[RFC v15.1 0/8] Implement Data Access Monitoring-based Memory Operation Schemes

[RFC v15.1 0/8] Implement Data Access Monitoring-based Memory Operation Schemes

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

NOTE: This is only an RFC for future features of DAMON patchset[1], which is
not merged in the mainline yet.  The aim of this RFC is to show how DAMON would
be evolved once it is merged in.  So, if you have some interest in this RFC,
please consider reviewing the DAMON patchset, either.

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

Only below minor changes made on v15 of this patchset.  Therefore I'm setting
the version number to v15.1 rather than v16.

- Rebase on v5.10 + DAMON v23[1]
- Drop the dependency on Minchan's out-of-tree patch (It's merged in v5.10)

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

DAMON[1] can be used as a primitive for data access aware memory management
optimizations.  For that, users who want such optimizations should run DAMON,
read the monitoring results, analyze it, plan a new memory management scheme,
and apply the new scheme by themselves.  Such efforts will be inevitable for
some complicated optimizations.

However, in many other cases, the users would simply want the system to apply a
memory management action to a memory region of a specific size having a
specific access frequency for a specific time.  For example, "page out a memory
region larger than 100 MiB keeping only rare accesses more than 2 minutes", or
"Do not use THP for a memory region larger than 2 MiB rarely accessed for more
than 1 seconds".

This RFC patchset makes DAMON to handle such data access monitoring-based
Operation Schemes (DAMOS).  With this change, users can do the data access
aware optimizations by simply specifying their schemes.

[1] https://lore.kernel.org/linux-mm/20201215115448.25633-1-sjpark@amazon.com

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

We evaluated DAMON's overhead, monitoring quality and usefulness using 24
realistic workloads on my QEMU/KVM based virtual machine running a kernel that
v23 DAMON patchset is applied.

DAMON is lightweight.  It increases system memory usage by 0.42% and slows
target workloads down by 0.39%.

DAMON is accurate and useful for memory management optimizations.  An
experimental DAMON-based operation scheme for THP, 'ethp', removes 81.45% of
THP memory overheads while preserving 50.09% of THP speedup.  Another
experimental DAMON-based 'proactive reclamation' implementation, 'prcl',
reduces 91.45% of residential sets and 22.91% of system memory footprint while
incurring only 2.43% runtime overhead in the best case (parsec3/freqmine).

NOTE that the experimental THP optimization and proactive reclamation are not
for production but 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-damos
[3] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.0.html
[4] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.html
[5] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.2.html
[6] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.html
[7] https://damonitor.github.io/test/result/visual/latest/rec.wss_time.html
[8] https://damonitor.github.io/test/result/perf/latest/html/index.html

Baseline and Complete Git Tree
==============================

The patches are based on the v5.10 plus v23 DAMON patchset[1].  You can also
clone the complete git tree:

    $ git clone git://github.com/sjp38/linux -b damos/rfc/v15.1

The web is also available:
https://github.com/sjp38/linux/releases/tag/damos/rfc/v15.1

There are a couple of trees for entire DAMON patchset series that future
features are included.  The first one[3] contains the changes for latest
release, while the other one[4] contains the changes for next release.

[1] https://lore.kernel.org/linux-doc/20201005105522.23841-1-sjpark@amazon.com/
[2] https://lore.kernel.org/linux-mm/20200302193630.68771-2-minchan@kernel.org/
[3] https://github.com/sjp38/linux/tree/damon/master
[4] https://github.com/sjp38/linux/tree/damon/next

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

The 1st patch accounts age of each region.  The 2nd patch implements the
core of the DAMON-based operation schemes feature.  The 3rd patch makes
the default monitoring primitives for virtual address spaces to support the
schemes.  From this point, the kernel space users can use DAMOS.  The 4th patch
exports the feature to the user space via the debugfs interface.  The 5th patch
implements schemes statistics feature for easier tuning of the schemes and
runtime access pattern analysis.  The 6th patch adds selftests for these
changes, and the 7th patch adds human friendly schemes support to the user
space tool for DAMON.  Finally, the 8th patch documents this new feature.

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

Changes from RFC v15
(https://lore.kernel.org/linux-mm/20201006123931.5847-1-sjpark@amazon.com/)
- Rebase on v5.10 + DAMON v23[1]
- Drop the dependency on Minchan's out-of-tree patch (It's merged in v5.10)

Changes from RFC v14
(https://lore.kernel.org/linux-mm/20200804142430.15384-1-sjpark@amazon.com/)
- s/snprintf()/scnprintf() (Marco Elver)
- Place three parts of DAMON (core, primitives, and dbgfs) in different files

Changes from RFC v13
(https://lore.kernel.org/linux-mm/20200707093805.4775-1-sjpark@amazon.com/)
- Drop loadable module support
- Use dedicated valid action checker function
- Rebase on v5.8 plus v19 DAMON

Changes from RFC v12
(https://lore.kernel.org/linux-mm/20200616073828.16509-1-sjpark@amazon.com/)
 - Wordsmith the document, comment, commit messages
 - Support a scheme of max access count 0
 - Use 'unsigned long' for (min|max)_sz_region

Changes from RFC v11
(https://lore.kernel.org/linux-mm/20200609065320.12941-1-sjpark@amazon.com/)
 - Refine the commit messages (David Hildenbrand)
 - Clean up debugfs code

Changes from RFC v10
(https://lore.kernel.org/linux-mm/20200603071138.8152-1-sjpark@amazon.com/)
 - Fix the wrong error handling for schemes debugfs file
 - Handle the schemes stats from the user space tool
 - Remove the schemes implementation plan from the document

Changes from RFC v9
(https://lore.kernel.org/linux-mm/20200526075702.27339-1-sjpark@amazon.com/)
 - Rebase on v5.7
 - Fix wrong comments and documents for schemes apply conditions

Changes from RFC v8
(https://lore.kernel.org/linux-mm/20200512115343.27699-1-sjpark@amazon.com/)
 - Rewrite the document (Stefan Nuernberger)
 - Make 'damon_for_each_*' argument order consistent (Leonard Foerster)
 - Implement statistics for schemes
 - Avoid races between debugfs readers and writers
 - Reset age for only significant access frequency changes
 - Add kernel-doc comments in damon.h

Please refer to RFC v8 for previous history

SeongJae Park (8):
  mm/damon/core: Account age of target regions
  mm/damon/core: Implement DAMON-based Operation Schemes (DAMOS)
  mm/damon/vaddr: Support DAMON-based Operation Schemes
  mm/damon/dbgfs: Support DAMON-based Operation Schemes
  mm/damon/schemes: Implement statistics feature
  selftests/damon: Add 'schemes' debugfs tests
  tools/damon: Support more human friendly 'schemes' control
  Docs/admin-guide/mm/damon: Document DAMON-based Operation Schemes

 Documentation/admin-guide/mm/damon/guide.rst  |  41 ++++-
 Documentation/admin-guide/mm/damon/start.rst  |  11 ++
 Documentation/admin-guide/mm/damon/usage.rst  | 109 ++++++++++-
 Documentation/vm/damon/index.rst              |   1 -
 include/linux/damon.h                         |  92 +++++++++-
 mm/damon/core.c                               | 125 +++++++++++++
 mm/damon/dbgfs.c                              | 170 +++++++++++++++++-
 mm/damon/vaddr.c                              |  58 ++++++
 tools/damon/_convert_damos.py                 | 141 +++++++++++++++
 tools/damon/_damon.py                         |  28 ++-
 tools/damon/damo                              |   7 +
 tools/damon/schemes.py                        | 110 ++++++++++++
 .../testing/selftests/damon/debugfs_attrs.sh  |  29 +++
 13 files changed, 903 insertions(+), 19 deletions(-)
 create mode 100755 tools/damon/_convert_damos.py
 create mode 100644 tools/damon/schemes.py

-- 
2.17.1

[RFC v15.1 1/8] mm/damon/core: Account age of target regions

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

DAMON can be used for data access pattern aware memory management
optimizations.  For that, users should run DAMON, read the monitoring
results, analyze it, plan a new memory management scheme, and apply the
new scheme by themselves.  It would not be too hard, but still require
some level of effort.  For complicated cases, this effort is inevitable.

