+			if (!newr)
+				continue;
+			damon_insert_region(newr, damon_prev_region(r), r);
+		} else {
+			first->ar.start = ALIGN_DOWN(br->start, MIN_REGION);
+			last->ar.end = ALIGN(br->end, MIN_REGION);
+		}
+	}
+}
+
+/*
+ * Update regions for current memory mappings
+ */
+void kdamond_update_vm_regions(struct damon_ctx *ctx)
+{
+	struct damon_addr_range three_regions[3];
+	struct damon_task *t;
+
+	damon_for_each_task(t, ctx) {
+		if (damon_three_regions_of(t, three_regions))
+			continue;
+		damon_apply_three_regions(ctx, t, three_regions);
+	}
+}
+
+/*
+ * Functions for the access checking of the regions
+ */
+
+static void damon_mkold(struct mm_struct *mm, unsigned long addr)
+{
+	pte_t *pte = NULL;
+	pmd_t *pmd = NULL;
+	spinlock_t *ptl;
+
+	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
+		return;
+
+	if (pte) {
+		if (pte_young(*pte)) {
+			clear_page_idle(pte_page(*pte));
+			set_page_young(pte_page(*pte));
+		}
+		*pte = pte_mkold(*pte);
+		pte_unmap_unlock(pte, ptl);
+		return;
+	}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	if (pmd_young(*pmd)) {
+		clear_page_idle(pmd_page(*pmd));
+		set_page_young(pmd_page(*pmd));
+	}
+	*pmd = pmd_mkold(*pmd);
+	spin_unlock(ptl);
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
+}
+
+static void damon_prepare_vm_access_check(struct damon_ctx *ctx,
+			struct mm_struct *mm, struct damon_region *r)
+{
+	r->sampling_addr = damon_rand(r->ar.start, r->ar.end);
+
+	damon_mkold(mm, r->sampling_addr);
+}
+
+void kdamond_prepare_vm_access_checks(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+
+	damon_for_each_task(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		damon_for_each_region(r, t)
+			damon_prepare_vm_access_check(ctx, mm, r);
+		mmput(mm);
+	}
+}
+
+static bool damon_young(struct mm_struct *mm, unsigned long addr,
+			unsigned long *page_sz)
+{
+	pte_t *pte = NULL;
+	pmd_t *pmd = NULL;
+	spinlock_t *ptl;
+	bool young = false;
+
+	if (follow_pte_pmd(mm, addr, NULL, &pte, &pmd, &ptl))
+		return false;
+
+	*page_sz = PAGE_SIZE;
+	if (pte) {
+		young = pte_young(*pte);
+		pte_unmap_unlock(pte, ptl);
+		return young;
+	}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	young = pmd_young(*pmd);
+	spin_unlock(ptl);
+	*page_sz = ((1UL) << HPAGE_PMD_SHIFT);
+#endif	/* CONFIG_TRANSPARENT_HUGEPAGE */
+
+	return young;
+}
+
+/*
+ * Check whether the region was accessed after the last preparation
+ *
+ * mm	'mm_struct' for the given virtual address space
+ * r	the region to be checked
+ */
+static void damon_check_vm_access(struct damon_ctx *ctx,
+			       struct mm_struct *mm, struct damon_region *r)
+{
+	static struct mm_struct *last_mm;
+	static unsigned long last_addr;
+	static unsigned long last_page_sz = PAGE_SIZE;
+	static bool last_accessed;
+
+	/* If the region is in the last checked page, reuse the result */
+	if (mm == last_mm && (ALIGN_DOWN(last_addr, last_page_sz) ==
+				ALIGN_DOWN(r->sampling_addr, last_page_sz))) {
+		if (last_accessed)
+			r->nr_accesses++;
+		return;
+	}
+
+	last_accessed = damon_young(mm, r->sampling_addr, &last_page_sz);
+	if (last_accessed)
+		r->nr_accesses++;
+
+	last_mm = mm;
+	last_addr = r->sampling_addr;
+}
+
+unsigned int kdamond_check_vm_accesses(struct damon_ctx *ctx)
+{
+	struct damon_task *t;
+	struct mm_struct *mm;
+	struct damon_region *r;
+	unsigned int max_nr_accesses = 0;
+
+	damon_for_each_task(t, ctx) {
+		mm = damon_get_mm(t);
+		if (!mm)
+			continue;
+		damon_for_each_region(r, t) {
+			damon_check_vm_access(ctx, mm, r);
+			max_nr_accesses = max(r->nr_accesses, max_nr_accesses);
+		}
+		mmput(mm);
+	}
+
+	return max_nr_accesses;
+}
+
 /*
  * Functions for DAMON core logics and features
  */
-- 
2.17.1

[PATCH v17 07/15] mm/damon: Implement access pattern recording

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements the recording feature of DAMON.  If this feature
is enabled, DAMON writes the monitored access patterns in its binary
format into a file which specified by the user.  This is already able to
be implemented by each user using the callbacks.  However, as the
recording is expected to be widely used, this commit implements the
feature in the DAMON, for more convenience.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/linux/damon.h |  15 +++++
 mm/damon.c            | 141 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 153 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 310d36d123b3..b0e7e31a22b3 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -72,6 +72,14 @@ struct damon_task {
  * in case of virtual memory monitoring) and applies the changes for each
  * @regions_update_interval.  All time intervals are in micro-seconds.
  *
+ * @rbuf: In-memory buffer for monitoring result recording.
+ * @rbuf_len: The length of @rbuf.
+ * @rbuf_offset: The offset for next write to @rbuf.
+ * @rfile_path: Record file path.
+ *
+ * If @rbuf, @rbuf_len, and @rfile_path are set, the monitored results are
+ * automatically stored in @rfile_path file.
+ *
  * @kdamond:		Kernel thread who does the monitoring.
  * @kdamond_stop:	Notifies whether kdamond should stop.
  * @kdamond_lock:	Mutex for the synchronizations with @kdamond.
@@ -129,6 +137,11 @@ struct damon_ctx {
 	struct timespec64 last_aggregation;
 	struct timespec64 last_regions_update;
 
+	unsigned char *rbuf;
+	unsigned int rbuf_len;
+	unsigned int rbuf_offset;
+	char *rfile_path;
+
 	struct task_struct *kdamond;
 	bool kdamond_stop;
 	struct mutex kdamond_lock;
@@ -154,6 +167,8 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids);
 int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 		unsigned long aggr_int, unsigned long regions_update_int,
 		unsigned long min_nr_reg, unsigned long max_nr_reg);
+int damon_set_recording(struct damon_ctx *ctx,
+				unsigned int rbuf_len, char *rfile_path);
 int damon_start(struct damon_ctx *ctx);
 int damon_stop(struct damon_ctx *ctx);
 
diff --git a/mm/damon.c b/mm/damon.c
index 7e0e42d7e1ec..be8be4626400 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -58,6 +58,10 @@
 #define damon_for_each_task_safe(t, next, ctx) \
 	list_for_each_entry_safe(t, next, &(ctx)->tasks_list, list)
 
+#define MIN_RECORD_BUFFER_LEN	1024
+#define MAX_RECORD_BUFFER_LEN	(4 * 1024 * 1024)
+#define MAX_RFILE_PATH_LEN	256
+
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32() % (r - l))
 
@@ -707,16 +711,88 @@ static bool kdamond_aggregate_interval_passed(struct damon_ctx *ctx)
 }
 
 /*
- * Reset the aggregated monitoring results
+ * Flush the content in the result buffer to the result file
+ */
+static void damon_flush_rbuffer(struct damon_ctx *ctx)
+{
+	ssize_t sz;
+	loff_t pos = 0;
+	struct file *rfile;
+
+	if (!ctx->rbuf_offset)
+		return;
+
+	rfile = filp_open(ctx->rfile_path, O_CREAT | O_RDWR | O_APPEND, 0644);
+	if (IS_ERR(rfile)) {
+		pr_err("Cannot open the result file %s\n",
+				ctx->rfile_path);
+		return;
+	}
+
+	while (ctx->rbuf_offset) {
+		sz = kernel_write(rfile, ctx->rbuf, ctx->rbuf_offset, &pos);
+		if (sz < 0)
+			break;
+		ctx->rbuf_offset -= sz;
+	}
+	filp_close(rfile, NULL);
+}
+
+/*
+ * Write a data into the result buffer
+ */
+static void damon_write_rbuf(struct damon_ctx *ctx, void *data, ssize_t size)
+{
+	if (!ctx->rbuf_len || !ctx->rbuf || !ctx->rfile_path)
+		return;
+	if (ctx->rbuf_offset + size > ctx->rbuf_len)
+		damon_flush_rbuffer(ctx);
+	if (ctx->rbuf_offset + size > ctx->rbuf_len) {
+		pr_warn("%s: flush failed, or wrong size given(%u, %zu)\n",
+				__func__, ctx->rbuf_offset, size);
+		return;
+	}
+
+	memcpy(&ctx->rbuf[ctx->rbuf_offset], data, size);
+	ctx->rbuf_offset += size;
+}
+
+/*
+ * Flush the aggregated monitoring results to the result buffer
+ *
+ * Stores current tracking results to the result buffer and reset 'nr_accesses'
+ * of each region.  The format for the result buffer is as below:
+ *
+ *   <time> <number of tasks> <array of task infos>
+ *
+ *   task info: <pid> <number of regions> <array of region infos>
+ *   region info: <start address> <end address> <nr_accesses>
  */
 static void kdamond_reset_aggregated(struct damon_ctx *c)
 {
 	struct damon_task *t;
-	struct damon_region *r;
+	struct timespec64 now;
+	unsigned int nr;
+
+	ktime_get_coarse_ts64(&now);
+
+	damon_write_rbuf(c, &now, sizeof(now));
+	nr = nr_damon_tasks(c);
+	damon_write_rbuf(c, &nr, sizeof(nr));
 
 	damon_for_each_task(t, c) {
-		damon_for_each_region(r, t)
+		struct damon_region *r;
+
+		damon_write_rbuf(c, &t->pid, sizeof(t->pid));
+		nr = nr_damon_regions(t);
+		damon_write_rbuf(c, &nr, sizeof(nr));
+		damon_for_each_region(r, t) {
+			damon_write_rbuf(c, &r->ar.start, sizeof(r->ar.start));
+			damon_write_rbuf(c, &r->ar.end, sizeof(r->ar.end));
+			damon_write_rbuf(c, &r->nr_accesses,
+					sizeof(r->nr_accesses));
 			r->nr_accesses = 0;
+		}
 	}
 }
 
@@ -905,6 +981,14 @@ static bool kdamond_need_stop(struct damon_ctx *ctx)
 	return true;
 }
 
+static void kdamond_write_record_header(struct damon_ctx *ctx)
+{
+	int recfmt_ver = 1;
+
+	damon_write_rbuf(ctx, "damon_recfmt_ver", 16);
+	damon_write_rbuf(ctx, &recfmt_ver, sizeof(recfmt_ver));
+}
+
 /*
  * The monitoring daemon that runs as a kernel thread
  */
@@ -921,6 +1005,8 @@ static int kdamond_fn(void *data)
 		ctx->init_target_regions(ctx);
 	sz_limit = damon_region_sz_limit(ctx);
 
+	kdamond_write_record_header(ctx);
+
 	while (!kdamond_need_stop(ctx)) {
 		if (ctx->prepare_access_checks)
 			ctx->prepare_access_checks(ctx);
@@ -947,6 +1033,7 @@ static int kdamond_fn(void *data)
 			sz_limit = damon_region_sz_limit(ctx);
 		}
 	}
+	damon_flush_rbuffer(ctx);
 	damon_for_each_task(t, ctx) {
 		damon_for_each_region_safe(r, next, t)
 			damon_destroy_region(r);
@@ -1049,6 +1136,54 @@ int damon_set_pids(struct damon_ctx *ctx, int *pids, ssize_t nr_pids)
 	return 0;
 }
 
+/**
+ * damon_set_recording() - Set attributes for the recording.
+ * @ctx:	target kdamond context
+ * @rbuf_len:	length of the result buffer
+ * @rfile_path:	path to the monitor result files
+ *
+ * Setting 'rbuf_len' 0 disables recording.
+ *
+ * This function should not be called while the kdamond is running.
+ *
+ * Return: 0 on success, negative error code otherwise.
+ */
+int damon_set_recording(struct damon_ctx *ctx,
+			unsigned int rbuf_len, char *rfile_path)
+{
+	size_t rfile_path_len;
+
+	if (rbuf_len && (rbuf_len > MAX_RECORD_BUFFER_LEN ||
+			rbuf_len < MIN_RECORD_BUFFER_LEN)) {
+		pr_err("result buffer size (%u) is out of [%d,%d]\n",
+				rbuf_len, MIN_RECORD_BUFFER_LEN,
+				MAX_RECORD_BUFFER_LEN);
+		return -EINVAL;
+	}
+	rfile_path_len = strnlen(rfile_path, MAX_RFILE_PATH_LEN);
+	if (rfile_path_len >= MAX_RFILE_PATH_LEN) {
+		pr_err("too long (>%d) result file path %s\n",
+				MAX_RFILE_PATH_LEN, rfile_path);
+		return -EINVAL;
+	}
+	ctx->rbuf_len = rbuf_len;
+	kfree(ctx->rbuf);
+	ctx->rbuf = NULL;
+	kfree(ctx->rfile_path);
+	ctx->rfile_path = NULL;
+
+	if (rbuf_len) {
+		ctx->rbuf = kvmalloc(rbuf_len, GFP_KERNEL);
+		if (!ctx->rbuf)
+			return -ENOMEM;
+	}
+	ctx->rfile_path = kmalloc(rfile_path_len + 1, GFP_KERNEL);
+	if (!ctx->rfile_path)
+		return -ENOMEM;
+	strncpy(ctx->rfile_path, rfile_path, rfile_path_len + 1);
+	return 0;
+}
+
 /**
  * damon_set_attrs() - Set attributes for the monitoring.
  * @ctx:		monitoring context
-- 
2.17.1

[PATCH v17 08/15] mm/damon: Add a tracepoint

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a tracepoint for DAMON.  It traces the monitoring
results of each region for each aggregation interval.  Using this, DAMON
can easily integrated with tracepoints supporting tools such as perf.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 include/trace/events/damon.h | 43 ++++++++++++++++++++++++++++++++++++
 mm/damon.c                   |  4 ++++
 2 files changed, 47 insertions(+)
 create mode 100644 include/trace/events/damon.h

diff --git a/include/trace/events/damon.h b/include/trace/events/damon.h
new file mode 100644
index 000000000000..40b249a28b30
--- /dev/null
+++ b/include/trace/events/damon.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM damon
+
+#if !defined(_TRACE_DAMON_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_DAMON_H
+
+#include <linux/damon.h>
+#include <linux/types.h>
+#include <linux/tracepoint.h>
+
+TRACE_EVENT(damon_aggregated,
+
+	TP_PROTO(struct damon_task *t, struct damon_region *r,
+		unsigned int nr_regions),
+
+	TP_ARGS(t, r, nr_regions),
+
+	TP_STRUCT__entry(
+		__field(int, pid)
+		__field(unsigned int, nr_regions)
+		__field(unsigned long, start)
+		__field(unsigned long, end)
+		__field(unsigned int, nr_accesses)
+	),
+
+	TP_fast_assign(
+		__entry->pid = t->pid;
+		__entry->nr_regions = nr_regions;
+		__entry->start = r->ar.start;
+		__entry->end = r->ar.end;
+		__entry->nr_accesses = r->nr_accesses;
+	),
+
+	TP_printk("pid=%d nr_regions=%u %lu-%lu: %u", __entry->pid,
+			__entry->nr_regions, __entry->start,
+			__entry->end, __entry->nr_accesses)
+);
+
+#endif /* _TRACE_DAMON_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/damon.c b/mm/damon.c
index be8be4626400..ce351592fe86 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -19,6 +19,8 @@
 
 #define pr_fmt(fmt) "damon: " fmt
 
+#define CREATE_TRACE_POINTS
+
 #include <linux/damon.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
@@ -29,6 +31,7 @@
 #include <linux/sched/mm.h>
 #include <linux/sched/task.h>
 #include <linux/slab.h>
+#include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
 #define MIN_REGION PAGE_SIZE
@@ -791,6 +794,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 			damon_write_rbuf(c, &r->ar.end, sizeof(r->ar.end));
 			damon_write_rbuf(c, &r->nr_accesses,
 					sizeof(r->nr_accesses));
+			trace_damon_aggregated(t, r, nr);
 			r->nr_accesses = 0;
 		}
 	}
-- 
2.17.1

[PATCH v17 09/15] mm/damon: Implement a debugfs interface

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements a debugfs interface for DAMON.  It works for the
virtual address spaces monitoring.

DAMON exports four files, ``attrs``, ``pids``, ``record``, and
``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.

Attributes
----------

Users can read and write the ``sampling interval``, ``aggregation
interval``, ``regions update interval``, and min/max number of
monitoring target regions by reading from and writing to the ``attrs``
file.  For example, below commands set those values to 5 ms, 100 ms,
1,000 ms, 10, 1000 and check it again::

    # cd <debugfs>/damon
    # echo 5000 100000 1000000 10 1000 > attrs
    # cat attrs
    5000 100000 1000000 10 1000

Target PIDs
-----------

Users can read and write the pids of current monitoring target processes
by reading from and writing to the ``pids`` file.  For example, below
commands set processes having pids 42 and 4242 as the processes to be
monitored and check it again::

    # cd <debugfs>/damon
    # echo 42 4242 > pids
    # cat pids
    42 4242

Note that setting the pids doesn't start the monitoring.

Record
------

DAMON supports direct monitoring result record feature.  The recorded
results are first written to a buffer and flushed to a file in batch.
Users can set the size of the buffer and the path to the result file by
reading from and writing to the ``record`` file.  For example, below
commands set the buffer to be 4 KiB and the result to be saved in
'/damon.data'.

    # cd <debugfs>/damon
    # echo 4096 /damon.data > pids
    # cat record
    4096 /damon.data

Turning On/Off
--------------

You can check current status, start and stop the monitoring by reading
from and writing to the ``monitor_on`` file.  Writing ``on`` to the file
starts DAMON to monitor the target processes with the attributes.
Writing ``off`` to the file stops DAMON.  DAMON also stops if every
target processes is terminated.  Below example commands turn on, off,
and check status of DAMON::

    # cd <debugfs>/damon
    # echo on > monitor_on
    # echo off > monitor_on
    # cat monitor_on
    off

Please note that you cannot write to the ``attrs`` and ``pids`` files
while the monitoring is turned on.  If you write to the files while
DAMON is running, ``-EINVAL`` will be returned.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Leonard Foerster <foersleo@amazon.de>
---
 mm/damon.c | 381 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 380 insertions(+), 1 deletion(-)

diff --git a/mm/damon.c b/mm/damon.c
index ce351592fe86..e99500c9f7c3 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -14,6 +14,7 @@
  * - Functions for the access checking of the regions
  * - Functions for DAMON core logics and features
  * - Functions for the DAMON programming interface
+ * - Functions for the DAMON debugfs interface
  * - Functions for the module loading/unloading
  */
 
@@ -22,6 +23,7 @@
 #define CREATE_TRACE_POINTS
 
 #include <linux/damon.h>
+#include <linux/debugfs.h>
 #include <linux/delay.h>
 #include <linux/kthread.h>
 #include <linux/mm.h>
@@ -68,6 +70,20 @@
 /* Get a random number in [l, r) */
 #define damon_rand(l, r) (l + prandom_u32() % (r - l))
 
+/* A monitoring context for debugfs interface users. */
+static struct damon_ctx damon_user_ctx = {
+	.sample_interval = 5 * 1000,
+	.aggr_interval = 100 * 1000,
+	.regions_update_interval = 1000 * 1000,
+	.min_nr_regions = 10,
+	.max_nr_regions = 1000,
+
+	.init_target_regions = kdamond_init_vm_regions,
+	.update_target_regions = kdamond_update_vm_regions,
+	.prepare_access_checks = kdamond_prepare_vm_access_checks,
+	.check_accesses = kdamond_check_vm_accesses,
+};
+
 /*
  * Construct a damon_region struct
  *
@@ -1226,17 +1242,380 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 	return 0;
 }
 
+/*
+ * Functions for the DAMON debugfs interface
+ */
+
+static ssize_t debugfs_monitor_on_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char monitor_on_buf[5];
+	bool monitor_on;
+	int len;
+
+	monitor_on = damon_kdamond_running(ctx);
+	len = snprintf(monitor_on_buf, 5, monitor_on ? "on\n" : "off\n");
+
+	return simple_read_from_buffer(buf, count, ppos, monitor_on_buf, len);
+}
+
+/*
+ * Returns non-empty string on success, negarive error code otherwise.
+ */
+static char *user_input_str(const char __user *buf, size_t count, loff_t *ppos)
+{
+	char *kbuf;
+	ssize_t ret;
+
+	/* We do not accept continuous write */
+	if (*ppos)
+		return ERR_PTR(-EINVAL);
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);
+	if (!kbuf)
+		return ERR_PTR(-ENOMEM);
+
+	ret = simple_write_to_buffer(kbuf, count + 1, ppos, buf, count);
+	if (ret != count) {
+		kfree(kbuf);
+		return ERR_PTR(-EIO);
+	}
+	kbuf[ret] = '\0';
+
+	return kbuf;
+}
+
+static ssize_t debugfs_monitor_on_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t ret = count;
+	char *kbuf;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	/* Remove white space */
+	if (sscanf(kbuf, "%s", kbuf) != 1)
+		return -EINVAL;
+	if (!strncmp(kbuf, "on", count))
+		err = damon_start(ctx);
+	else if (!strncmp(kbuf, "off", count))
+		err = damon_stop(ctx);
+	else
+		return -EINVAL;
+
+	if (err)
+		ret = err;
+	return ret;
+}
+
+static ssize_t damon_sprint_pids(struct damon_ctx *ctx, char *buf, ssize_t len)
+{
+	struct damon_task *t;
+	int written = 0;
+	int rc;
+
+	damon_for_each_task(t, ctx) {
+		rc = snprintf(&buf[written], len - written, "%d ", t->pid);
+		if (!rc)
+			return -ENOMEM;
+		written += rc;
+	}
+	if (written)
+		written -= 1;
+	written += snprintf(&buf[written], len - written, "\n");
+	return written;
+}
+
+static ssize_t debugfs_pids_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	ssize_t len;
+	char pids_buf[320];
+
+	mutex_lock(&ctx->kdamond_lock);
+	len = damon_sprint_pids(ctx, pids_buf, 320);
+	mutex_unlock(&ctx->kdamond_lock);
+	if (len < 0)
+		return len;
+
+	return simple_read_from_buffer(buf, count, ppos, pids_buf, len);
+}
+
+/*
+ * Converts a string into an array of unsigned long integers
+ *
+ * Returns an array of unsigned long integers if the conversion success, or
+ * NULL otherwise.
+ */
+static int *str_to_pids(const char *str, ssize_t len, ssize_t *nr_pids)
+{
+	int *pids;
+	const int max_nr_pids = 32;
+	int pid;
+	int pos = 0, parsed, ret;
+
+	*nr_pids = 0;
+	pids = kmalloc_array(max_nr_pids, sizeof(pid), GFP_KERNEL);
+	if (!pids)
+		return NULL;
+	while (*nr_pids < max_nr_pids && pos < len) {
+		ret = sscanf(&str[pos], "%d%n", &pid, &parsed);
+		pos += parsed;
+		if (ret != 1)
+			break;
+		pids[*nr_pids] = pid;
+		*nr_pids += 1;
+	}
+	if (*nr_pids == 0) {
+		kfree(pids);
+		pids = NULL;
+	}
+
+	return pids;
+}
+
+static ssize_t debugfs_pids_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	int *targets;
+	ssize_t nr_targets;
+	ssize_t ret = count;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	targets = str_to_pids(kbuf, ret, &nr_targets);
+	if (!targets) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EINVAL;
+		goto unlock_out;
+	}
+
+	err = damon_set_pids(ctx, targets, nr_targets);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+	kfree(targets);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static ssize_t debugfs_record_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char record_buf[20 + MAX_RFILE_PATH_LEN];
+	int ret;
+
+	mutex_lock(&ctx->kdamond_lock);
+	ret = snprintf(record_buf, ARRAY_SIZE(record_buf), "%u %s\n",
+			ctx->rbuf_len, ctx->rfile_path);
+	mutex_unlock(&ctx->kdamond_lock);
+	return simple_read_from_buffer(buf, count, ppos, record_buf, ret);
+}
+
+static ssize_t debugfs_record_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *kbuf;
+	unsigned int rbuf_len;
+	char rfile_path[MAX_RFILE_PATH_LEN];
+	ssize_t ret = count;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	if (sscanf(kbuf, "%u %s",
+				&rbuf_len, rfile_path) != 2) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_recording(ctx, rbuf_len, rfile_path);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static ssize_t debugfs_attrs_read(struct file *file,
+		char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char kbuf[128];
+	int ret;
+
+	mutex_lock(&ctx->kdamond_lock);
+	ret = snprintf(kbuf, ARRAY_SIZE(kbuf), "%lu %lu %lu %lu %lu\n",
+			ctx->sample_interval, ctx->aggr_interval,
+			ctx->regions_update_interval, ctx->min_nr_regions,
+			ctx->max_nr_regions);
+	mutex_unlock(&ctx->kdamond_lock);
+
+	return simple_read_from_buffer(buf, count, ppos, kbuf, ret);
+}
+
+static ssize_t debugfs_attrs_write(struct file *file,
+		const char __user *buf, size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	unsigned long s, a, r, minr, maxr;
+	char *kbuf;
+	ssize_t ret = count;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	if (sscanf(kbuf, "%lu %lu %lu %lu %lu",
+				&s, &a, &r, &minr, &maxr) != 5) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_attrs(ctx, s, a, r, minr, maxr);
+	if (err)
+		ret = err;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
+static const struct file_operations monitor_on_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_monitor_on_read,
+	.write = debugfs_monitor_on_write,
+};
+
+static const struct file_operations pids_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_pids_read,
+	.write = debugfs_pids_write,
+};
+
+static const struct file_operations record_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_record_read,
+	.write = debugfs_record_write,
+};
+
+static const struct file_operations attrs_fops = {
+	.owner = THIS_MODULE,
+	.read = debugfs_attrs_read,
+	.write = debugfs_attrs_write,
+};
+
+static struct dentry *debugfs_root;
+
+static int __init damon_debugfs_init(void)
+{
+	const char * const file_names[] = {"attrs", "record",
+		"pids", "monitor_on"};
+	const struct file_operations *fops[] = {&attrs_fops, &record_fops,
+		&pids_fops, &monitor_on_fops};
+	int i;
+
+	debugfs_root = debugfs_create_dir("damon", NULL);
+	if (!debugfs_root) {
+		pr_err("failed to create the debugfs dir\n");
+		return -ENOMEM;
+	}
+
+	for (i = 0; i < ARRAY_SIZE(file_names); i++) {
+		if (!debugfs_create_file(file_names[i], 0600, debugfs_root,
+					NULL, fops[i])) {
+			pr_err("failed to create %s file\n", file_names[i]);
+			return -ENOMEM;
+		}
+	}
+
+	return 0;
+}
+
+static int __init damon_init_user_ctx(void)
+{
+	int rc;
+
+	struct damon_ctx *ctx = &damon_user_ctx;
+
+	ktime_get_coarse_ts64(&ctx->last_aggregation);
+	ctx->last_regions_update = ctx->last_aggregation;
+
+	rc = damon_set_recording(ctx, 1024 * 1024, "/damon.data");
+	if (rc)
+		return rc;
+
+	mutex_init(&ctx->kdamond_lock);
+
+	INIT_LIST_HEAD(&ctx->tasks_list);
+
+	return 0;
+}
+
 /*
  * Functions for the module loading/unloading
  */
 