That said, in many cases, users would simply want to apply an actions to
a memory region of a specific size having a specific access frequency
for a specific time.  For example, "page out a memory region larger than
100 MiB but having a low access frequency more than 10 minutes", or "Use
THP for a memory region larger than 2 MiB having a high access frequency
for more than 2 seconds".

For such optimizations, users will need to first account the age of each
region themselves.  To reduce such efforts, this commit implements a
simple age account of each region in DAMON.  For each aggregation step,
DAMON compares the access frequency with that from last aggregation and
reset the age of the region if the change is significant.  Else, the age
is incremented.  Also, in case of the merge of regions, the region
size-weighted average of the ages is set as the age of merged new
region.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h | 10 ++++++++++
 mm/damon/core.c       | 13 +++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index f9e0d4349352..ca7b7e8a0025 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -31,12 +31,22 @@ struct damon_addr_range {
  * @sampling_addr:	Address of the sample for the next access check.
  * @nr_accesses:	Access frequency of this region.
  * @list:		List head for siblings.
+ * @age:		Age of this region.
+ * @last_nr_accesses:	Internal value for age calculation.
+ *
+ * @age is initially zero, increased for each aggregation interval, and reset
+ * to zero again if the access frequency is significantly changed.  If two
+ * regions are merged into a new region, both @nr_accesses and @age of the new
+ * region are set as region size-weighted average of those of the two regions.
  */
 struct damon_region {
 	struct damon_addr_range ar;
 	unsigned long sampling_addr;
 	unsigned int nr_accesses;
 	struct list_head list;
+
+	unsigned int age;
+	unsigned int last_nr_accesses;
 };
 
 /**
diff --git a/mm/damon/core.c b/mm/damon/core.c
index 214ff404a423..c4d4114a7545 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -45,6 +45,9 @@ struct damon_region *damon_new_region(unsigned long start, unsigned long end)
 	region->nr_accesses = 0;
 	INIT_LIST_HEAD(&region->list);
 
+	region->age = 0;
+	region->last_nr_accesses = 0;
+
 	return region;
 }
 
@@ -439,6 +442,7 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 
 		damon_for_each_region(r, t) {
 			trace_damon_aggregated(t, r, damon_nr_regions(t));
+			r->last_nr_accesses = r->nr_accesses;
 			r->nr_accesses = 0;
 		}
 	}
@@ -456,6 +460,7 @@ static void damon_merge_two_regions(struct damon_region *l,
 
 	l->nr_accesses = (l->nr_accesses * sz_l + r->nr_accesses * sz_r) /
 			(sz_l + sz_r);
+	l->age = (l->age * sz_l + r->age * sz_r) / (sz_l + sz_r);
 	l->ar.end = r->ar.end;
 	damon_destroy_region(r);
 }
@@ -475,6 +480,11 @@ static void damon_merge_regions_of(struct damon_target *t, unsigned int thres,
 	struct damon_region *r, *prev = NULL, *next;
 
 	damon_for_each_region_safe(r, next, t) {
+		if (diff_of(r->nr_accesses, r->last_nr_accesses) > thres)
+			r->age = 0;
+		else
+			r->age++;
+
 		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)
@@ -518,6 +528,9 @@ static void damon_split_region_at(struct damon_ctx *ctx,
 	new = damon_new_region(r->ar.start + sz_r, r->ar.end);
 	r->ar.end = new->ar.start;
 
+	new->age = r->age;
+	new->last_nr_accesses = r->last_nr_accesses;
+
 	damon_insert_region(new, r, damon_next_region(r));
 }
 
-- 
2.17.1

[RFC v15.1 2/8] mm/damon/core: Implement DAMON-based Operation Schemes (DAMOS)

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

In many cases, users might use DAMON for simple data access aware
memory management optimizations such as applying an operation scheme to
a memory region of a specific size having a specific access frequency
for a specific time.  For example, "page out a memory region larger than
100 MiB but having a low access frequency more than 10 minutes", or "Use
THP for a memory region larger than 2 MiB having a high access frequency
for more than 2 seconds".

Most simple form of the solution would be doing offline data access
pattern profiling using DAMON and modifying the application source code
or system configuration based on the profiling results.  Or, developing
a daemon constructed with two modules (one for access monitoring and the
other for applying memory management actions via mlock(), madvise(),
sysctl, etc) is imaginable.

To avoid users spending their time for implementation of such simple
data access monitoring-based operation schemes, this commit makes DAMON
to handle such schemes directly.  With this commit, users can simply
specify their desired schemes to DAMON.  Then, DAMON will automatically
apply the schemes to the user-specified target processes.

Each of the schemes is composed with conditions for filtering of the
target memory regions and desired memory management action for the
target.  Specifically, the format is::

    <min/max size> <min/max access frequency> <min/max age> <action>

The filtering conditions are size of memory region, number of accesses
to the region monitored by DAMON, and the age of the region.  The age of
region is incremented periodically but reset when its addresses or
access frequency has significantly changed or the action of a scheme was
applied.  For the action, current implementation supports a few of
madvise()-like hints, ``WILLNEED``, ``COLD``, ``PAGEOUT``, ``HUGEPAGE``,
and ``NOHUGEPAGE``.

Because DAMON supports various address spaces and application of the
actions to a monitoring target region is dependent to the type of the
target address space, the application code should be implemented by each
primitives and registered to the framework.  Note that this commit only
implements the framework part.  Following commit will implement the
action applications for virtual address spaces primitives.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h |  72 ++++++++++++++++++++++++++--
 mm/damon/core.c       | 107 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 176 insertions(+), 3 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index ca7b7e8a0025..cfcd399da134 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -67,6 +67,48 @@ struct damon_target {
 	struct list_head list;
 };
 
+/**
+ * enum damos_action - Represents an action of a Data Access Monitoring-based
+ * Operation Scheme.
+ *
+ * @DAMOS_WILLNEED:	Call ``madvise()`` for the region with MADV_WILLNEED.
+ * @DAMOS_COLD:		Call ``madvise()`` for the region with MADV_COLD.
+ * @DAMOS_PAGEOUT:	Call ``madvise()`` for the region with MADV_PAGEOUT.
+ * @DAMOS_HUGEPAGE:	Call ``madvise()`` for the region with MADV_HUGEPAGE.
+ * @DAMOS_NOHUGEPAGE:	Call ``madvise()`` for the region with MADV_NOHUGEPAGE.
+ */
+enum damos_action {
+	DAMOS_WILLNEED,
+	DAMOS_COLD,
+	DAMOS_PAGEOUT,
+	DAMOS_HUGEPAGE,
+	DAMOS_NOHUGEPAGE,
+};
+
+/**
+ * struct damos - Represents a Data Access Monitoring-based Operation Scheme.
+ * @min_sz_region:	Minimum size of target regions.
+ * @max_sz_region:	Maximum size of target regions.
+ * @min_nr_accesses:	Minimum ``->nr_accesses`` of target regions.
+ * @max_nr_accesses:	Maximum ``->nr_accesses`` of target regions.
+ * @min_age_region:	Minimum age of target regions.
+ * @max_age_region:	Maximum age of target regions.
+ * @action:		&damo_action to be applied to the target regions.
+ * @list:		List head for siblings.
+ *
+ * Note that both the minimums and the maximums are inclusive.
+ */
+struct damos {
+	unsigned long min_sz_region;
+	unsigned long max_sz_region;
+	unsigned int min_nr_accesses;
+	unsigned int max_nr_accesses;
+	unsigned int min_age_region;
+	unsigned int max_age_region;
+	enum damos_action action;
+	struct list_head list;
+};
+
 struct damon_ctx;
 