 static int __init damon_init(void)
 {
-	return 0;
+	int rc;
+
+	rc = damon_init_user_ctx();
+	if (rc)
+		return rc;
+
+	rc = damon_debugfs_init();
+	if (rc)
+		pr_err("%s: debugfs init failed\n", __func__);
+
+	return rc;
 }
 
 static void __exit damon_exit(void)
 {
+	damon_stop(&damon_user_ctx);
+	debugfs_remove_recursive(debugfs_root);
+
+	kfree(damon_user_ctx.rbuf);
+	kfree(damon_user_ctx.rfile_path);
 }
 
 module_init(damon_init);
-- 
2.17.1

[PATCH v17 10/15] tools: Introduce a minimal user-space tool for DAMON

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit imtroduces a shallow wrapper python script,
``/tools/damon/damo`` that provides more convenient interface.  Note
that it is only aimed to be used for minimal reference of the DAMON's
debugfs interfaces and for debugging of the DAMON itself.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/damon/.gitignore    |   1 +
 tools/damon/_damon.py     | 129 ++++++++++++++
 tools/damon/_dist.py      |  36 ++++
 tools/damon/_recfile.py   |  23 +++
 tools/damon/bin2txt.py    |  67 +++++++
 tools/damon/damo          |  37 ++++
 tools/damon/heats.py      | 362 ++++++++++++++++++++++++++++++++++++++
 tools/damon/nr_regions.py |  91 ++++++++++
 tools/damon/record.py     | 106 +++++++++++
 tools/damon/report.py     |  45 +++++
 tools/damon/wss.py        |  97 ++++++++++
 11 files changed, 994 insertions(+)
 create mode 100644 tools/damon/.gitignore
 create mode 100644 tools/damon/_damon.py
 create mode 100644 tools/damon/_dist.py
 create mode 100644 tools/damon/_recfile.py
 create mode 100644 tools/damon/bin2txt.py
 create mode 100755 tools/damon/damo
 create mode 100644 tools/damon/heats.py
 create mode 100644 tools/damon/nr_regions.py
 create mode 100644 tools/damon/record.py
 create mode 100644 tools/damon/report.py
 create mode 100644 tools/damon/wss.py

diff --git a/tools/damon/.gitignore b/tools/damon/.gitignore
new file mode 100644
index 000000000000..96403d36ff93
--- /dev/null
+++ b/tools/damon/.gitignore
@@ -0,0 +1 @@
+__pycache__/*
diff --git a/tools/damon/_damon.py b/tools/damon/_damon.py
new file mode 100644
index 000000000000..2a08468ad27e
--- /dev/null
+++ b/tools/damon/_damon.py
@@ -0,0 +1,129 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Contains core functions for DAMON debugfs control.
+"""
+
+import os
+import subprocess
+
+debugfs_attrs = None
+debugfs_record = None
+debugfs_pids = None
+debugfs_monitor_on = None
+
+def set_target_pid(pid):
+    return subprocess.call('echo %s > %s' % (pid, debugfs_pids), shell=True,
+            executable='/bin/bash')
+
+def turn_damon(on_off):
+    return subprocess.call("echo %s > %s" % (on_off, debugfs_monitor_on),
+            shell=True, executable="/bin/bash")
+
+def is_damon_running():
+    with open(debugfs_monitor_on, 'r') as f:
+        return f.read().strip() == 'on'
+
+class Attrs:
+    sample_interval = None
+    aggr_interval = None
+    regions_update_interval = None
+    min_nr_regions = None
+    max_nr_regions = None
+    rbuf_len = None
+    rfile_path = None
+
+    def __init__(self, s, a, r, n, x, l, f):
+        self.sample_interval = s
+        self.aggr_interval = a
+        self.regions_update_interval = r
+        self.min_nr_regions = n
+        self.max_nr_regions = x
+        self.rbuf_len = l
+        self.rfile_path = f
+
+    def __str__(self):
+        return "%s %s %s %s %s %s %s" % (self.sample_interval,
+                self.aggr_interval, self.regions_update_interval,
+                self.min_nr_regions, self.max_nr_regions, self.rbuf_len,
+                self.rfile_path)
+
+    def attr_str(self):
+        return "%s %s %s %s %s " % (self.sample_interval, self.aggr_interval,
+                self.regions_update_interval, self.min_nr_regions,
+                self.max_nr_regions)
+
+    def record_str(self):
+        return '%s %s ' % (self.rbuf_len, self.rfile_path)
+
+    def apply(self):
+        ret = subprocess.call('echo %s > %s' % (self.attr_str(), debugfs_attrs),
+                shell=True, executable='/bin/bash')
+        if ret:
+            return ret
+        ret = subprocess.call('echo %s > %s' % (self.record_str(),
+            debugfs_record), shell=True, executable='/bin/bash')
+        if ret:
+            return ret
+
+def current_attrs():
+    with open(debugfs_attrs, 'r') as f:
+        attrs = f.read().split()
+    attrs = [int(x) for x in attrs]
+
+    with open(debugfs_record, 'r') as f:
+        rattrs = f.read().split()
+    attrs.append(int(rattrs[0]))
+    attrs.append(rattrs[1])
+
+    return Attrs(*attrs)
+
+def chk_update_debugfs(debugfs):
+    global debugfs_attrs
+    global debugfs_record
+    global debugfs_pids
+    global debugfs_monitor_on
+
+    debugfs_damon = os.path.join(debugfs, 'damon')
+    debugfs_attrs = os.path.join(debugfs_damon, 'attrs')
+    debugfs_record = os.path.join(debugfs_damon, 'record')
+    debugfs_pids = os.path.join(debugfs_damon, 'pids')
+    debugfs_monitor_on = os.path.join(debugfs_damon, 'monitor_on')
+
+    if not os.path.isdir(debugfs_damon):
+        print("damon debugfs dir (%s) not found", debugfs_damon)
+        exit(1)
+
+    for f in [debugfs_attrs, debugfs_record, debugfs_pids, debugfs_monitor_on]:
+        if not os.path.isfile(f):
+            print("damon debugfs file (%s) not found" % f)
+            exit(1)
+
+def cmd_args_to_attrs(args):
+    "Generate attributes with specified arguments"
+    sample_interval = args.sample
+    aggr_interval = args.aggr
+    regions_update_interval = args.updr
+    min_nr_regions = args.minr
+    max_nr_regions = args.maxr
+    rbuf_len = args.rbuf
+    if not os.path.isabs(args.out):
+        args.out = os.path.join(os.getcwd(), args.out)
+    rfile_path = args.out
+    return Attrs(sample_interval, aggr_interval, regions_update_interval,
+            min_nr_regions, max_nr_regions, rbuf_len, rfile_path)
+
+def set_attrs_argparser(parser):
+    parser.add_argument('-d', '--debugfs', metavar='<debugfs>', type=str,
+            default='/sys/kernel/debug', help='debugfs mounted path')
+    parser.add_argument('-s', '--sample', metavar='<interval>', type=int,
+            default=5000, help='sampling interval')
+    parser.add_argument('-a', '--aggr', metavar='<interval>', type=int,
+            default=100000, help='aggregate interval')
+    parser.add_argument('-u', '--updr', metavar='<interval>', type=int,
+            default=1000000, help='regions update interval')
+    parser.add_argument('-n', '--minr', metavar='<# regions>', type=int,
+            default=10, help='minimal number of regions')
+    parser.add_argument('-m', '--maxr', metavar='<# regions>', type=int,
+            default=1000, help='maximum number of regions')
diff --git a/tools/damon/_dist.py b/tools/damon/_dist.py
new file mode 100644
index 000000000000..9851ec964e5c
--- /dev/null
+++ b/tools/damon/_dist.py
@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import os
+import struct
+import subprocess
+
+def access_patterns(f):
+    nr_regions = struct.unpack('I', f.read(4))[0]
+
+    patterns = []
+    for r in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        eaddr = struct.unpack('L', f.read(8))[0]
+        nr_accesses = struct.unpack('I', f.read(4))[0]
+        patterns.append([eaddr - saddr, nr_accesses])
+    return patterns
+
+def plot_dist(data_file, output_file, xlabel, ylabel):
+    terminal = output_file.split('.')[-1]
+    if not terminal in ['pdf', 'jpeg', 'png', 'svg']:
+        os.remove(data_file)
+        print("Unsupported plot output type.")
+        exit(-1)
+
+    gnuplot_cmd = """
+    set term %s;
+    set output '%s';
+    set key off;
+    set xlabel '%s';
+    set ylabel '%s';
+    plot '%s' with linespoints;""" % (terminal, output_file, xlabel, ylabel,
+            data_file)
+    subprocess.call(['gnuplot', '-e', gnuplot_cmd])
+    os.remove(data_file)
+
diff --git a/tools/damon/_recfile.py b/tools/damon/_recfile.py
new file mode 100644
index 000000000000..331b4d8165d8
--- /dev/null
+++ b/tools/damon/_recfile.py
@@ -0,0 +1,23 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import struct
+
+fmt_version = 0
+
+def set_fmt_version(f):
+    global fmt_version
+
+    mark = f.read(16)
+    if mark == b'damon_recfmt_ver':
+        fmt_version = struct.unpack('i', f.read(4))[0]
+    else:
+        fmt_version = 0
+        f.seek(0)
+    return fmt_version
+
+def pid(f):
+    if fmt_version == 0:
+        return struct.unpack('L', f.read(8))[0]
+    else:
+        return struct.unpack('i', f.read(4))[0]
diff --git a/tools/damon/bin2txt.py b/tools/damon/bin2txt.py
new file mode 100644
index 000000000000..8b9b57a0d727
--- /dev/null
+++ b/tools/damon/bin2txt.py
@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+import os
+import struct
+import sys
+
+import _recfile
+
+def parse_time(bindat):
+    "bindat should be 16 bytes"
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return sec * 1000000000 + nsec;
+
+def pr_region(f):
+    saddr = struct.unpack('L', f.read(8))[0]
+    eaddr = struct.unpack('L', f.read(8))[0]
+    nr_accesses = struct.unpack('I', f.read(4))[0]
+    print("%012x-%012x(%10d):\t%d" %
+            (saddr, eaddr, eaddr - saddr, nr_accesses))
+
+def pr_task_info(f):
+    pid = _recfile.pid(f)
+    print("pid: ", pid)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+    print("nr_regions: ", nr_regions)
+    for r in range(nr_regions):
+        pr_region(f)
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    file_path = args.input
+
+    if not os.path.isfile(file_path):
+        print('input file (%s) is not exist' % file_path)
+        exit(1)
+
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            time = parse_time(timebin)
+            if not start_time:
+                start_time = time
+                print("start_time: ", start_time)
+            print("rel time: %16d" % (time - start_time))
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            print("nr_tasks: ", nr_tasks)
+            for t in range(nr_tasks):
+                pr_task_info(f)
+                print("")
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/damo b/tools/damon/damo
new file mode 100755
index 000000000000..58e1099ae5fc
--- /dev/null
+++ b/tools/damon/damo
@@ -0,0 +1,37 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+
+import record
+import report
+
+class SubCmdHelpFormatter(argparse.RawDescriptionHelpFormatter):
+    def _format_action(self, action):
+        parts = super(argparse.RawDescriptionHelpFormatter,
+                self)._format_action(action)
+        # skip sub parsers help
+        if action.nargs == argparse.PARSER:
+            parts = '\n'.join(parts.split('\n')[1:])
+        return parts
+
+parser = argparse.ArgumentParser(formatter_class=SubCmdHelpFormatter)
+
+subparser = parser.add_subparsers(title='command', dest='command',
+        metavar='<command>')
+subparser.required = True
+
+parser_record = subparser.add_parser('record',
+        help='record data accesses of the given target processes')
+record.set_argparser(parser_record)
+
+parser_report = subparser.add_parser('report',
+        help='report the recorded data accesses in the specified form')
+report.set_argparser(parser_report)
+
+args = parser.parse_args()
+
+if args.command == 'record':
+    record.main(args)
+elif args.command == 'report':
+    report.main(args)
diff --git a/tools/damon/heats.py b/tools/damon/heats.py
new file mode 100644
index 000000000000..99837083874e
--- /dev/null
+++ b/tools/damon/heats.py
@@ -0,0 +1,362 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Transform binary trace data into human readable text that can be used for
+heatmap drawing, or directly plot the data in a heatmap format.
+
+Format of the text is:
+
+    <time> <space> <heat>
+    ...
+
+"""
+
+import argparse
+import os
+import struct
+import subprocess
+import sys
+import tempfile
+
+import _recfile
+
+class HeatSample:
+    space_idx = None
+    sz_time_space = None
+    heat = None
+
+    def __init__(self, space_idx, sz_time_space, heat):
+        if sz_time_space < 0:
+            raise RuntimeError()
+        self.space_idx = space_idx
+        self.sz_time_space = sz_time_space
+        self.heat = heat
+
+    def total_heat(self):
+        return self.heat * self.sz_time_space
+
+    def merge(self, sample):
+        "sample must have a space idx that same to self"
+        heat_sum = self.total_heat() + sample.total_heat()
+        self.heat = heat_sum / (self.sz_time_space + sample.sz_time_space)
+        self.sz_time_space += sample.sz_time_space
+
+def pr_samples(samples, time_idx, time_unit, region_unit):
+    display_time = time_idx * time_unit
+    for idx, sample in enumerate(samples):
+        display_addr = idx * region_unit
+        if not sample:
+            print("%s\t%s\t%s" % (display_time, display_addr, 0.0))
+            continue
+        print("%s\t%s\t%s" % (display_time, display_addr, sample.total_heat() /
+            time_unit / region_unit))
+
+def to_idx(value, min_, unit):
+    return (value - min_) // unit
+
+def read_task_heats(f, pid, aunit, amin, amax):
+    pid_ = _recfile.pid(f)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+    if pid_ != pid:
+        f.read(20 * nr_regions)
+        return None
+    samples = []
+    for i in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        eaddr = struct.unpack('L', f.read(8))[0]
+        eaddr = min(eaddr, amax - 1)
+        heat = struct.unpack('I', f.read(4))[0]
+
+        if eaddr <= amin:
+            continue
+        if saddr >= amax:
+            continue
+        saddr = max(amin, saddr)
+        eaddr = min(amax, eaddr)
+
+        sidx = to_idx(saddr, amin, aunit)
+        eidx = to_idx(eaddr - 1, amin, aunit)
+        for idx in range(sidx, eidx + 1):
+            sa = max(amin + idx * aunit, saddr)
+            ea = min(amin + (idx + 1) * aunit, eaddr)
+            sample = HeatSample(idx, (ea - sa), heat)
+            samples.append(sample)
+    return samples
+
+def parse_time(bindat):
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return sec * 1000000000 + nsec
+
+def apply_samples(target_samples, samples, start_time, end_time, aunit, amin):
+    for s in samples:
+        sample = HeatSample(s.space_idx,
+                s.sz_time_space * (end_time - start_time), s.heat)
+        idx = sample.space_idx
+        if not target_samples[idx]:
+            target_samples[idx] = sample
+        else:
+            target_samples[idx].merge(sample)
+
+def __pr_heats(f, pid, tunit, tmin, tmax, aunit, amin, amax):
+    heat_samples = [None] * ((amax - amin) // aunit)
+
+    start_time = 0
+    end_time = 0
+    last_flushed = -1
+    while True:
+        start_time = end_time
+        timebin = f.read(16)
+        if (len(timebin)) != 16:
+            break
+        end_time = parse_time(timebin)
+        nr_tasks = struct.unpack('I', f.read(4))[0]
+        samples_set = {}
+        for t in range(nr_tasks):
+            samples = read_task_heats(f, pid, aunit, amin, amax)
+            if samples:
+                samples_set[pid] = samples
+        if not pid in samples_set:
+            continue
+        if start_time >= tmax:
+            continue
+        if end_time <= tmin:
+            continue
+        start_time = max(start_time, tmin)
+        end_time = min(end_time, tmax)
+
+        sidx = to_idx(start_time, tmin, tunit)
+        eidx = to_idx(end_time - 1, tmin, tunit)
+        for idx in range(sidx, eidx + 1):
+            if idx != last_flushed:
+                pr_samples(heat_samples, idx, tunit, aunit)
+                heat_samples = [None] * ((amax - amin) // aunit)
+                last_flushed = idx
+            st = max(start_time, tmin + idx * tunit)
+            et = min(end_time, tmin + (idx + 1) * tunit)
+            apply_samples(heat_samples, samples_set[pid], st, et, aunit, amin)
+
+def pr_heats(args):
+    binfile = args.input
+    pid = args.pid
+    tres = args.tres
+    tmin = args.tmin
+    ares = args.ares
+    amin = args.amin
+
+    tunit = (args.tmax - tmin) // tres
+    aunit = (args.amax - amin) // ares
+
+    # Compensate the values so that those fit with the resolution
+    tmax = tmin + tunit * tres
+    amax = amin + aunit * ares
+
+    with open(binfile, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        __pr_heats(f, pid, tunit, tmin, tmax, aunit, amin, amax)
+
+class GuideInfo:
+    pid = None
+    start_time = None
+    end_time = None
+    lowest_addr = None
+    highest_addr = None
+    gaps = None
+
+    def __init__(self, pid, start_time):
+        self.pid = pid
+        self.start_time = start_time
+        self.gaps = []
+
+    def regions(self):
+        regions = []
+        region = [self.lowest_addr]
+        for gap in self.gaps:
+            for idx, point in enumerate(gap):
+                if idx == 0:
+                    region.append(point)
+                    regions.append(region)
+                else:
+                    region = [point]
+        region.append(self.highest_addr)
+        regions.append(region)
+        return regions
+
+    def total_space(self):
+        ret = 0
+        for r in self.regions():
+            ret += r[1] - r[0]
+        return ret
+
+    def __str__(self):
+        lines = ['pid:%d' % self.pid]
+        lines.append('time: %d-%d (%d)' % (self.start_time, self.end_time,
+                    self.end_time - self.start_time))
+        for idx, region in enumerate(self.regions()):
+            lines.append('region\t%2d: %020d-%020d (%d)' %
+                    (idx, region[0], region[1], region[1] - region[0]))
+        return '\n'.join(lines)
+
+def is_overlap(region1, region2):
+    if region1[1] < region2[0]:
+        return False
+    if region2[1] < region1[0]:
+        return False
+    return True
+
+def overlap_region_of(region1, region2):
+    return [max(region1[0], region2[0]), min(region1[1], region2[1])]
+
+def overlapping_regions(regions1, regions2):
+    overlap_regions = []
+    for r1 in regions1:
+        for r2 in regions2:
+            if is_overlap(r1, r2):
+                r1 = overlap_region_of(r1, r2)
+        if r1:
+            overlap_regions.append(r1)
+    return overlap_regions
+
+def get_guide_info(binfile):
+    "Read file, return the set of guide information objects of the data"
+    guides = {}
+    with open(binfile, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            monitor_time = parse_time(timebin)
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                nr_regions = struct.unpack('I', f.read(4))[0]
+                if not pid in guides:
+                    guides[pid] = GuideInfo(pid, monitor_time)
+                guide = guides[pid]
+                guide.end_time = monitor_time
+
+                last_addr = None
+                gaps = []
+                for r in range(nr_regions):
+                    saddr = struct.unpack('L', f.read(8))[0]
+                    eaddr = struct.unpack('L', f.read(8))[0]
+                    f.read(4)
+
+                    if not guide.lowest_addr or saddr < guide.lowest_addr:
+                        guide.lowest_addr = saddr
+                    if not guide.highest_addr or eaddr > guide.highest_addr:
+                        guide.highest_addr = eaddr
+
+                    if not last_addr:
+                        last_addr = eaddr
+                        continue
+                    if last_addr != saddr:
+                        gaps.append([last_addr, saddr])
+                    last_addr = eaddr
+
+                if not guide.gaps:
+                    guide.gaps = gaps
+                else:
+                    guide.gaps = overlapping_regions(guide.gaps, gaps)
+    return sorted(list(guides.values()), key=lambda x: x.total_space(),
+                    reverse=True)
+
+def pr_guide(binfile):
+    for guide in get_guide_info(binfile):
+        print(guide)
+
+def region_sort_key(region):
+    return region[1] - region[0]
+
+def set_missed_args(args):
+    if args.pid and args.tmin and args.tmax and args.amin and args.amax:
+        return
+    guides = get_guide_info(args.input)
+    guide = guides[0]
+    if not args.pid:
+        args.pid = guide.pid
+    for g in guides:
+        if g.pid == args.pid:
+            guide = g
+            break
+
+    if not args.tmin:
+        args.tmin = guide.start_time
+    if not args.tmax:
+        args.tmax = guide.end_time
+
+    if not args.amin or not args.amax:
+        region = sorted(guide.regions(), key=lambda x: x[1] - x[0],
+                reverse=True)[0]
+        args.amin = region[0]
+        args.amax = region[1]
+
+def plot_heatmap(data_file, output_file):
+    terminal = output_file.split('.')[-1]
+    if not terminal in ['pdf', 'jpeg', 'png', 'svg']:
+        os.remove(data_file)
+        print("Unsupported plot output type.")
+        exit(-1)
+
+    gnuplot_cmd = """
+    set term %s;
+    set output '%s';
+    set key off;
+    set xrange [0:];
+    set yrange [0:];
+    set xlabel 'Time (ns)';
+    set ylabel 'Virtual Address (bytes)';
+    plot '%s' using 1:2:3 with image;""" % (terminal, output_file, data_file)
+    subprocess.call(['gnuplot', '-e', gnuplot_cmd])
+    os.remove(data_file)
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--pid', metavar='<pid>', type=int,
+            help='pid of target task')
+    parser.add_argument('--tres', metavar='<resolution>', type=int,
+            default=500, help='time resolution of the output')
+    parser.add_argument('--tmin', metavar='<time>', type=lambda x: int(x,0),
+            help='minimal time of the output')
+    parser.add_argument('--tmax', metavar='<time>', type=lambda x: int(x,0),
+            help='maximum time of the output')
+    parser.add_argument('--ares', metavar='<resolution>', type=int, default=500,
+            help='space address resolution of the output')
+    parser.add_argument('--amin', metavar='<address>', type=lambda x: int(x,0),
+            help='minimal space address of the output')
+    parser.add_argument('--amax', metavar='<address>', type=lambda x: int(x,0),
+            help='maximum space address of the output')
+    parser.add_argument('--guide', action='store_true',
+            help='print a guidance for the min/max/resolution settings')
+    parser.add_argument('--heatmap', metavar='<file>', type=str,
+            help='heatmap image file to create')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    if args.guide:
+        pr_guide(args.input)
+    else:
+        set_missed_args(args)
+        orig_stdout = sys.stdout
+        if args.heatmap:
+            tmp_path = tempfile.mkstemp()[1]
+            tmp_file = open(tmp_path, 'w')
+            sys.stdout = tmp_file
+
+        pr_heats(args)
+
+        if args.heatmap:
+            sys.stdout = orig_stdout
+            tmp_file.flush()
+            tmp_file.close()
+            plot_heatmap(tmp_path, args.heatmap)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/nr_regions.py b/tools/damon/nr_regions.py
new file mode 100644
index 000000000000..655ee50a7b8d
--- /dev/null
+++ b/tools/damon/nr_regions.py
@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Print out distribution of the number of regions in the given record"
+
+import argparse
+import struct
+import sys
+import tempfile
+
+import _dist
+import _recfile
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--range', '-r', type=int, nargs=3,
+            metavar=('<start>', '<stop>', '<step>'),
+            help='range of percentiles to print')
+    parser.add_argument('--sortby', '-s', choices=['time', 'size'],
+            help='the metric to be used for sorting the number of regions')
+    parser.add_argument('--plot', '-p', type=str, metavar='<file>',
+            help='plot the distribution to an image file')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    percentiles = [0, 25, 50, 75, 100]
+
+    file_path = args.input
+    if args.range:
+        percentiles = range(args.range[0], args.range[1], args.range[2])
+    nr_regions_sort = True
+    if args.sortby == 'time':
+        nr_regions_sort = False
+
+    pid_pattern_map = {}
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                if not pid in pid_pattern_map:
+                    pid_pattern_map[pid] = []
+                pid_pattern_map[pid].append(_dist.access_patterns(f))
+
+    orig_stdout = sys.stdout
+    if args.plot:
+        tmp_path = tempfile.mkstemp()[1]
+        tmp_file = open(tmp_path, 'w')
+        sys.stdout = tmp_file
+
+    print('# <percentile> <# regions>')
+    for pid in pid_pattern_map.keys():
+        # Skip firs 20 regions as those would not adaptively adjusted
+        snapshots = pid_pattern_map[pid][20:]
+        nr_regions_dist = []
+        for snapshot in snapshots:
+            nr_regions_dist.append(len(snapshot))
+        if nr_regions_sort:
+            nr_regions_dist.sort(reverse=False)
+
+        print('# pid\t%s' % pid)
+        print('# avr:\t%d' % (sum(nr_regions_dist) / len(nr_regions_dist)))
+        for percentile in percentiles:
+            thres_idx = int(percentile / 100.0 * len(nr_regions_dist))
+            if thres_idx == len(nr_regions_dist):
+                thres_idx -= 1
+            threshold = nr_regions_dist[thres_idx]
+            print('%d\t%d' % (percentile, nr_regions_dist[thres_idx]))
+
+    if args.plot:
+        sys.stdout = orig_stdout
+        tmp_file.flush()
+        tmp_file.close()
+        xlabel = 'runtime (percent)'
+        if nr_regions_sort:
+            xlabel = 'percentile'
+        _dist.plot_dist(tmp_path, args.plot, xlabel,
+                'number of monitoring target regions')
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/record.py b/tools/damon/record.py
new file mode 100644
index 000000000000..44fa3a12af35
--- /dev/null
+++ b/tools/damon/record.py
@@ -0,0 +1,106 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Record data access patterns of the target process.
+"""
+
+import argparse
+import os
+import signal
+import subprocess
+import time
+
+import _damon
+
+def do_record(target, is_target_cmd, attrs, old_attrs):
+    if os.path.isfile(attrs.rfile_path):
+        os.rename(attrs.rfile_path, attrs.rfile_path + '.old')
+
+    if attrs.apply():
+        print('attributes (%s) failed to be applied' % attrs)
+        cleanup_exit(old_attrs, -1)
+    print('# damon attrs: %s %s' % (attrs.attr_str(), attrs.record_str()))
+    if is_target_cmd:
+        p = subprocess.Popen(target, shell=True, executable='/bin/bash')
+        target = p.pid
+    if _damon.set_target_pid(target):
+        print('pid setting (%s) failed' % target)
+        cleanup_exit(old_attrs, -2)
+    if _damon.turn_damon('on'):
+        print('could not turn on damon' % target)
+        cleanup_exit(old_attrs, -3)
+    while not _damon.is_damon_running():
+        time.sleep(1)
+    print('Press Ctrl+C to stop')
+    if is_target_cmd:
+        p.wait()
+    while True:
+        # damon will turn it off by itself if the target tasks are terminated.
+        if not _damon.is_damon_running():
+            break
+        time.sleep(1)
+
+    cleanup_exit(old_attrs, 0)
+
+def cleanup_exit(orig_attrs, exit_code):
+    if _damon.is_damon_running():
+        if _damon.turn_damon('off'):
+            print('failed to turn damon off!')
+        while _damon.is_damon_running():
+            time.sleep(1)
+    if orig_attrs:
+        if orig_attrs.apply():
+            print('original attributes (%s) restoration failed!' % orig_attrs)
+    exit(exit_code)
+
+def sighandler(signum, frame):
+    print('\nsignal %s received' % signum)
+    cleanup_exit(orig_attrs, signum)
+
+def chk_permission():
+    if os.geteuid() != 0:
+        print("Run as root")
+        exit(1)
+
+def set_argparser(parser):
+    _damon.set_attrs_argparser(parser)
+    parser.add_argument('target', type=str, metavar='<target>',
+            help='the target command or the pid to record')
+    parser.add_argument('-l', '--rbuf', metavar='<len>', type=int,
+            default=1024*1024, help='length of record result buffer')
+    parser.add_argument('-o', '--out', metavar='<file path>', type=str,
+            default='damon.data', help='output file path')
+
+def main(args=None):
+    global orig_attrs
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    chk_permission()
+    _damon.chk_update_debugfs(args.debugfs)
+
+    signal.signal(signal.SIGINT, sighandler)
+    signal.signal(signal.SIGTERM, sighandler)
+    orig_attrs = _damon.current_attrs()
+
+    args.schemes = ''
+    new_attrs = _damon.cmd_args_to_attrs(args)
+    target = args.target
+
+    target_fields = target.split()
+    if not subprocess.call('which %s > /dev/null' % target_fields[0],
+            shell=True, executable='/bin/bash'):
+        do_record(target, True, new_attrs, orig_attrs)
+    else:
+        try:
+            pid = int(target)
+        except:
+            print('target \'%s\' is neither a command, nor a pid' % target)
+            exit(1)
+        do_record(target, False, new_attrs, orig_attrs)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/report.py b/tools/damon/report.py
new file mode 100644
index 000000000000..c661c7b2f1af
--- /dev/null
+++ b/tools/damon/report.py
@@ -0,0 +1,45 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+import argparse
+
+import bin2txt
+import heats
+import nr_regions
+import wss
+
+def set_argparser(parser):
+    subparsers = parser.add_subparsers(title='report type', dest='report_type',
+            metavar='<report type>', help='the type of the report to generate')
+    subparsers.required = True
+
+    parser_raw = subparsers.add_parser('raw', help='human readable raw data')
+    bin2txt.set_argparser(parser_raw)
+
+    parser_heats = subparsers.add_parser('heats', help='heats of regions')
+    heats.set_argparser(parser_heats)
+
+    parser_wss = subparsers.add_parser('wss', help='working set size')
+    wss.set_argparser(parser_wss)
+
+    parser_nr_regions = subparsers.add_parser('nr_regions',
+            help='number of regions')
+    nr_regions.set_argparser(parser_nr_regions)
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    if args.report_type == 'raw':
+        bin2txt.main(args)
+    elif args.report_type == 'heats':
+        heats.main(args)
+    elif args.report_type == 'wss':
+        wss.main(args)
+    elif args.report_type == 'nr_regions':
+        nr_regions.main(args)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/wss.py b/tools/damon/wss.py
new file mode 100644
index 000000000000..b43065176cfd
--- /dev/null
+++ b/tools/damon/wss.py
@@ -0,0 +1,97 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Print out the distribution of the working set sizes of the given trace"
+
+import argparse
+import struct
+import sys
+import tempfile
+
+import _dist
+import _recfile
+
+def set_argparser(parser):
+    parser.add_argument('--input', '-i', type=str, metavar='<file>',
+            default='damon.data', help='input file name')
+    parser.add_argument('--range', '-r', type=int, nargs=3,
+            metavar=('<start>', '<stop>', '<step>'),
+            help='range of wss percentiles to print')
+    parser.add_argument('--sortby', '-s', choices=['time', 'size'],
+            help='the metric to be used for the sort of the working set sizes')
+    parser.add_argument('--plot', '-p', type=str, metavar='<file>',
+            help='plot the distribution to an image file')
+
+def main(args=None):
+    if not args:
+        parser = argparse.ArgumentParser()
+        set_argparser(parser)
+        args = parser.parse_args()
+
+    percentiles = [0, 25, 50, 75, 100]
+
+    file_path = args.input
+    if args.range:
+        percentiles = range(args.range[0], args.range[1], args.range[2])
+    wss_sort = True
+    if args.sortby == 'time':
+        wss_sort = False
+
+    pid_pattern_map = {}
+    with open(file_path, 'rb') as f:
+        _recfile.set_fmt_version(f)
+        start_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                pid = _recfile.pid(f)
+                if not pid in pid_pattern_map:
+                    pid_pattern_map[pid] = []
+                pid_pattern_map[pid].append(_dist.access_patterns(f))
+
+    orig_stdout = sys.stdout
+    if args.plot:
+        tmp_path = tempfile.mkstemp()[1]
+        tmp_file = open(tmp_path, 'w')
+        sys.stdout = tmp_file
+
+    print('# <percentile> <wss>')
+    for pid in pid_pattern_map.keys():
+        # Skip first 20 snapshots as regions may not adjusted yet.
+        snapshots = pid_pattern_map[pid][20:]
+        wss_dist = []
+        for snapshot in snapshots:
+            wss = 0
+            for p in snapshot:
+                # Ignore regions not accessed
+                if p[1] <= 0:
+                    continue
+                wss += p[0]
+            wss_dist.append(wss)
+        if wss_sort:
+            wss_dist.sort(reverse=False)
+
+        print('# pid\t%s' % pid)
+        print('# avr:\t%d' % (sum(wss_dist) / len(wss_dist)))
+        for percentile in percentiles:
+            thres_idx = int(percentile / 100.0 * len(wss_dist))
+            if thres_idx == len(wss_dist):
+                thres_idx -= 1
+            threshold = wss_dist[thres_idx]
+            print('%d\t%d' % (percentile, wss_dist[thres_idx]))
+
+    if args.plot:
+        sys.stdout = orig_stdout
+        tmp_file.flush()
+        tmp_file.close()
+        xlabel = 'runtime (percent)'
+        if wss_sort:
+            xlabel = 'percentile'
+        _dist.plot_dist(tmp_path, args.plot, xlabel,
+                'working set size (bytes)')
+
+if __name__ == '__main__':
+    main()
-- 
2.17.1