 /**
@@ -77,6 +119,7 @@ struct damon_ctx;
  * @prepare_access_checks:	Prepares next access check of target regions.
  * @check_accesses:		Checks the access of target regions.
  * @reset_aggregated:		Resets aggregated accesses monitoring results.
+ * @apply_scheme:		Apply a DAMON-based operation scheme.
  * @target_valid:		Determine if the target is valid.
  * @cleanup:			Cleans up the context.
  *
@@ -103,6 +146,9 @@ struct damon_ctx;
  * of its update.
  * @reset_aggregated should reset the access monitoring results that aggregated
  * by @check_accesses.
+ * @apply_scheme is called from @kdamond when a region for user provided
+ * DAMON-based operation scheme is found.  It should apply the scheme's action
+ * to the region.  This is not used for &DAMON_ARBITRARY_TARGET case.
  * @target_valid should check whether the target is still valid for the
  * monitoring.  It receives &damon_ctx.arbitrary_target or &struct damon_target
  * pointer depends on &damon_ctx.target_type.
@@ -115,6 +161,8 @@ struct damon_primitive {
 	void (*prepare_access_checks)(struct damon_ctx *context);
 	unsigned int (*check_accesses)(struct damon_ctx *context);
 	void (*reset_aggregated)(struct damon_ctx *context);
+	int (*apply_scheme)(struct damon_ctx *context, struct damon_target *t,
+			struct damon_region *r, struct damos *scheme);
 	bool (*target_valid)(void *target);
 	void (*cleanup)(struct damon_ctx *context);
 };
@@ -205,12 +253,13 @@ enum damon_target_type {
  * @min_nr_regions:	The minimum number of adaptive monitoring regions.
  * @max_nr_regions:	The maximum number of adaptive monitoring regions.
  * @adaptive_targets:	Head of monitoring targets (&damon_target) list.
+ * @schemes:		Head of schemes (&damos) list.
  *
  * @arbitrary_target:	Pointer to arbitrary type target.
  *
- * @min_nr_regions, @max_nr_regions and @adaptive_targets are valid only if
- * @target_type is &DAMON_ADAPTIVE_TARGET.  @arbitrary_target is valid only if
- * @target_type is &DAMON_ARBITRARY_TARGET.
+ * @min_nr_regions, @max_nr_regions, @adaptive_targets and @schemes are valid
+ * only if @target_type is &DAMON_ADAPTIVE_TARGET.  @arbitrary_target is valid
+ * only if @target_type is &DAMON_ARBITRARY_TARGET.
  */
 struct damon_ctx {
 	unsigned long sample_interval;
@@ -235,6 +284,7 @@ struct damon_ctx {
 			unsigned long min_nr_regions;
 			unsigned long max_nr_regions;
 			struct list_head adaptive_targets;
+			struct list_head schemes;
 		};
 
 		void *arbitrary_target;	/* DAMON_ARBITRARY_TARGET */
@@ -259,6 +309,12 @@ struct damon_ctx {
 #define damon_for_each_target_safe(t, next, ctx)	\
 	list_for_each_entry_safe(t, next, &(ctx)->adaptive_targets, list)
 
+#define damon_for_each_scheme(s, ctx) \
+	list_for_each_entry(s, &(ctx)->schemes, list)
+
+#define damon_for_each_scheme_safe(s, next, ctx) \
+	list_for_each_entry_safe(s, next, &(ctx)->schemes, list)
+
 #ifdef CONFIG_DAMON
 
 struct damon_region *damon_new_region(unsigned long start, unsigned long end);
@@ -267,6 +323,14 @@ inline void damon_insert_region(struct damon_region *r,
 void damon_add_region(struct damon_region *r, struct damon_target *t);
 void damon_destroy_region(struct damon_region *r);
 
+struct damos *damon_new_scheme(
+		unsigned long min_sz_region, unsigned long max_sz_region,
+		unsigned int min_nr_accesses, unsigned int max_nr_accesses,
+		unsigned int min_age_region, unsigned int max_age_region,
+		enum damos_action action);
+void damon_add_scheme(struct damon_ctx *ctx, struct damos *s);
+void damon_destroy_scheme(struct damos *s);
+
 struct damon_target *damon_new_target(unsigned long id);
 void damon_add_target(struct damon_ctx *ctx, struct damon_target *t);
 void damon_free_target(struct damon_target *t);
@@ -280,6 +344,8 @@ int damon_set_targets(struct damon_ctx *ctx,
 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_schemes(struct damon_ctx *ctx,
+			struct damos **schemes, ssize_t nr_schemes);
 int damon_nr_running_ctxs(void);
 
 int damon_start(struct damon_ctx **ctxs, int nr_ctxs);
diff --git a/mm/damon/core.c b/mm/damon/core.c
index c4d4114a7545..a4d33970ba4c 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -81,6 +81,50 @@ void damon_destroy_region(struct damon_region *r)
 	damon_free_region(r);
 }
 
+struct damos *damon_new_scheme(
+		unsigned long min_sz_region, unsigned long max_sz_region,
+		unsigned int min_nr_accesses, unsigned int max_nr_accesses,
+		unsigned int min_age_region, unsigned int max_age_region,
+		enum damos_action action)
+{
+	struct damos *scheme;
+
+	scheme = kmalloc(sizeof(*scheme), GFP_KERNEL);
+	if (!scheme)
+		return NULL;
+	scheme->min_sz_region = min_sz_region;
+	scheme->max_sz_region = max_sz_region;
+	scheme->min_nr_accesses = min_nr_accesses;
+	scheme->max_nr_accesses = max_nr_accesses;
+	scheme->min_age_region = min_age_region;
+	scheme->max_age_region = max_age_region;
+	scheme->action = action;
+	INIT_LIST_HEAD(&scheme->list);
+
+	return scheme;
+}
+
+void damon_add_scheme(struct damon_ctx *ctx, struct damos *s)
+{
+	list_add_tail(&s->list, &ctx->schemes);
+}
+
+static void damon_del_scheme(struct damos *s)
+{
+	list_del(&s->list);
+}
+
+static void damon_free_scheme(struct damos *s)
+{
+	kfree(s);
+}
+
+void damon_destroy_scheme(struct damos *s)
+{
+	damon_del_scheme(s);
+	damon_free_scheme(s);
+}
+
 /*
  * Construct a damon_target struct
  *
@@ -159,6 +203,7 @@ struct damon_ctx *damon_new_ctx(enum damon_target_type type)
 		ctx->max_nr_regions = 1000;
 
 		INIT_LIST_HEAD(&ctx->adaptive_targets);
+		INIT_LIST_HEAD(&ctx->schemes);
 	}
 
 	return ctx;
@@ -167,10 +212,14 @@ struct damon_ctx *damon_new_ctx(enum damon_target_type type)
 void damon_destroy_ctx(struct damon_ctx *ctx)
 {
 	struct damon_target *t, *next_t;
+	struct damos *s, *next_s;
 
 	damon_for_each_target_safe(t, next_t, ctx)
 		damon_destroy_target(t);
 
+	damon_for_each_scheme_safe(s, next_s, ctx)
+		damon_destroy_scheme(s);
+
 	kfree(ctx);
 }
 
@@ -245,6 +294,30 @@ int damon_set_attrs(struct damon_ctx *ctx, unsigned long sample_int,
 	return 0;
 }
 
+/**
+ * damon_set_schemes() - Set data access monitoring based operation schemes.
+ * @ctx:	monitoring context
+ * @schemes:	array of the schemes
+ * @nr_schemes:	number of entries in @schemes
+ *
+ * This function should not be called while the kdamond of the context is
+ * running.
+ *
+ * Return: 0 if success, or negative error code otherwise.
+ */
+int damon_set_schemes(struct damon_ctx *ctx, struct damos **schemes,
+			ssize_t nr_schemes)
+{
+	struct damos *s, *next;
+	ssize_t i;
+
+	damon_for_each_scheme_safe(s, next, ctx)
+		damon_destroy_scheme(s);
+	for (i = 0; i < nr_schemes; i++)
+		damon_add_scheme(ctx, schemes[i]);
+	return 0;
+}
+
 /**
  * damon_nr_running_ctxs() - Return number of currently running contexts.
  */
@@ -448,6 +521,39 @@ static void kdamond_reset_aggregated(struct damon_ctx *c)
 	}
 }
 
+static void damon_do_apply_schemes(struct damon_ctx *c,
+				   struct damon_target *t,
+				   struct damon_region *r)
+{
+	struct damos *s;
+	unsigned long sz;
+
+	damon_for_each_scheme(s, c) {
+		sz = r->ar.end - r->ar.start;
+		if (sz < s->min_sz_region || s->max_sz_region < sz)
+			continue;
+		if (r->nr_accesses < s->min_nr_accesses ||
+				s->max_nr_accesses < r->nr_accesses)
+			continue;
+		if (r->age < s->min_age_region || s->max_age_region < r->age)
+			continue;
+		if (c->primitive.apply_scheme)
+			c->primitive.apply_scheme(c, t, r, s);
+		r->age = 0;
+	}
+}
+
+static void kdamond_apply_schemes(struct damon_ctx *c)
+{
+	struct damon_target *t;
+	struct damon_region *r;
+
+	damon_for_each_target(t, c) {
+		damon_for_each_region(r, t)
+			damon_do_apply_schemes(c, t, r);
+	}
+}
+
 #define sz_damon_region(r) (r->ar.end - r->ar.start)
 