[PATCH v17 11/15] tools/damon/wss: Implement '--thres' option

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

Currently, 'wss' treats every region as working set if accessed at least
once.  Someone who want to know performance important working set only
would want to ignore regions having low access frequency.  '--thres'
option can be used to set the minimal access frequency of the regions to
be classified as the workingset.

Using this, users can plot the reuse histogram.  For example:

    $ damo record $(pidof raytrace)
    $ for t in {1..20}; do ./tools/damon/damo report wss --thres $t | \
    		grep avr | awk -v reuse_time=$(( (21 - t) * 5 )) \
    		'{print reuse_time " " $3}'; done
    100 12838416
    95 2222623
    90 1585480
    85 422890
    80 67040
    75 45218
    70 13242
    65 12896
    60 12136
    55 10872
    50 9648
    45 8136
    40 7052
    35 6304
    30 5736
    25 5404
    20 5305
    15 5187
    10 5069
    5 4873

Above command shows the reuse histogram of parsec3.raytrace.  Remind
that the sampling interval and aggregation interval are 5ms and 100ms
by default and this command used the default values.  So, the above
output means that about 12MB of memory region was reused within 100 ms
while only about 2MB of memory region was reused within 95 ms, then
about 1.5MB within 90ms, and so on, in average.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/damon/wss.py | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/tools/damon/wss.py b/tools/damon/wss.py
index b43065176cfd..d2a1b149e3ea 100644
--- a/tools/damon/wss.py
+++ b/tools/damon/wss.py
@@ -17,6 +17,8 @@ def set_argparser(parser):
     parser.add_argument('--range', '-r', type=int, nargs=3,
             metavar=('<start>', '<stop>', '<step>'),
             help='range of wss percentiles to print')
+    parser.add_argument('--thres', '-t', type=int, metavar='<# accesses>',
+            help='minimal number of accesses for treated as working set')
     parser.add_argument('--sortby', '-s', choices=['time', 'size'],
             help='the metric to be used for the sort of the working set sizes')
     parser.add_argument('--plot', '-p', type=str, metavar='<file>',
@@ -67,7 +69,7 @@ def main(args=None):
             wss = 0
             for p in snapshot:
                 # Ignore regions not accessed
-                if p[1] <= 0:
+                if p[1] < args.thres:
                     continue
                 wss += p[0]
             wss_dist.append(wss)
-- 
2.17.1

[PATCH v17 13/15] mm/damon: Add kunit tests

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds kunit based unit tests for DAMON.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
Reviewed-by: Brendan Higgins <brendanhiggins@google.com>
---
 mm/Kconfig      |  11 +
 mm/damon-test.h | 661 ++++++++++++++++++++++++++++++++++++++++++++++++
 mm/damon.c      |   6 +
 3 files changed, 678 insertions(+)
 create mode 100644 mm/damon-test.h

diff --git a/mm/Kconfig b/mm/Kconfig
index 464e9594dcec..e32761985611 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -879,4 +879,15 @@ config DAMON
 	  more information.
 	  If unsure, say N.
 
+config DAMON_KUNIT_TEST
+	bool "Test for damon"
+	depends on DAMON=y && KUNIT
+	help
+	  This builds the DAMON Kunit test suite.
+
+	  For more information on KUnit and unit tests in general, please refer
+	  to the KUnit documentation.
+
+	  If unsure, say N.
+
 endmenu
diff --git a/mm/damon-test.h b/mm/damon-test.h
new file mode 100644
index 000000000000..b31c7fe913ca
--- /dev/null
+++ b/mm/damon-test.h
@@ -0,0 +1,661 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Data Access Monitor Unit Tests
+ *
+ * Copyright 2019 Amazon.com, Inc. or its affiliates.  All rights reserved.
+ *
+ * Author: SeongJae Park <sjpark@amazon.de>
+ */
+
+#ifdef CONFIG_DAMON_KUNIT_TEST
+
+#ifndef _DAMON_TEST_H
+#define _DAMON_TEST_H
+
+#include <kunit/test.h>
+
+static void damon_test_str_to_pids(struct kunit *test)
+{
+	char *question;
+	int *answers;
+	int expected[] = {12, 35, 46};
+	ssize_t nr_integers = 0, i;
+
+	question = "123";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+	KUNIT_EXPECT_EQ(test, 123, answers[0]);
+	kfree(answers);
+
+	question = "123abc";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)1, nr_integers);
+	KUNIT_EXPECT_EQ(test, 123, answers[0]);
+	kfree(answers);
+
+	question = "a123";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, answers, (int *)NULL);
+
+	question = "12 35";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+	for (i = 0; i < nr_integers; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "12 35 46";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)3, nr_integers);
+	for (i = 0; i < nr_integers; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "12 35 abc 46";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)2, nr_integers);
+	for (i = 0; i < 2; i++)
+		KUNIT_EXPECT_EQ(test, expected[i], answers[i]);
+	kfree(answers);
+
+	question = "";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, (int *)NULL, answers);
+	kfree(answers);
+
+	question = "\n";
+	answers = str_to_pids(question, strnlen(question, 128), &nr_integers);
+	KUNIT_EXPECT_EQ(test, (ssize_t)0, nr_integers);
+	KUNIT_EXPECT_PTR_EQ(test, (int *)NULL, answers);
+	kfree(answers);
+}
+
+static void damon_test_regions(struct kunit *test)
+{
+	struct damon_region *r;
+	struct damon_task *t;
+
+	r = damon_new_region(1, 2);
+	KUNIT_EXPECT_EQ(test, 1ul, r->ar.start);
+	KUNIT_EXPECT_EQ(test, 2ul, r->ar.end);
+	KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+
+	t = damon_new_task(42);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_regions(t));
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, 1u, nr_damon_regions(t));
+
+	damon_del_region(r);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_regions(t));
+
+	damon_free_task(t);
+}
+
+static void damon_test_tasks(struct kunit *test)
+{
+	struct damon_ctx *c = &damon_user_ctx;
+	struct damon_task *t;
+
+	t = damon_new_task(42);
+	KUNIT_EXPECT_EQ(test, 42, t->pid);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_tasks(c));
+
+	damon_add_task(&damon_user_ctx, t);
+	KUNIT_EXPECT_EQ(test, 1u, nr_damon_tasks(c));
+
+	damon_destroy_task(t);
+	KUNIT_EXPECT_EQ(test, 0u, nr_damon_tasks(c));
+}
+
+static void damon_test_set_pids(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	int pids[] = {1, 2, 3};
+	char buf[64];
+
+	damon_set_pids(ctx, pids, 3);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2 3\n");
+
+	damon_set_pids(ctx, NULL, 0);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+
+	damon_set_pids(ctx, (int []){1, 2}, 2);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "1 2\n");
+
+	damon_set_pids(ctx, (int []){2}, 1);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "2\n");
+
+	damon_set_pids(ctx, NULL, 0);
+	damon_sprint_pids(ctx, buf, 64);
+	KUNIT_EXPECT_STREQ(test, (char *)buf, "\n");
+}
+
+static void damon_test_set_recording(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	int err;
+
+	err = damon_set_recording(ctx, 42, "foo");
+	KUNIT_EXPECT_EQ(test, err, -EINVAL);
+	damon_set_recording(ctx, 4242, "foo.bar");
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_len, 4242u);
+	KUNIT_EXPECT_STREQ(test, ctx->rfile_path, "foo.bar");
+	damon_set_recording(ctx, 424242, "foo");
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_len, 424242u);
+	KUNIT_EXPECT_STREQ(test, ctx->rfile_path, "foo");
+}
+
+static void __link_vmas(struct vm_area_struct *vmas, ssize_t nr_vmas)
+{
+	int i, j;
+	unsigned long largest_gap, gap;
+
+	if (!nr_vmas)
+		return;
+
+	for (i = 0; i < nr_vmas - 1; i++) {
+		vmas[i].vm_next = &vmas[i + 1];
+
+		vmas[i].vm_rb.rb_left = NULL;
+		vmas[i].vm_rb.rb_right = &vmas[i + 1].vm_rb;
+
+		largest_gap = 0;
+		for (j = i; j < nr_vmas; j++) {
+			if (j == 0)
+				continue;
+			gap = vmas[j].vm_start - vmas[j - 1].vm_end;
+			if (gap > largest_gap)
+				largest_gap = gap;
+		}
+		vmas[i].rb_subtree_gap = largest_gap;
+	}
+	vmas[i].vm_next = NULL;
+	vmas[i].vm_rb.rb_right = NULL;
+	vmas[i].rb_subtree_gap = 0;
+}
+
+/*
+ * Test damon_three_regions_in_vmas() function
+ *
+ * DAMON converts the complex and dynamic memory mappings of each target task
+ * to three discontiguous regions which cover every mapped areas.  However, the
+ * three regions should not include the two biggest unmapped areas in the
+ * original mapping, because the two biggest areas are normally the areas
+ * between 1) heap and the mmap()-ed regions, and 2) the mmap()-ed regions and
+ * stack.  Because these two unmapped areas are very huge but obviously never
+ * accessed, covering the region is just a waste.
+ *
+ * 'damon_three_regions_in_vmas() receives an address space of a process.  It
+ * first identifies the start of mappings, end of mappings, and the two biggest
+ * unmapped areas.  After that, based on the information, it constructs the
+ * three regions and returns.  For more detail, refer to the comment of
+ * 'damon_init_regions_of()' function definition in 'mm/damon.c' file.
+ *
+ * For example, suppose virtual address ranges of 10-20, 20-25, 200-210,
+ * 210-220, 300-305, and 307-330 (Other comments represent this mappings in
+ * more short form: 10-20-25, 200-210-220, 300-305, 307-330) of a process are
+ * mapped.  To cover every mappings, the three regions should start with 10,
+ * and end with 305.  The process also has three unmapped areas, 25-200,
+ * 220-300, and 305-307.  Among those, 25-200 and 220-300 are the biggest two
+ * unmapped areas, and thus it should be converted to three regions of 10-25,
+ * 200-220, and 300-330.
+ */
+static void damon_test_three_regions_in_vmas(struct kunit *test)
+{
+	struct damon_addr_range regions[3] = {0,};
+	/* 10-20-25, 200-210-220, 300-305, 307-330 */
+	struct vm_area_struct vmas[] = {
+		(struct vm_area_struct) {.vm_start = 10, .vm_end = 20},
+		(struct vm_area_struct) {.vm_start = 20, .vm_end = 25},
+		(struct vm_area_struct) {.vm_start = 200, .vm_end = 210},
+		(struct vm_area_struct) {.vm_start = 210, .vm_end = 220},
+		(struct vm_area_struct) {.vm_start = 300, .vm_end = 305},
+		(struct vm_area_struct) {.vm_start = 307, .vm_end = 330},
+	};
+
+	__link_vmas(vmas, 6);
+
+	damon_three_regions_in_vmas(&vmas[0], regions);
+
+	KUNIT_EXPECT_EQ(test, 10ul, regions[0].start);
+	KUNIT_EXPECT_EQ(test, 25ul, regions[0].end);
+	KUNIT_EXPECT_EQ(test, 200ul, regions[1].start);
+	KUNIT_EXPECT_EQ(test, 220ul, regions[1].end);
+	KUNIT_EXPECT_EQ(test, 300ul, regions[2].start);
+	KUNIT_EXPECT_EQ(test, 330ul, regions[2].end);
+}
+
+/* Clean up global state of damon */
+static void damon_cleanup_global_state(void)
+{
+	struct damon_task *t, *next;
+
+	damon_for_each_task_safe(t, next, &damon_user_ctx)
+		damon_destroy_task(t);
+
+	damon_user_ctx.rbuf_offset = 0;
+}
+
+/*
+ * Test kdamond_reset_aggregated()
+ *
+ * DAMON checks access to each region and aggregates this information as the
+ * access frequency of each region.  In detail, it increases '->nr_accesses' of
+ * regions that an access has confirmed.  'kdamond_reset_aggregated()' flushes
+ * the aggregated information ('->nr_accesses' of each regions) to the result
+ * buffer.  As a result of the flushing, the '->nr_accesses' of regions are
+ * initialized to zero.
+ */
+static void damon_test_aggregate(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	int pids[] = {1, 2, 3};
+	unsigned long saddr[][3] = {{10, 20, 30}, {5, 42, 49}, {13, 33, 55} };
+	unsigned long eaddr[][3] = {{15, 27, 40}, {31, 45, 55}, {23, 44, 66} };
+	unsigned long accesses[][3] = {{42, 95, 84}, {10, 20, 30}, {0, 1, 2} };
+	struct damon_task *t;
+	struct damon_region *r;
+	int it, ir;
+	ssize_t sz, sr, sp;
+
+	damon_set_recording(ctx, 4242, "damon.data");
+	damon_set_pids(ctx, pids, 3);
+
+	it = 0;
+	damon_for_each_task(t, ctx) {
+		for (ir = 0; ir < 3; ir++) {
+			r = damon_new_region(saddr[it][ir], eaddr[it][ir]);
+			r->nr_accesses = accesses[it][ir];
+			damon_add_region(r, t);
+		}
+		it++;
+	}
+	kdamond_reset_aggregated(ctx);
+	it = 0;
+	damon_for_each_task(t, ctx) {
+		ir = 0;
+		/* '->nr_accesses' should be zeroed */
+		damon_for_each_region(r, t) {
+			KUNIT_EXPECT_EQ(test, 0u, r->nr_accesses);
+			ir++;
+		}
+		/* regions should be preserved */
+		KUNIT_EXPECT_EQ(test, 3, ir);
+		it++;
+	}
+	/* tasks also should be preserved */
+	KUNIT_EXPECT_EQ(test, 3, it);
+
+	/* The aggregated information should be written in the buffer */
+	sr = sizeof(r->ar.start) + sizeof(r->ar.end) + sizeof(r->nr_accesses);
+	sp = sizeof(t->pid) + sizeof(unsigned int) + 3 * sr;
+	sz = sizeof(struct timespec64) + sizeof(unsigned int) + 3 * sp;
+	KUNIT_EXPECT_EQ(test, (unsigned int)sz, ctx->rbuf_offset);
+
+	damon_set_recording(ctx, 0, "damon.data");
+	damon_cleanup_global_state();
+}
+
+static void damon_test_write_rbuf(struct kunit *test)
+{
+	struct damon_ctx *ctx = &damon_user_ctx;
+	char *data;
+
+	damon_set_recording(&damon_user_ctx, 4242, "damon.data");
+
+	data = "hello";
+	damon_write_rbuf(ctx, data, strnlen(data, 256));
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_offset, 5u);
+
+	damon_write_rbuf(ctx, data, 0);
+	KUNIT_EXPECT_EQ(test, ctx->rbuf_offset, 5u);
+
+	KUNIT_EXPECT_STREQ(test, (char *)ctx->rbuf, data);
+	damon_set_recording(&damon_user_ctx, 0, "damon.data");
+}
+
+static struct damon_region *__nth_region_of(struct damon_task *t, int idx)
+{
+	struct damon_region *r;
+	unsigned int i = 0;
+
+	damon_for_each_region(r, t) {
+		if (i++ == idx)
+			return r;
+	}
+
+	return NULL;
+}
+
+/*
+ * Test 'damon_apply_three_regions()'
+ *
+ * test			kunit object
+ * regions		an array containing start/end addresses of current
+ *			monitoring target regions
+ * nr_regions		the number of the addresses in 'regions'
+ * three_regions	The three regions that need to be applied now
+ * expected		start/end addresses of monitoring target regions that
+ *			'three_regions' are applied
+ * nr_expected		the number of addresses in 'expected'
+ *
+ * The memory mapping of the target processes changes dynamically.  To follow
+ * the change, DAMON periodically reads the mappings, simplifies it to the
+ * three regions, and updates the monitoring target regions to fit in the three
+ * regions.  The update of current target regions is the role of
+ * 'damon_apply_three_regions()'.
+ *
+ * This test passes the given target regions and the new three regions that
+ * need to be applied to the function and check whether it updates the regions
+ * as expected.
+ */
+static void damon_do_test_apply_three_regions(struct kunit *test,
+				unsigned long *regions, int nr_regions,
+				struct damon_addr_range *three_regions,
+				unsigned long *expected, int nr_expected)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+	int i;
+
+	t = damon_new_task(42);
+	for (i = 0; i < nr_regions / 2; i++) {
+		r = damon_new_region(regions[i * 2], regions[i * 2 + 1]);
+		damon_add_region(r, t);
+	}
+	damon_add_task(&damon_user_ctx, t);
+
+	damon_apply_three_regions(&damon_user_ctx, t, three_regions);
+
+	for (i = 0; i < nr_expected / 2; i++) {
+		r = __nth_region_of(t, i);
+		KUNIT_EXPECT_EQ(test, r->ar.start, expected[i * 2]);
+		KUNIT_EXPECT_EQ(test, r->ar.end, expected[i * 2 + 1]);
+	}
+
+	damon_cleanup_global_state();
+}
+
+/*
+ * This function test most common case where the three big regions are only
+ * slightly changed.  Target regions should adjust their boundary (10-20-30,
+ * 50-55, 70-80, 90-100) to fit with the new big regions or remove target
+ * regions (57-79) that now out of the three regions.
+ */
+static void damon_test_apply_three_regions1(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 45-55, 73-104 */
+	struct damon_addr_range new_three_regions[3] = {
+		(struct damon_addr_range){.start = 5, .end = 27},
+		(struct damon_addr_range){.start = 45, .end = 55},
+		(struct damon_addr_range){.start = 73, .end = 104} };
+	/* 5-20-27, 45-55, 73-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 45, 55,
+				73, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test slightly bigger change.  Similar to above, but the second big region
+ * now require two target regions (50-55, 57-59) to be removed.
+ */
+static void damon_test_apply_three_regions2(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 56-57, 65-104 */
+	struct damon_addr_range new_three_regions[3] = {
+		(struct damon_addr_range){.start = 5, .end = 27},
+		(struct damon_addr_range){.start = 56, .end = 57},
+		(struct damon_addr_range){.start = 65, .end = 104} };
+	/* 5-20-27, 56-57, 65-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 56, 57,
+				65, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test a big change.  The second big region has totally freed and mapped to
+ * different area (50-59 -> 61-63).  The target regions which were in the old
+ * second big region (50-55-57-59) should be removed and new target region
+ * covering the second big region (61-63) should be created.
+ */
+static void damon_test_apply_three_regions3(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-27, 61-63, 65-104 */
+	struct damon_addr_range new_three_regions[3] = {
+		(struct damon_addr_range){.start = 5, .end = 27},
+		(struct damon_addr_range){.start = 61, .end = 63},
+		(struct damon_addr_range){.start = 65, .end = 104} };
+	/* 5-20-27, 61-63, 65-80-90-104 */
+	unsigned long expected[] = {5, 20, 20, 27, 61, 63,
+				65, 80, 80, 90, 90, 104};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+/*
+ * Test another big change.  Both of the second and third big regions (50-59
+ * and 70-100) has totally freed and mapped to different area (30-32 and
+ * 65-68).  The target regions which were in the old second and third big
+ * regions should now be removed and new target regions covering the new second
+ * and third big regions should be crated.
+ */
+static void damon_test_apply_three_regions4(struct kunit *test)
+{
+	/* 10-20-30, 50-55-57-59, 70-80-90-100 */
+	unsigned long regions[] = {10, 20, 20, 30, 50, 55, 55, 57, 57, 59,
+				70, 80, 80, 90, 90, 100};
+	/* 5-7, 30-32, 65-68 */
+	struct damon_addr_range new_three_regions[3] = {
+		(struct damon_addr_range){.start = 5, .end = 7},
+		(struct damon_addr_range){.start = 30, .end = 32},
+		(struct damon_addr_range){.start = 65, .end = 68} };
+	/* expect 5-7, 30-32, 65-68 */
+	unsigned long expected[] = {5, 7, 30, 32, 65, 68};
+
+	damon_do_test_apply_three_regions(test, regions, ARRAY_SIZE(regions),
+			new_three_regions, expected, ARRAY_SIZE(expected));
+}
+
+static void damon_test_split_evenly(struct kunit *test)
+{
+	struct damon_ctx *c = &damon_user_ctx;
+	struct damon_task *t;
+	struct damon_region *r;
+	unsigned long i;
+
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, NULL, 5), -EINVAL);
+
+	t = damon_new_task(42);
+	r = damon_new_region(0, 100);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 0), -EINVAL);
+
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 10), 0);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 10u);
+
+	i = 0;
+	damon_for_each_region(r, t) {
+		KUNIT_EXPECT_EQ(test, r->ar.start, i++ * 10);
+		KUNIT_EXPECT_EQ(test, r->ar.end, i * 10);
+	}
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(5, 59);
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 5), 0);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 5u);
+
+	i = 0;
+	damon_for_each_region(r, t) {
+		if (i == 4)
+			break;
+		KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i++);
+		KUNIT_EXPECT_EQ(test, r->ar.end, 5 + 10 * i);
+	}
+	KUNIT_EXPECT_EQ(test, r->ar.start, 5 + 10 * i);
+	KUNIT_EXPECT_EQ(test, r->ar.end, 59ul);
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(5, 6);
+	damon_add_region(r, t);
+	KUNIT_EXPECT_EQ(test, damon_split_region_evenly(c, r, 2), -EINVAL);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 1u);
+
+	damon_for_each_region(r, t) {
+		KUNIT_EXPECT_EQ(test, r->ar.start, 5ul);
+		KUNIT_EXPECT_EQ(test, r->ar.end, 6ul);
+	}
+	damon_free_task(t);
+}
+
+static void damon_test_split_at(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	t = damon_new_task(42);
+	r = damon_new_region(0, 100);
+	damon_add_region(r, t);
+	damon_split_region_at(&damon_user_ctx, r, 25);
+	KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
+	KUNIT_EXPECT_EQ(test, r->ar.end, 25ul);
+
+	r = damon_next_region(r);
+	KUNIT_EXPECT_EQ(test, r->ar.start, 25ul);
+	KUNIT_EXPECT_EQ(test, r->ar.end, 100ul);
+
+	damon_free_task(t);
+}
+
+static void damon_test_merge_two(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r, *r2, *r3;
+	int i;
+
+	t = damon_new_task(42);
+	r = damon_new_region(0, 100);
+	r->nr_accesses = 10;
+	damon_add_region(r, t);
+	r2 = damon_new_region(100, 300);
+	r2->nr_accesses = 20;
+	damon_add_region(r2, t);
+
+	damon_merge_two_regions(r, r2);
+	KUNIT_EXPECT_EQ(test, r->ar.start, 0ul);
+	KUNIT_EXPECT_EQ(test, r->ar.end, 300ul);
+	KUNIT_EXPECT_EQ(test, r->nr_accesses, 16u);
+
+	i = 0;
+	damon_for_each_region(r3, t) {
+		KUNIT_EXPECT_PTR_EQ(test, r, r3);
+		i++;
+	}
+	KUNIT_EXPECT_EQ(test, i, 1);
+
+	damon_free_task(t);
+}
+
+static void damon_test_merge_regions_of(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+	unsigned long sa[] = {0, 100, 114, 122, 130, 156, 170, 184};
+	unsigned long ea[] = {100, 112, 122, 130, 156, 170, 184, 230};
+	unsigned int nrs[] = {0, 0, 10, 10, 20, 30, 1, 2};
+
+	unsigned long saddrs[] = {0, 114, 130, 156, 170};
+	unsigned long eaddrs[] = {112, 130, 156, 170, 230};
+	int i;
+
+	t = damon_new_task(42);
+	for (i = 0; i < ARRAY_SIZE(sa); i++) {
+		r = damon_new_region(sa[i], ea[i]);
+		r->nr_accesses = nrs[i];
+		damon_add_region(r, t);
+	}
+
+	damon_merge_regions_of(t, 9, 9999);
+	/* 0-112, 114-130, 130-156, 156-170 */
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 5u);
+	for (i = 0; i < 5; i++) {
+		r = __nth_region_of(t, i);
+		KUNIT_EXPECT_EQ(test, r->ar.start, saddrs[i]);
+		KUNIT_EXPECT_EQ(test, r->ar.end, eaddrs[i]);
+	}
+	damon_free_task(t);
+}
+
+static void damon_test_split_regions_of(struct kunit *test)
+{
+	struct damon_task *t;
+	struct damon_region *r;
+
+	t = damon_new_task(42);
+	r = damon_new_region(0, 22);
+	damon_add_region(r, t);
+	damon_split_regions_of(&damon_user_ctx, t, 2);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 2u);
+	damon_free_task(t);
+
+	t = damon_new_task(42);
+	r = damon_new_region(0, 220);
+	damon_add_region(r, t);
+	damon_split_regions_of(&damon_user_ctx, t, 4);
+	KUNIT_EXPECT_EQ(test, nr_damon_regions(t), 4u);
+	damon_free_task(t);
+}
+
+static struct kunit_case damon_test_cases[] = {
+	KUNIT_CASE(damon_test_str_to_pids),
+	KUNIT_CASE(damon_test_tasks),
+	KUNIT_CASE(damon_test_regions),
+	KUNIT_CASE(damon_test_set_pids),
+	KUNIT_CASE(damon_test_set_recording),
+	KUNIT_CASE(damon_test_three_regions_in_vmas),
+	KUNIT_CASE(damon_test_aggregate),
+	KUNIT_CASE(damon_test_write_rbuf),
+	KUNIT_CASE(damon_test_apply_three_regions1),
+	KUNIT_CASE(damon_test_apply_three_regions2),
+	KUNIT_CASE(damon_test_apply_three_regions3),
+	KUNIT_CASE(damon_test_apply_three_regions4),
+	KUNIT_CASE(damon_test_split_evenly),
+	KUNIT_CASE(damon_test_split_at),
+	KUNIT_CASE(damon_test_merge_two),
+	KUNIT_CASE(damon_test_merge_regions_of),
+	KUNIT_CASE(damon_test_split_regions_of),
+	{},
+};
+
+static struct kunit_suite damon_test_suite = {
+	.name = "damon",
+	.test_cases = damon_test_cases,
+};
+kunit_test_suite(damon_test_suite);
+
+#endif /* _DAMON_TEST_H */
+
+#endif	/* CONFIG_DAMON_KUNIT_TEST */
diff --git a/mm/damon.c b/mm/damon.c
index e99500c9f7c3..e7301c90d690 100644
--- a/mm/damon.c
+++ b/mm/damon.c
@@ -36,7 +36,11 @@
 #include <trace/events/damon.h>
 