 /*
@@ -689,6 +795,7 @@ static int kdamond_fn(void *data)
 					ctx->callback.after_aggregation(ctx))
 				set_kdamond_stop(ctx);
 			if (ctx->target_type != DAMON_ARBITRARY_TARGET) {
+				kdamond_apply_schemes(ctx);
 				kdamond_reset_aggregated(ctx);
 				kdamond_split_regions(ctx);
 			}
-- 
2.17.1

[RFC v15.1 3/8] mm/damon/vaddr: Support DAMON-based Operation Schemes

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit makes DAMON's default primitives for virtual address spaces
to support DAMON-based Operation Schemes (DAMOS) by implementing actions
application functions and registering it to the monitoring context.  The
implementation simply links 'madvise()' for related DAMOS actions.  That
is, 'madvise(MADV_WILLNEED)' is called for 'WILLNEED' DAMOS action and
similar for other actions ('COLD', 'PAGEOUT', 'HUGEPAGE', 'NOHUGEPAGE').

So, the kernel space DAMON users can now use the DAMON-based
optimizations with only small amount of code.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h |  2 ++
 mm/damon/vaddr.c      | 56 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index cfcd399da134..8988238cb29e 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -362,6 +362,8 @@ void damon_va_prepare_access_checks(struct damon_ctx *ctx);
 unsigned int damon_va_check_accesses(struct damon_ctx *ctx);
 bool damon_va_target_valid(void *t);
 void damon_va_cleanup(struct damon_ctx *ctx);
+int damon_va_apply_scheme(struct damon_ctx *context, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme);
 void damon_va_set_primitives(struct damon_ctx *ctx);
 
 #endif	/* CONFIG_DAMON_VADDR */
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index 8ee48a4abc17..ebf4720c057a 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -7,6 +7,7 @@
 
 #define pr_fmt(fmt) "damon-va: " fmt
 
+#include <asm-generic/mman-common.h>
 #include <linux/damon.h>
 #include <linux/mm.h>
 #include <linux/mmu_notifier.h>
@@ -572,6 +573,60 @@ void damon_va_cleanup(struct damon_ctx *ctx)
 	}
 }
 
+#ifndef CONFIG_ADVISE_SYSCALLS
+static int damos_madvise(struct damon_target *target, struct damon_region *r,
+			int behavior)
+{
+	return -EINVAL;
+}
+#else
+static int damos_madvise(struct damon_target *target, struct damon_region *r,
+			int behavior)
+{
+	struct mm_struct *mm;
+	int ret = -ENOMEM;
+
+	mm = damon_get_mm(target);
+	if (!mm)
+		goto out;
+
+	ret = do_madvise(mm, PAGE_ALIGN(r->ar.start),
+			PAGE_ALIGN(r->ar.end - r->ar.start), behavior);
+	mmput(mm);
+out:
+	return ret;
+}
+#endif	/* CONFIG_ADVISE_SYSCALLS */
+
+int damon_va_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
+		struct damon_region *r, struct damos *scheme)
+{
+	int madv_action;
+
+	switch (scheme->action) {
+	case DAMOS_WILLNEED:
+		madv_action = MADV_WILLNEED;
+		break;
+	case DAMOS_COLD:
+		madv_action = MADV_COLD;
+		break;
+	case DAMOS_PAGEOUT:
+		madv_action = MADV_PAGEOUT;
+		break;
+	case DAMOS_HUGEPAGE:
+		madv_action = MADV_HUGEPAGE;
+		break;
+	case DAMOS_NOHUGEPAGE:
+		madv_action = MADV_NOHUGEPAGE;
+		break;
+	default:
+		pr_warn("Wrong action %d\n", scheme->action);
+		return -EINVAL;
+	}
+
+	return damos_madvise(t, r, madv_action);
+}
+
 void damon_va_set_primitives(struct damon_ctx *ctx)
 {
 	ctx->primitive.init_target_regions = damon_va_init_regions;
@@ -581,6 +636,7 @@ void damon_va_set_primitives(struct damon_ctx *ctx)
 	ctx->primitive.reset_aggregated = NULL;
 	ctx->primitive.target_valid = damon_va_target_valid;
 	ctx->primitive.cleanup = damon_va_cleanup;
+	ctx->primitive.apply_scheme = damon_va_apply_scheme;
 }
 
 #include "vaddr-test.h"
-- 
2.17.1

[RFC v15.1 4/8] mm/damon/dbgfs: Support DAMON-based Operation Schemes

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit makes 'damon-dbgfs' to support the data access monitoring
oriented memory management schemes.  Users can read and update the
schemes using ``<debugfs>/damon/schemes`` file.  The format is::

    <min/max size> <min/max access frequency> <min/max age> <action>

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 mm/damon/dbgfs.c | 169 +++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 165 insertions(+), 4 deletions(-)

diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 7380c6502f3d..10ce8e8786cb 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -219,6 +219,159 @@ static ssize_t dbgfs_record_write(struct file *file,
 	return ret;
 }
 
+static ssize_t sprint_schemes(struct damon_ctx *c, char *buf, ssize_t len)
+{
+	struct damos *s;
+	int written = 0;
+	int rc;
+
+	damon_for_each_scheme(s, c) {
+		rc = scnprintf(&buf[written], len - written,
+				"%lu %lu %u %u %u %u %d\n",
+				s->min_sz_region, s->max_sz_region,
+				s->min_nr_accesses, s->max_nr_accesses,
+				s->min_age_region, s->max_age_region,
+				s->action);
+		if (!rc)
+			return -ENOMEM;
+
+		written += rc;
+	}
+	return written;
+}
+
+static ssize_t dbgfs_schemes_read(struct file *file, char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = file->private_data;
+	char *kbuf;
+	ssize_t len;
+
+	kbuf = kmalloc(count, GFP_KERNEL);
+	if (!kbuf)
+		return -ENOMEM;
+
+	mutex_lock(&ctx->kdamond_lock);
+	len = sprint_schemes(ctx, kbuf, count);
+	mutex_unlock(&ctx->kdamond_lock);
+	if (len < 0)
+		goto out;
+	len = simple_read_from_buffer(buf, count, ppos, kbuf, len);
+
+out:
+	kfree(kbuf);
+	return len;
+}
+
+static void free_schemes_arr(struct damos **schemes, ssize_t nr_schemes)
+{
+	ssize_t i;
+
+	for (i = 0; i < nr_schemes; i++)
+		kfree(schemes[i]);
+	kfree(schemes);
+}
+
+static bool damos_action_valid(int action)
+{
+	switch (action) {
+	case DAMOS_WILLNEED:
+	case DAMOS_COLD:
+	case DAMOS_PAGEOUT:
+	case DAMOS_HUGEPAGE:
+	case DAMOS_NOHUGEPAGE:
+		return true;
+	default:
+		return false;
+	}
+}
+
+/*
+ * Converts a string into an array of struct damos pointers
+ *
+ * Returns an array of struct damos pointers that converted if the conversion
+ * success, or NULL otherwise.
+ */
+static struct damos **str_to_schemes(const char *str, ssize_t len,
+				ssize_t *nr_schemes)
+{
+	struct damos *scheme, **schemes;
+	const int max_nr_schemes = 256;
+	int pos = 0, parsed, ret;
+	unsigned long min_sz, max_sz;
+	unsigned int min_nr_a, max_nr_a, min_age, max_age;
+	unsigned int action;
+
+	schemes = kmalloc_array(max_nr_schemes, sizeof(scheme),
+			GFP_KERNEL);
+	if (!schemes)
+		return NULL;
+
+	*nr_schemes = 0;
+	while (pos < len && *nr_schemes < max_nr_schemes) {
+		ret = sscanf(&str[pos], "%lu %lu %u %u %u %u %u%n",
+				&min_sz, &max_sz, &min_nr_a, &max_nr_a,
+				&min_age, &max_age, &action, &parsed);
+		if (ret != 7)
+			break;
+		if (!damos_action_valid(action)) {
+			pr_err("wrong action %d\n", action);
+			goto fail;
+		}
+
+		pos += parsed;
+		scheme = damon_new_scheme(min_sz, max_sz, min_nr_a, max_nr_a,
+				min_age, max_age, action);
+		if (!scheme)
+			goto fail;
+
+		schemes[*nr_schemes] = scheme;
+		*nr_schemes += 1;
+	}
+	return schemes;
+fail:
+	free_schemes_arr(schemes, *nr_schemes);
+	return NULL;
+}
+
+static ssize_t dbgfs_schemes_write(struct file *file, const char __user *buf,
+		size_t count, loff_t *ppos)
+{
+	struct damon_ctx *ctx = file->private_data;
+	char *kbuf;
+	struct damos **schemes;
+	ssize_t nr_schemes = 0, ret = count;
+	int err;
+
+	kbuf = user_input_str(buf, count, ppos);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	schemes = str_to_schemes(kbuf, ret, &nr_schemes);
+	if (!schemes) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	mutex_lock(&ctx->kdamond_lock);
+	if (ctx->kdamond) {
+		ret = -EBUSY;
+		goto unlock_out;
+	}
+
+	err = damon_set_schemes(ctx, schemes, nr_schemes);
+	if (err)
+		ret = err;
+	else
+		nr_schemes = 0;
+unlock_out:
+	mutex_unlock(&ctx->kdamond_lock);
+	free_schemes_arr(schemes, nr_schemes);
+out:
+	kfree(kbuf);
+	return ret;
+}
+
 #define targetid_is_pid(ctx)	\
 	(ctx->primitive.target_valid == damon_va_target_valid)
 
@@ -385,6 +538,13 @@ static const struct file_operations record_fops = {
 	.write = dbgfs_record_write,
 };
 
+static const struct file_operations schemes_fops = {
+	.owner = THIS_MODULE,
+	.open = damon_dbgfs_open,
+	.read = dbgfs_schemes_read,
+	.write = dbgfs_schemes_write,
+};
+
 static const struct file_operations target_ids_fops = {
 	.owner = THIS_MODULE,
 	.open = damon_dbgfs_open,
@@ -400,10 +560,11 @@ static const struct file_operations kdamond_pid_fops = {
 
 static int dbgfs_fill_ctx_dir(struct dentry *dir, struct damon_ctx *ctx)
 {
-	const char * const file_names[] = {"attrs", "record", "target_ids",
-		"kdamond_pid"};
-	const struct file_operations *fops[] = {&attrs_fops, &record_fops,
-		&target_ids_fops, &kdamond_pid_fops};
+	const char * const file_names[] = {"attrs", "record", "schemes",
+		"target_ids", "kdamond_pid"};
+	const struct file_operations *fops[] = {&attrs_fops,
+		&record_fops, &schemes_fops, &target_ids_fops,
+		&kdamond_pid_fops};
 	int i;
 
 	for (i = 0; i < ARRAY_SIZE(file_names); i++) {
-- 
2.17.1

[RFC v15.1 5/8] mm/damon/schemes: Implement statistics feature

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

To tune the DAMON-based operation schemes, knowing how many and how
large regions are affected by each of the schemes will be helful.  Those
stats could be used for not only the tuning, but also monitoring of the
working set size and the number of regions, if the scheme does not
change the program behavior too much.

For the reason, this commit implements the statistics for the schemes.
The total number and size of the regions that each scheme is applied are
exported to users via '->stat_count' and '->stat_sz' of 'struct damos'.
Admins can also check the number by reading 'schemes' debugfs file.  The
last two integers now represents the stats.  To allow collecting the
stats without changing the program behavior, this commit also adds new
scheme action, 'DAMOS_STAT'.  Note that 'DAMOS_STAT' is not only making
no memory operation actions, but also does not reset the age of regions.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 include/linux/damon.h | 10 +++++++++-
 mm/damon/core.c       |  7 ++++++-
 mm/damon/dbgfs.c      |  5 +++--
 mm/damon/vaddr.c      |  2 ++
 4 files changed, 20 insertions(+), 4 deletions(-)

diff --git a/include/linux/damon.h b/include/linux/damon.h
index 8988238cb29e..ed7e86207e53 100644
--- a/include/linux/damon.h
+++ b/include/linux/damon.h
@@ -76,6 +76,7 @@ struct damon_target {
  * @DAMOS_PAGEOUT:	Call ``madvise()`` for the region with MADV_PAGEOUT.
  * @DAMOS_HUGEPAGE:	Call ``madvise()`` for the region with MADV_HUGEPAGE.
  * @DAMOS_NOHUGEPAGE:	Call ``madvise()`` for the region with MADV_NOHUGEPAGE.
+ * @DAMOS_STAT:		Do nothing but count the stat.
  */
 enum damos_action {
 	DAMOS_WILLNEED,
@@ -83,6 +84,7 @@ enum damos_action {
 	DAMOS_PAGEOUT,
 	DAMOS_HUGEPAGE,
 	DAMOS_NOHUGEPAGE,
+	DAMOS_STAT,		/* Do nothing but only record the stat */
 };
 
 /**
@@ -94,9 +96,13 @@ enum damos_action {
  * @min_age_region:	Minimum age of target regions.
  * @max_age_region:	Maximum age of target regions.
  * @action:		&damo_action to be applied to the target regions.
+ * @stat_count:		Total number of regions that this scheme is applied.
+ * @stat_sz:		Total size of regions that this scheme is applied.
  * @list:		List head for siblings.
  *
- * Note that both the minimums and the maximums are inclusive.
+ * For each aggregation interval, DAMON applies @action to monitoring target
+ * regions fit in the condition and updates the statistics.  Note that both
+ * the minimums and the maximums are inclusive.
  */
 struct damos {
 	unsigned long min_sz_region;
@@ -106,6 +112,8 @@ struct damos {
 	unsigned int min_age_region;
 	unsigned int max_age_region;
 	enum damos_action action;
+	unsigned long stat_count;
+	unsigned long stat_sz;
 	struct list_head list;
 };
 
diff --git a/mm/damon/core.c b/mm/damon/core.c
index a4d33970ba4c..e339b79b23c7 100644
--- a/mm/damon/core.c
+++ b/mm/damon/core.c
@@ -99,6 +99,8 @@ struct damos *damon_new_scheme(
 	scheme->min_age_region = min_age_region;
 	scheme->max_age_region = max_age_region;
 	scheme->action = action;
+	scheme->stat_count = 0;
+	scheme->stat_sz = 0;
 	INIT_LIST_HEAD(&scheme->list);
 
 	return scheme;
@@ -537,9 +539,12 @@ static void damon_do_apply_schemes(struct damon_ctx *c,
 			continue;
 		if (r->age < s->min_age_region || s->max_age_region < r->age)
 			continue;
+		s->stat_count++;
+		s->stat_sz += sz;
 		if (c->primitive.apply_scheme)
 			c->primitive.apply_scheme(c, t, r, s);
-		r->age = 0;
+		if (s->action != DAMOS_STAT)
+			r->age = 0;
 	}
 }
 
diff --git a/mm/damon/dbgfs.c b/mm/damon/dbgfs.c
index 10ce8e8786cb..06295c986dc3 100644
--- a/mm/damon/dbgfs.c
+++ b/mm/damon/dbgfs.c
@@ -227,11 +227,11 @@ static ssize_t sprint_schemes(struct damon_ctx *c, char *buf, ssize_t len)
 
 	damon_for_each_scheme(s, c) {
 		rc = scnprintf(&buf[written], len - written,
-				"%lu %lu %u %u %u %u %d\n",
+				"%lu %lu %u %u %u %u %d %lu %lu\n",
 				s->min_sz_region, s->max_sz_region,
 				s->min_nr_accesses, s->max_nr_accesses,
 				s->min_age_region, s->max_age_region,
-				s->action);
+				s->action, s->stat_count, s->stat_sz);
 		if (!rc)
 			return -ENOMEM;
 