 /* Minimal region size.  Every damon_region is aligned by this. */
+#ifndef CONFIG_DAMON_KUNIT_TEST
 #define MIN_REGION PAGE_SIZE
+#else
+#define MIN_REGION 1
+#endif
 
 /*
  * Functions and macros for DAMON data structures
@@ -1624,3 +1628,5 @@ module_exit(damon_exit);
 MODULE_LICENSE("GPL");
 MODULE_AUTHOR("SeongJae Park <sjpark@amazon.de>");
 MODULE_DESCRIPTION("DAMON: Data Access MONitor");
+
+#include "damon-test.h"
-- 
2.17.1

[PATCH v17 14/15] mm/damon: Add user space selftests

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds a simple user space tests for DAMON.  The tests are
using kselftest framework.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/testing/selftests/damon/Makefile        |   7 +
 .../selftests/damon/_chk_dependency.sh        |  28 ++++
 tools/testing/selftests/damon/_chk_record.py  | 108 ++++++++++++++
 .../testing/selftests/damon/debugfs_attrs.sh  | 139 ++++++++++++++++++
 .../testing/selftests/damon/debugfs_record.sh |  50 +++++++
 5 files changed, 332 insertions(+)
 create mode 100644 tools/testing/selftests/damon/Makefile
 create mode 100644 tools/testing/selftests/damon/_chk_dependency.sh
 create mode 100644 tools/testing/selftests/damon/_chk_record.py
 create mode 100755 tools/testing/selftests/damon/debugfs_attrs.sh
 create mode 100755 tools/testing/selftests/damon/debugfs_record.sh

diff --git a/tools/testing/selftests/damon/Makefile b/tools/testing/selftests/damon/Makefile
new file mode 100644
index 000000000000..cfd5393a4639
--- /dev/null
+++ b/tools/testing/selftests/damon/Makefile
@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+# Makefile for damon selftests
+
+TEST_FILES = _chk_dependency.sh _chk_record_file.py
+TEST_PROGS = debugfs_attrs.sh debugfs_record.sh
+
+include ../lib.mk
diff --git a/tools/testing/selftests/damon/_chk_dependency.sh b/tools/testing/selftests/damon/_chk_dependency.sh
new file mode 100644
index 000000000000..814dcadd5e96
--- /dev/null
+++ b/tools/testing/selftests/damon/_chk_dependency.sh
@@ -0,0 +1,28 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+DBGFS=/sys/kernel/debug/damon
+
+if [ $EUID -ne 0 ];
+then
+	echo "Run as root"
+	exit $ksft_skip
+fi
+
+if [ ! -d $DBGFS ]
+then
+	echo "$DBGFS not found"
+	exit $ksft_skip
+fi
+
+for f in attrs record pids monitor_on
+do
+	if [ ! -f "$DBGFS/$f" ]
+	then
+		echo "$f not found"
+		exit 1
+	fi
+done
diff --git a/tools/testing/selftests/damon/_chk_record.py b/tools/testing/selftests/damon/_chk_record.py
new file mode 100644
index 000000000000..5cfcf4161404
--- /dev/null
+++ b/tools/testing/selftests/damon/_chk_record.py
@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"Check whether the DAMON record file is valid"
+
+import argparse
+import struct
+import sys
+
+fmt_version = 0
+
+def set_fmt_version(f):
+    global fmt_version
+
+    mark = f.read(16)
+    if mark == b'damon_recfmt_ver':
+        fmt_version = struct.unpack('i', f.read(4))[0]
+    else:
+        fmt_version = 0
+        f.seek(0)
+    return fmt_version
+
+def read_pid(f):
+    if fmt_version == 0:
+        pid = struct.unpack('L', f.read(8))[0]
+    else:
+        pid = struct.unpack('i', f.read(4))[0]
+def err_percent(val, expected):
+    return abs(val - expected) / expected * 100
+
+def chk_task_info(f):
+    pid = read_pid(f)
+    nr_regions = struct.unpack('I', f.read(4))[0]
+
+    if nr_regions > max_nr_regions:
+        print('too many regions: %d > %d' % (nr_regions, max_nr_regions))
+        exit(1)
+
+    nr_gaps = 0
+    eaddr = 0
+    for r in range(nr_regions):
+        saddr = struct.unpack('L', f.read(8))[0]
+        if eaddr and saddr != eaddr:
+            nr_gaps += 1
+        eaddr = struct.unpack('L', f.read(8))[0]
+        nr_accesses = struct.unpack('I', f.read(4))[0]
+
+        if saddr >= eaddr:
+            print('wrong region [%d,%d)' % (saddr, eaddr))
+            exit(1)
+
+        max_nr_accesses = aint / sint
+        if nr_accesses > max_nr_accesses:
+            if err_percent(nr_accesses, max_nr_accesses) > 15:
+                print('too high nr_access: expected %d but %d' %
+                        (max_nr_accesses, nr_accesses))
+                exit(1)
+    if nr_gaps != 2:
+        print('number of gaps are not two but %d' % nr_gaps)
+        exit(1)
+
+def parse_time_us(bindat):
+    sec = struct.unpack('l', bindat[0:8])[0]
+    nsec = struct.unpack('l', bindat[8:16])[0]
+    return (sec * 1000000000 + nsec) / 1000
+
+def main():
+    global sint
+    global aint
+    global min_nr
+    global max_nr_regions
+
+    parser = argparse.ArgumentParser()
+    parser.add_argument('file', metavar='<file>',
+            help='path to the record file')
+    parser.add_argument('--attrs', metavar='<attrs>',
+            default='5000 100000 1000000 10 1000',
+            help='content of debugfs attrs file')
+    args = parser.parse_args()
+    file_path = args.file
+    attrs = [int(x) for x in args.attrs.split()]
+    sint, aint, rint, min_nr, max_nr_regions = attrs
+
+    with open(file_path, 'rb') as f:
+        set_fmt_version(f)
+        last_aggr_time = None
+        while True:
+            timebin = f.read(16)
+            if len(timebin) != 16:
+                break
+
+            now = parse_time_us(timebin)
+            if not last_aggr_time:
+                last_aggr_time = now
+            else:
+                error = err_percent(now - last_aggr_time, aint)
+                if error > 15:
+                    print('wrong aggr interval: expected %d, but %d' %
+                            (aint, now - last_aggr_time))
+                    exit(1)
+                last_aggr_time = now
+
+            nr_tasks = struct.unpack('I', f.read(4))[0]
+            for t in range(nr_tasks):
+                chk_task_info(f)
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/testing/selftests/damon/debugfs_attrs.sh b/tools/testing/selftests/damon/debugfs_attrs.sh
new file mode 100755
index 000000000000..d5188b0f71b1
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_attrs.sh
@@ -0,0 +1,139 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./_chk_dependency.sh
+
+# Test attrs file
+file="$DBGFS/attrs"
+
+ORIG_CONTENT=$(cat $file)
+
+echo 1 2 3 4 5 > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write failed"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo 1 2 3 4 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file write success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2 3 4 5" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+# Test record file
+file="$DBGFS/record"
+
+ORIG_CONTENT=$(cat $file)
+
+echo "4242 foo.bar" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file writing sane input failed"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo abc 2 3 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file writing insane input 1 success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo 123 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file writing insane input 2 success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "4242 foo.bar" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "0 null" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file disabling write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "0 null" ]
+then
+	echo "$file not disabled"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "4242 foo.bar" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file writing sane data again fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+# Test pids file
+file="$DBGFS/pids"
+
+ORIG_CONTENT=$(cat $file)
+
+echo "1 2 3 4" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "1 2 abc 4" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo abc 2 3 > $file
+if [ $? -eq 0 ]
+then
+	echo "$file write success (should failed)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+CONTENT=$(cat $file)
+if [ "$CONTENT" != "1 2" ]
+then
+	echo "$file not written"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo $ORIG_CONTENT > $file
+
+echo "PASS"
diff --git a/tools/testing/selftests/damon/debugfs_record.sh b/tools/testing/selftests/damon/debugfs_record.sh
new file mode 100755
index 000000000000..fa9e07eea258
--- /dev/null
+++ b/tools/testing/selftests/damon/debugfs_record.sh
@@ -0,0 +1,50 @@
+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+
+source ./_chk_dependency.sh
+
+restore_attrs()
+{
+	echo $ORIG_ATTRS > $DBGFS/attrs
+	echo $ORIG_PIDS > $DBGFS/pids
+	echo $ORIG_RECORD > $DBGFS/record
+}
+
+ORIG_ATTRS=$(cat $DBGFS/attrs)
+ORIG_PIDS=$(cat $DBGFS/pids)
+ORIG_RECORD=$(cat $DBGFS/record)
+
+rfile=$pwd/damon.data
+
+rm -f $rfile
+ATTRS="5000 100000 1000000 10 1000"
+echo $ATTRS > $DBGFS/attrs
+echo 4096 $rfile > $DBGFS/record
+sleep 5 &
+echo $(pidof sleep) > $DBGFS/pids
+echo on > $DBGFS/monitor_on
+sleep 0.5
+killall sleep
+echo off > $DBGFS/monitor_on
+
+sync
+
+if [ ! -f $rfile ]
+then
+	echo "record file not made"
+	restore_attrs
+
+	exit 1
+fi
+
+python3 ./_chk_record.py $rfile --attrs "$ATTRS"
+if [ $? -ne 0 ]
+then
+	echo "record file is wrong"
+	restore_attrs
+	exit 1
+fi
+
+rm -f $rfile
+restore_attrs
+echo "PASS"
-- 
2.17.1