@@ -280,6 +280,7 @@ static bool damos_action_valid(int action)
 	case DAMOS_PAGEOUT:
 	case DAMOS_HUGEPAGE:
 	case DAMOS_NOHUGEPAGE:
+	case DAMOS_STAT:
 		return true;
 	default:
 		return false;
diff --git a/mm/damon/vaddr.c b/mm/damon/vaddr.c
index ebf4720c057a..2075f07f728b 100644
--- a/mm/damon/vaddr.c
+++ b/mm/damon/vaddr.c
@@ -619,6 +619,8 @@ int damon_va_apply_scheme(struct damon_ctx *ctx, struct damon_target *t,
 	case DAMOS_NOHUGEPAGE:
 		madv_action = MADV_NOHUGEPAGE;
 		break;
+	case DAMOS_STAT:
+		return 0;
 	default:
 		pr_warn("Wrong action %d\n", scheme->action);
 		return -EINVAL;
-- 
2.17.1

[RFC v15.1 6/8] selftests/damon: Add 'schemes' debugfs tests

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit adds simple selftets for 'schemes' debugfs file of DAMON.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 .../testing/selftests/damon/debugfs_attrs.sh  | 29 +++++++++++++++++++
 1 file changed, 29 insertions(+)

diff --git a/tools/testing/selftests/damon/debugfs_attrs.sh b/tools/testing/selftests/damon/debugfs_attrs.sh
index c75557e8ba58..61fd3e5598e9 100755
--- a/tools/testing/selftests/damon/debugfs_attrs.sh
+++ b/tools/testing/selftests/damon/debugfs_attrs.sh
@@ -97,6 +97,35 @@ fi
 
 echo $ORIG_CONTENT > $file
 
+# Test schemes file
+file="$DBGFS/schemes"
+
+ORIG_CONTENT=$(cat $file)
+echo "1 2 3 4 5 6 3" > $file
+if [ $? -ne 0 ]
+then
+	echo "$file write fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo "1 2
+3 4 5 6 3" > $file
+if [ $? -eq 0 ]
+then
+	echo "$file multi line write success (expected fail)"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
+echo > $file
+if [ $? -ne 0 ]
+then
+	echo "$file empty string writing fail"
+	echo $ORIG_CONTENT > $file
+	exit 1
+fi
+
 # Test target_ids file
 file="$DBGFS/target_ids"
 
-- 
2.17.1

[RFC v15.1 7/8] tools/damon: Support more human friendly 'schemes' control

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit implements 'schemes' subcommand of the damon userspace tool.
It can be used to describe and apply the data access monitoring-based
operation schemes in more human friendly fashion.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 tools/damon/_convert_damos.py | 141 ++++++++++++++++++++++++++++++++++
 tools/damon/_damon.py         |  28 +++++--
 tools/damon/damo              |   7 ++
 tools/damon/schemes.py        | 110 ++++++++++++++++++++++++++
 4 files changed, 280 insertions(+), 6 deletions(-)
 create mode 100755 tools/damon/_convert_damos.py
 create mode 100644 tools/damon/schemes.py

diff --git a/tools/damon/_convert_damos.py b/tools/damon/_convert_damos.py
new file mode 100755
index 000000000000..0fd84b3701c9
--- /dev/null
+++ b/tools/damon/_convert_damos.py
@@ -0,0 +1,141 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Change human readable data access monitoring-based operation schemes to the low
+level input for the '<debugfs>/damon/schemes' file.  Below is an example of the
+schemes written in the human readable format:
+
+    # format is:
+    # <min/max size> <min/max frequency (0-100)> <min/max age> <action>
+    #
+    # B/K/M/G/T for Bytes/KiB/MiB/GiB/TiB
+    # us/ms/s/m/h/d for micro-seconds/milli-seconds/seconds/minutes/hours/days
+    # 'min/max' for possible min/max value.
+
+    # if a region keeps a high access frequency for >=100ms, put the region on
+    # the head of the LRU list (call madvise() with MADV_WILLNEED).
+    min    max      80      max     100ms   max willneed
+
+    # if a region keeps a low access frequency for >=200ms and <=one hour, put
+    # the region on the tail of the LRU list (call madvise() with MADV_COLD).
+    min     max     10      20      200ms   1h  cold
+
+    # if a region keeps a very low access frequency for >=60 seconds, swap out
+    # the region immediately (call madvise() with MADV_PAGEOUT).
+    min     max     0       10      60s     max pageout
+
+    # if a region of a size >=2MiB keeps a very high access frequency for
+    # >=100ms, let the region to use huge pages (call madvise() with
+    # MADV_HUGEPAGE).
+    2M      max     90      100     100ms   max hugepage
+
+    # If a regions of a size >=2MiB keeps small access frequency for >=100ms,
+    # avoid the region using huge pages (call madvise() with MADV_NOHUGEPAGE).
+    2M      max     0       25      100ms   max nohugepage
+"""
+
+import argparse
+import platform
+
+uint_max = 2**32 - 1
+ulong_max = 2**64 - 1
+if platform.architecture()[0] != '64bit':
+    ulong_max = 2**32 - 1
+
+unit_to_bytes = {'B': 1, 'K': 1024, 'M': 1024 * 1024, 'G': 1024 * 1024 * 1024,
+        'T': 1024 * 1024 * 1024 * 1024}
+
+def text_to_bytes(txt):
+    if txt == 'min':
+        return 0
+    if txt == 'max':
+        return ulong_max
+
+    unit = txt[-1]
+    number = float(txt[:-1])
+    return int(number * unit_to_bytes[unit])
+
+unit_to_usecs = {'us': 1, 'ms': 1000, 's': 1000 * 1000, 'm': 60 * 1000 * 1000,
+        'h': 60 * 60 * 1000 * 1000, 'd': 24 * 60 * 60 * 1000 * 1000}
+
+def text_to_aggr_intervals(txt, aggr_interval):
+    if txt == 'min':
+        return 0
+    if txt == 'max':
+        return uint_max
+
+    unit = txt[-2:]
+    if unit in ['us', 'ms']:
+        number = float(txt[:-2])
+    else:
+        unit = txt[-1]
+        number = float(txt[:-1])
+    return int(number * unit_to_usecs[unit]) / aggr_interval
+
+damos_action_to_int = {'DAMOS_WILLNEED': 0, 'DAMOS_COLD': 1,
+        'DAMOS_PAGEOUT': 2, 'DAMOS_HUGEPAGE': 3, 'DAMOS_NOHUGEPAGE': 4,
+        'DAMOS_STAT': 5}
+
+def text_to_damos_action(txt):
+    return damos_action_to_int['DAMOS_' + txt.upper()]
+
+def text_to_nr_accesses(txt, max_nr_accesses):
+    if txt == 'min':
+        return 0
+    if txt == 'max':
+        return max_nr_accesses
+
+    return int(float(txt) * max_nr_accesses / 100)
+
+def debugfs_scheme(line, sample_interval, aggr_interval):
+    fields = line.split()
+    if len(fields) != 7:
+        print('wrong input line: %s' % line)
+        exit(1)
+
+    limit_nr_accesses = aggr_interval / sample_interval
+    try:
+        min_sz = text_to_bytes(fields[0])
+        max_sz = text_to_bytes(fields[1])
+        min_nr_accesses = text_to_nr_accesses(fields[2], limit_nr_accesses)
+        max_nr_accesses = text_to_nr_accesses(fields[3], limit_nr_accesses)
+        min_age = text_to_aggr_intervals(fields[4], aggr_interval)
+        max_age = text_to_aggr_intervals(fields[5], aggr_interval)
+        action = text_to_damos_action(fields[6])
+    except:
+        print('wrong input field')
+        raise
+    return '%d\t%d\t%d\t%d\t%d\t%d\t%d' % (min_sz, max_sz, min_nr_accesses,
+            max_nr_accesses, min_age, max_age, action)
+
+def convert(schemes_file, sample_interval, aggr_interval):
+    lines = []
+    with open(schemes_file, 'r') as f:
+        for line in f:
+            if line.startswith('#'):
+                continue
+            line = line.strip()
+            if line == '':
+                continue
+            lines.append(debugfs_scheme(line, sample_interval, aggr_interval))
+    return '\n'.join(lines)
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('input', metavar='<file>',
+            help='input file describing the schemes')
+    parser.add_argument('-s', '--sample', metavar='<interval>', type=int,
+            default=5000, help='sampling interval (us)')
+    parser.add_argument('-a', '--aggr', metavar='<interval>', type=int,
+            default=100000, help='aggregation interval (us)')
+    args = parser.parse_args()
+
+    schemes_file = args.input
+    sample_interval = args.sample
+    aggr_interval = args.aggr
+
+    print(convert(schemes_file, sample_interval, aggr_interval))
+
+if __name__ == '__main__':
+    main()
diff --git a/tools/damon/_damon.py b/tools/damon/_damon.py
index 1f6a292e8c25..a4f6c03c23e4 100644
--- a/tools/damon/_damon.py
+++ b/tools/damon/_damon.py
@@ -10,6 +10,7 @@ import subprocess
 
 debugfs_attrs = None
 debugfs_record = None
+debugfs_schemes = None
 debugfs_target_ids = None
 debugfs_monitor_on = None
 
@@ -33,8 +34,9 @@ class Attrs:
     max_nr_regions = None
     rbuf_len = None
     rfile_path = None
+    schemes = None
 
-    def __init__(self, s, a, r, n, x, l, f):
+    def __init__(self, s, a, r, n, x, l, f, c):
         self.sample_interval = s
         self.aggr_interval = a
         self.regions_update_interval = r
@@ -42,12 +44,13 @@ class Attrs:
         self.max_nr_regions = x
         self.rbuf_len = l
         self.rfile_path = f
+        self.schemes = c
 
     def __str__(self):
-        return "%s %s %s %s %s %s %s" % (self.sample_interval,
+        return "%s %s %s %s %s %s %s\n%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)
+                self.rfile_path, self.schemes)
 
     def attr_str(self):
         return "%s %s %s %s %s " % (self.sample_interval, self.aggr_interval,
@@ -66,6 +69,9 @@ class Attrs:
             debugfs_record), shell=True, executable='/bin/bash')
         if ret:
             return ret
+        return subprocess.call('echo %s > %s' % (
+            self.schemes.replace('\n', ' '), debugfs_schemes), shell=True,
+            executable='/bin/bash')
 
 def current_attrs():
     with open(debugfs_attrs, 'r') as f:
@@ -77,17 +83,26 @@ def current_attrs():
     attrs.append(int(rattrs[0]))
     attrs.append(rattrs[1])
 
+    with open(debugfs_schemes, 'r') as f:
+        schemes = f.read()
+
+    # The last two fields in each line are statistics.  Remove those.
+    schemes = [' '.join(x.split()[:-2]) for x in schemes.strip().split('\n')]
+    attrs.append('\n'.join(schemes))
+
     return Attrs(*attrs)
 
 def chk_update_debugfs(debugfs):
     global debugfs_attrs
     global debugfs_record
+    global debugfs_schemes
     global debugfs_target_ids
     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_schemes = os.path.join(debugfs_damon, 'schemes')
     debugfs_target_ids = os.path.join(debugfs_damon, 'target_ids')
     debugfs_monitor_on = os.path.join(debugfs_damon, 'monitor_on')
 
@@ -95,8 +110,8 @@ def chk_update_debugfs(debugfs):
         print("damon debugfs dir (%s) not found", debugfs_damon)
         exit(1)
 
-    for f in [debugfs_attrs, debugfs_record, debugfs_target_ids,
-            debugfs_monitor_on]:
+    for f in [debugfs_attrs, debugfs_record, debugfs_schemes,
+            debugfs_target_ids, debugfs_monitor_on]:
         if not os.path.isfile(f):
             print("damon debugfs file (%s) not found" % f)
             exit(1)
@@ -112,8 +127,9 @@ def cmd_args_to_attrs(args):
     if not os.path.isabs(args.out):
         args.out = os.path.join(os.getcwd(), args.out)
     rfile_path = args.out
+    schemes = args.schemes
     return Attrs(sample_interval, aggr_interval, regions_update_interval,
-            min_nr_regions, max_nr_regions, rbuf_len, rfile_path)
+            min_nr_regions, max_nr_regions, rbuf_len, rfile_path, schemes)
 
 def set_attrs_argparser(parser):
     parser.add_argument('-d', '--debugfs', metavar='<debugfs>', type=str,
diff --git a/tools/damon/damo b/tools/damon/damo
index 58e1099ae5fc..ce7180069bef 100755
--- a/tools/damon/damo
+++ b/tools/damon/damo
@@ -5,6 +5,7 @@ import argparse
 
 import record
 import report
+import schemes
 
 class SubCmdHelpFormatter(argparse.RawDescriptionHelpFormatter):
     def _format_action(self, action):
@@ -25,6 +26,10 @@ parser_record = subparser.add_parser('record',
         help='record data accesses of the given target processes')
 record.set_argparser(parser_record)
 
+parser_schemes = subparser.add_parser('schemes',
+        help='apply operation schemes to the given target process')
+schemes.set_argparser(parser_schemes)
+
 parser_report = subparser.add_parser('report',
         help='report the recorded data accesses in the specified form')
 report.set_argparser(parser_report)
@@ -33,5 +38,7 @@ args = parser.parse_args()
 
 if args.command == 'record':
     record.main(args)
+elif args.command == 'schemes':
+    schemes.main(args)
 elif args.command == 'report':
     report.main(args)
diff --git a/tools/damon/schemes.py b/tools/damon/schemes.py
new file mode 100644
index 000000000000..9095835f6133
--- /dev/null
+++ b/tools/damon/schemes.py
@@ -0,0 +1,110 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""
+Apply given operation schemes to the target process.
+"""
+
+import argparse
+import os
+import signal
+import subprocess
+import time
+
+import _convert_damos
+import _damon
+
+def run_damon(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()))
+    for line in attrs.schemes.split('\n'):
+        print('# scheme: %s' % line)
+    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():
+        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():
+            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('-c', '--schemes', metavar='<file>', type=str,
+            default='damon.schemes',
+            help='data access monitoring-based operation schemes')
+
+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.rbuf = 0
+    args.out = 'null'
+    args.schemes = _convert_damos.convert(args.schemes, args.sample, args.aggr)
+    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'):
+        run_damon(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)
+        run_damon(target, False, new_attrs, orig_attrs)
+
+if __name__ == '__main__':
+    main()
-- 
2.17.1

[RFC v15.1 8/8] Docs/admin-guide/mm/damon: Document DAMON-based Operation Schemes

[SeongJae Park]

From: SeongJae Park <sjpark@amazon.de>

This commit add description of DAMON-based operation schemes in the
DAMON documents.

Signed-off-by: SeongJae Park <sjpark@amazon.de>
---
 Documentation/admin-guide/mm/damon/guide.rst |  41 ++++++-
 Documentation/admin-guide/mm/damon/start.rst |  11 ++
 Documentation/admin-guide/mm/damon/usage.rst | 109 ++++++++++++++++++-
 Documentation/vm/damon/index.rst             |   1 -
 4 files changed, 156 insertions(+), 6 deletions(-)

diff --git a/Documentation/admin-guide/mm/damon/guide.rst b/Documentation/admin-guide/mm/damon/guide.rst
index c51fb843efaa..1f9aa2ebbdb6 100644
--- a/Documentation/admin-guide/mm/damon/guide.rst
+++ b/Documentation/admin-guide/mm/damon/guide.rst
@@ -53,6 +53,11 @@ heats``.  If it shows a simple pattern consists of a small number of memory
 regions having high contrast of access temperature, you could consider manual
 `Program Modification`_.
 
+If the access pattern is very frequently changing so that you cannot figure out
+what is the performance important region using your human eye, `Automated
+DAMON-based Memory Operations`_ might help the case owing to its machine-level
+microscope view.
+
 If you still want to absorb more benefits, you should develop `Personalized
 DAMON Application`_ for your special case.
 
@@ -120,6 +125,36 @@ shows the visualized access patterns of streamcluster workload in PARSEC3
 benchmark suite.  We can easily identify the 100 MiB sized hot object.
 