[PATCH v17 15/15] MAINTAINERS: Update for DAMON

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit updates MAINTAINERS file for DAMON related files.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 MAINTAINERS | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/MAINTAINERS b/MAINTAINERS
index 50659d76976b..2396a9098715 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -4686,6 +4686,18 @@ F:	net/ax25/ax25_out.c
 F:	net/ax25/ax25_timer.c
 F:	net/ax25/sysctl_net_ax25.c
 
+DATA ACCESS MONITOR
+M:	SeongJae Park <sjpark@amazon.de>
+L:	linux-mm@kvack.org
+S:	Maintained
+F:	Documentation/admin-guide/mm/damon/*
+F:	include/linux/damon.h
+F:	include/trace/events/damon.h
+F:	mm/damon-test.h
+F:	mm/damon.c
+F:	tools/damon/*
+F:	tools/testing/selftests/damon/*
+
 DAVICOM FAST ETHERNET (DMFE) NETWORK DRIVER
 L:	netdev@vger.kernel.org
 S:	Orphan
-- 
2.17.1

Re: [PATCH v17 11/15] tools/damon/wss: Implement '--thres' option

[SeongJae Park]

On Mon, 6 Jul 2020 13:53:18 +0200 SeongJae Park <sjpark@amazon.com> wrote:

> From: SeongJae Park <sjpark@amazon.de>
> 
> Currently, 'wss' treats every region as working set if accessed at least
> once.  Someone who want to know performance important working set only
> would want to ignore regions having low access frequency.  '--thres'
> option can be used to set the minimal access frequency of the regions to
> be classified as the workingset.
> 
> Using this, users can plot the reuse histogram.  For example:
> 
>     $ damo record $(pidof raytrace)
>     $ for t in {1..20}; do ./tools/damon/damo report wss --thres $t | \
>     		grep avr | awk -v reuse_time=$(( (21 - t) * 5 )) \
>     		'{print reuse_time " " $3}'; done
>     100 12838416
>     95 2222623
>     90 1585480
>     85 422890
>     80 67040
>     75 45218
>     70 13242
>     65 12896
>     60 12136
>     55 10872
>     50 9648
>     45 8136
>     40 7052
>     35 6304
>     30 5736
>     25 5404
>     20 5305
>     15 5187
>     10 5069
>     5 4873
> 
> Above command shows the reuse histogram of parsec3.raytrace.  Remind
> that the sampling interval and aggregation interval are 5ms and 100ms
> by default and this command used the default values.  So, the above
> output means that about 12MB of memory region was reused within 100 ms
> while only about 2MB of memory region was reused within 95 ms, then
> about 1.5MB within 90ms, and so on, in average.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> ---
>  tools/damon/wss.py | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/damon/wss.py b/tools/damon/wss.py
> index b43065176cfd..d2a1b149e3ea 100644
> --- a/tools/damon/wss.py
> +++ b/tools/damon/wss.py
> @@ -17,6 +17,8 @@ def set_argparser(parser):
>      parser.add_argument('--range', '-r', type=int, nargs=3,
>              metavar=('<start>', '<stop>', '<step>'),
>              help='range of wss percentiles to print')
> +    parser.add_argument('--thres', '-t', type=int, metavar='<# accesses>',
> +            help='minimal number of accesses for treated as working set')
>      parser.add_argument('--sortby', '-s', choices=['time', 'size'],
>              help='the metric to be used for the sort of the working set sizes')
>      parser.add_argument('--plot', '-p', type=str, metavar='<file>',
> @@ -67,7 +69,7 @@ def main(args=None):
>              wss = 0
>              for p in snapshot:
>                  # Ignore regions not accessed
> -                if p[1] <= 0:
> +                if p[1] < args.thres:

Oops, I forgot giving default value for the option.  I will set it as 1 in the
next spin.


Thanks,
SeongJae Park

>                      continue
>                  wss += p[0]
>              wss_dist.append(wss)
> -- 
> 2.17.1
> 
> 
> 

Re: [PATCH v17 12/15] Documentation/admin-guide/mm: Add a document for DAMON

[Mike Rapoport]

Hello SeongJae,

On Mon, Jul 06, 2020 at 01:53:19PM +0200, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit adds a document for DAMON under
> `Documentation/admin-guide/mm/damon/`.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> ---
>  Documentation/admin-guide/mm/damon/api.rst    |  20 ++
>  .../admin-guide/mm/damon/damon_heatmap.png    | Bin 0 -> 8366 bytes
>  .../admin-guide/mm/damon/damon_wss_change.png | Bin 0 -> 7211 bytes
>  .../admin-guide/mm/damon/damon_wss_dist.png   | Bin 0 -> 6173 bytes
>  Documentation/admin-guide/mm/damon/eval.rst   | 222 +++++++++++++
>  Documentation/admin-guide/mm/damon/faq.rst    |  59 ++++
>  .../admin-guide/mm/damon/freqmine_heatmap.png | Bin 0 -> 9999 bytes
>  .../admin-guide/mm/damon/freqmine_wss_sz.png  | Bin 0 -> 5589 bytes
>  .../mm/damon/freqmine_wss_time.png            | Bin 0 -> 6550 bytes
>  Documentation/admin-guide/mm/damon/guide.rst  | 194 ++++++++++++
>  Documentation/admin-guide/mm/damon/index.rst  |  35 +++
>  .../admin-guide/mm/damon/mechanisms.rst       | 159 ++++++++++
>  Documentation/admin-guide/mm/damon/plans.rst  |  29 ++
>  Documentation/admin-guide/mm/damon/start.rst  | 117 +++++++
>  .../mm/damon/streamcluster_heatmap.png        | Bin 0 -> 42210 bytes
>  .../mm/damon/streamcluster_wss_sz.png         | Bin 0 -> 6327 bytes
>  .../mm/damon/streamcluster_wss_time.png       | Bin 0 -> 8830 bytes
>  Documentation/admin-guide/mm/damon/usage.rst  | 296 ++++++++++++++++++
>  Documentation/admin-guide/mm/index.rst        |   1 +

It's really cool to see documentation along with the code!

I'd suggest to reorganize the DAMON docs to better match the current
structure of Documentation/ directory.

The description of DAMON usage from the userspace and reference for the
userland tools does belong to Documentation/admin-guide/mm. However, the
kernel APIs are better to be placed in Documentation/core-api or even
Documentation/dev-tools. As for the detailed description of the internal
DAMON operation, this would naturally belong to Documentation/vm.

Another thing is that this patch is really hard to review because of the
encoded png blobs. In general, we try to keep Documentation/ readable in
plain text, but if you think that the images are essential and must be a
part of DAMON in-tree docs rather than links to an external resource,
please split them to a separate patch.

-- 
Sincerely yours,
Mike.

Re: [PATCH v17 03/15] mm/damon: Implement region based sampling

[SeongJae Park]

On Mon, 6 Jul 2020 13:53:10 +0200 SeongJae Park <sjpark@amazon.com> wrote:

> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit implements DAMON's target address space independent high
> level logics for basic access check and region based sampling.  This
> doesn't work alone, but needs the target address space specific low
> level pritimives implementation for the monitoring target address ranges
> construction and the access check, though.  A reference implementation
> of those will be provided by a later commit.  Nevertheless, users can
> implement and use their own versions for their specific use cases.
>
[...]
> +/**
> + * damon_start() - Starts monitoring with given context.
> + * @ctx:	monitoring context
> + *
> + * Return: 0 on success, negative error code otherwise.
> + */
> +int damon_start(struct damon_ctx *ctx)
> +{
> +	int err = -EBUSY;
> +
> +	mutex_lock(&ctx->kdamond_lock);
> +	if (!ctx->kdamond) {
> +		err = 0;
> +		ctx->kdamond_stop = false;
> +		ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond");

Oops, this means 'kdamond_fn' could see the unset '->kdamond'.  I will use
'kthread_create()' and 'wake_up_process()' in the next spin.

> +		if (IS_ERR(ctx->kdamond))
> +			err = PTR_ERR(ctx->kdamond);
> +	}
> +	mutex_unlock(&ctx->kdamond_lock);
> +
> +	return err;
> +}

So, the change would be something like below:

--- a/mm/damon.c
+++ b/mm/damon.c
@@ -1464,9 +1464,11 @@ int damon_start(struct damon_ctx *ctx)
        if (!ctx->kdamond) {
                err = 0;
                ctx->kdamond_stop = false;
-               ctx->kdamond = kthread_run(kdamond_fn, ctx, "kdamond");
+               ctx->kdamond = kthread_create(kdamond_fn, ctx, "kdamond");
                if (IS_ERR(ctx->kdamond))
                        err = PTR_ERR(ctx->kdamond);
+               else
+                       wake_up_process(ctx->kdamond);
        }
        mutex_unlock(&ctx->kdamond_lock);


Thanks,
SeongJae Park

Re: Re: [PATCH v17 12/15] Documentation/admin-guide/mm: Add a document for DAMON

[SeongJae Park]

On Tue, 7 Jul 2020 10:49:06 +0300 Mike Rapoport <rppt@kernel.org> wrote:

> Hello SeongJae,
> 
> On Mon, Jul 06, 2020 at 01:53:19PM +0200, SeongJae Park wrote:
> > From: SeongJae Park <sjpark@amazon.de>
> > 
> > This commit adds a document for DAMON under
> > `Documentation/admin-guide/mm/damon/`.
> > 
> > Signed-off-by: SeongJae Park <sjpark@amazon.de>
> > ---
> >  Documentation/admin-guide/mm/damon/api.rst    |  20 ++
> >  .../admin-guide/mm/damon/damon_heatmap.png    | Bin 0 -> 8366 bytes
> >  .../admin-guide/mm/damon/damon_wss_change.png | Bin 0 -> 7211 bytes
> >  .../admin-guide/mm/damon/damon_wss_dist.png   | Bin 0 -> 6173 bytes
> >  Documentation/admin-guide/mm/damon/eval.rst   | 222 +++++++++++++
> >  Documentation/admin-guide/mm/damon/faq.rst    |  59 ++++
> >  .../admin-guide/mm/damon/freqmine_heatmap.png | Bin 0 -> 9999 bytes
> >  .../admin-guide/mm/damon/freqmine_wss_sz.png  | Bin 0 -> 5589 bytes
> >  .../mm/damon/freqmine_wss_time.png            | Bin 0 -> 6550 bytes
> >  Documentation/admin-guide/mm/damon/guide.rst  | 194 ++++++++++++
> >  Documentation/admin-guide/mm/damon/index.rst  |  35 +++
> >  .../admin-guide/mm/damon/mechanisms.rst       | 159 ++++++++++
> >  Documentation/admin-guide/mm/damon/plans.rst  |  29 ++
> >  Documentation/admin-guide/mm/damon/start.rst  | 117 +++++++
> >  .../mm/damon/streamcluster_heatmap.png        | Bin 0 -> 42210 bytes
> >  .../mm/damon/streamcluster_wss_sz.png         | Bin 0 -> 6327 bytes
> >  .../mm/damon/streamcluster_wss_time.png       | Bin 0 -> 8830 bytes
> >  Documentation/admin-guide/mm/damon/usage.rst  | 296 ++++++++++++++++++
> >  Documentation/admin-guide/mm/index.rst        |   1 +
> 
> It's really cool to see documentation along with the code!
> 
> I'd suggest to reorganize the DAMON docs to better match the current
> structure of Documentation/ directory.
> 
> The description of DAMON usage from the userspace and reference for the
> userland tools does belong to Documentation/admin-guide/mm. However, the
> kernel APIs are better to be placed in Documentation/core-api or even
> Documentation/dev-tools. As for the detailed description of the internal
> DAMON operation, this would naturally belong to Documentation/vm.
> 
> Another thing is that this patch is really hard to review because of the
> encoded png blobs. In general, we try to keep Documentation/ readable in
> plain text, but if you think that the images are essential and must be a
> part of DAMON in-tree docs rather than links to an external resource,
> please split them to a separate patch.

Totally agreed!  Thanks for the kind and wise comments.  I will try to remove
the blobs or at least separate those in the next spin.


Thanks,
SeongJae Park

> 
> -- 
> Sincerely yours,
> Mike.
>