 
+Automated DAMON-based Memory Operations
+---------------------------------------
+
+Though `Manual Program Optimization` works well in many cases and DAMON can
+help it, modifying the source code is not a good option in many cases.  First
+of all, the source code could be too old or unavailable.  And, many workloads
+will have complex data access patterns that even hard to distinguish hot memory
+objects and cold memory objects with the human eye.  Finding the mapping from
+the visualized access pattern to the source code and injecting the hinting
+system calls inside the code will also be quite challenging.
+
+By using DAMON-based operation schemes (DAMOS) via ``damo schemes``, you will
+be able to easily optimize your workload in such a case.  Our example schemes
+called 'efficient THP' and 'proactive reclamation' achieved significant speedup
+and memory space saves against 25 realistic workloads [2]_.
+
+That said, note that you need careful tune of the schemes (e.g., target region
+size and age) and monitoring attributes for the successful use of this
+approach.  Because the optimal values of the parameters will be dependent on
+each system and workload, misconfiguring the parameters could result in worse
+memory management.
+
+For the tuning, you could measure the performance metrics such as IPC, TLB
+misses, and swap in/out events and adjusts the parameters based on their
+changes.  The total number and the total size of the regions that each scheme
+is applied, which are provided via the debugfs interface and the programming
+interface can also be useful.  Writing a program automating this optimal
+parameter could be an option.
+
+
 Personalized DAMON Application
 ------------------------------
 
@@ -146,9 +181,9 @@ Referencing previously done successful practices could help you getting the
 sense for this kind of optimizations.  There is an academic paper [1]_
 reporting the visualized access pattern and manual `Program
 Modification`_ results for a number of realistic workloads.  You can also get
-the visualized access patterns [3]_ [4]_ [5]_ and automated DAMON-based memory
-operations results for other realistic workloads that collected with latest
-version of DAMON [2]_ .
+the visualized access patterns [3]_ [4]_ [5]_ and
+`Automated DAMON-based Memory Operations`_ results for other realistic
+workloads that collected with latest version of DAMON [2]_ .
 
 .. [1] https://dl.acm.org/doi/10.1145/3366626.3368125
 .. [2] https://damonitor.github.io/test/result/perf/latest/html/
diff --git a/Documentation/admin-guide/mm/damon/start.rst b/Documentation/admin-guide/mm/damon/start.rst
index deed2ea2321e..35cf4e4ca6aa 100644
--- a/Documentation/admin-guide/mm/damon/start.rst
+++ b/Documentation/admin-guide/mm/damon/start.rst
@@ -90,6 +90,17 @@ image files. ::
 You can show the images in a web page [1]_ .  Those made with other realistic
 workloads are also available [2]_ [3]_ [4]_.
 
+
+Data Access Pattern Aware Memory Management
+===========================================
+
+Below three commands make every memory region of size >=4K that doesn't
+accessed for >=60 seconds in your workload to be swapped out. ::
+
+    $ echo "#min-size max-size min-acc max-acc min-age max-age action" > scheme
+    $ echo "4K        max      0       0       60s     max     pageout" >> scheme
+    $ damo schemes -c my_thp_scheme <pid of your workload>
+
 .. [1] https://damonitor.github.io/doc/html/v17/admin-guide/mm/damon/start.html#visualizing-recorded-patterns
 .. [2] https://damonitor.github.io/test/result/visual/latest/rec.heatmap.1.png.html
 .. [3] https://damonitor.github.io/test/result/visual/latest/rec.wss_sz.png.html
diff --git a/Documentation/admin-guide/mm/damon/usage.rst b/Documentation/admin-guide/mm/damon/usage.rst
index a6606d27a559..96278227f925 100644
--- a/Documentation/admin-guide/mm/damon/usage.rst
+++ b/Documentation/admin-guide/mm/damon/usage.rst
@@ -219,11 +219,70 @@ Similar to that of ``heats --heatmap``, it also supports 'gnuplot' based simple
 visualization of the distribution via ``--plot`` option.
 
 
+DAMON-based Operation Schemes
+-----------------------------
+
+The ``schemes`` subcommand allows users to do DAMON-based memory management
+optimizations in a few seconds.  Similar to ``record``, it receives monitoring
+attributes and target.  However, in addition to those, ``schemes`` receives
+data access pattern-based memory operation schemes, which describes what memory
+operation action should be applied to memory regions showing specific data
+access pattern.  Then, it starts the data access monitoring and automatically
+applies the schemes to the targets.
+
+The operation schemes should be saved in a text file in below format and passed
+to ``schemes`` subcommand via ``--schemes`` option. ::
+
+    min-size max-size min-acc max-acc min-age max-age action
+
+The format also supports comments, several units for size and age of regions,
+and human readable action names.  Currently supported operation actions are
+``willneed``, ``cold``, ``pageout``, ``hugepage`` and ``nohugepage``.  Each of
+the actions works same to the madvise() system call hints having the name.
+Please also note that the range is inclusive (closed interval), and ``0`` for
+max values means infinite. Below example schemes are possible. ::
+
+    # format is:
+    # <min/max size> <min/max frequency (0-100)> <min/max age> <action>
+    #
+    # B/K/M/G/T for Bytes/KiB/MiB/GiB/TiB
+    # us/ms/s/m/h/d for micro-seconds/milli-seconds/seconds/minutes/hours/days
+    # 'min/max' for possible min/max value.
+
+    # if a region keeps a high access frequency for >=100ms, put the region on
+    # the head of the LRU list (call madvise() with MADV_WILLNEED).
+    min    max      80      max     100ms   max willneed
+
+    # if a region keeps a low access frequency for >=200ms and <=one hour, put
+    # the region on the tail of the LRU list (call madvise() with MADV_COLD).
+    min     max     10      20      200ms   1h  cold
+
+    # if a region keeps a very low access frequency for >=60 seconds, swap out
+    # the region immediately (call madvise() with MADV_PAGEOUT).
+    min     max     0       10      60s     max pageout
+
+    # if a region of a size >=2MiB keeps a very high access frequency for
+    # >=100ms, let the region to use huge pages (call madvise() with
+    # MADV_HUGEPAGE).
+    2M      max     90      100     100ms   max hugepage
+
+    # If a regions of a size >=2MiB keeps small access frequency for >=100ms,
+    # avoid the region using huge pages (call madvise() with MADV_NOHUGEPAGE).
+    2M      max     0       25      100ms   max nohugepage
+
+For example, you can make a running process named 'foo' to use huge pages for
+memory regions keeping 2MB or larger size and having very high access frequency
+for at least 100 milliseconds using below commands::
+
+    $ echo "2M max    90 max    100ms max    hugepage" > my_thp_scheme
+    $ ./damo schemes --schemes my_thp_scheme `pidof foo`
+
+
 debugfs Interface
 =================
 
-DAMON exports four files, ``attrs``, ``target_ids``, ``record``, and
-``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
+DAMON exports five files, ``attrs``, ``target_ids``, ``record``, ``schemes``
+and ``monitor_on`` under its debugfs directory, ``<debugfs>/damon/``.
 
 
 Attributes
@@ -280,6 +339,52 @@ saved in ``/damon.data``. ::
 The recording can be disabled by setting the buffer size zero.
 
 
+Schemes
+-------
+
+For usual DAMON-based data access aware memory management optimizations, users
+would simply want the system to apply a memory management action to a memory
+region of a specific size having a specific access frequency for a specific
+time.  DAMON receives such formalized operation schemes from the user and
+applies those to the target processes.  It also counts the total number and
+size of regions that each scheme is applied.  This statistics can be used for
+online analysis or tuning of the schemes.
+
+Users can get and set the schemes by reading from and writing to ``schemes``
+debugfs file.  Reading the file also shows the statistics of each scheme.  To
+the file, each of the schemes should be represented in each line in below form:
+
+    min-size max-size min-acc max-acc min-age max-age action
+
+Note that the ranges are closed interval.  Bytes for the size of regions
+(``min-size`` and ``max-size``), number of monitored accesses per aggregate
+interval for access frequency (``min-acc`` and ``max-acc``), number of
+aggregate intervals for the age of regions (``min-age`` and ``max-age``), and a
+predefined integer for memory management actions should be used.  The supported
+numbers and their meanings are as below.
+
+ - 0: Call ``madvise()`` for the region with ``MADV_WILLNEED``
+ - 1: Call ``madvise()`` for the region with ``MADV_COLD``
+ - 2: Call ``madvise()`` for the region with ``MADV_PAGEOUT``
+ - 3: Call ``madvise()`` for the region with ``MADV_HUGEPAGE``
+ - 4: Call ``madvise()`` for the region with ``MADV_NOHUGEPAGE``
+ - 5: Do nothing but count the statistics
+
+You can disable schemes by simply writing an empty string to the file.  For
+example, below commands applies a scheme saying "If a memory region of size in
+[4KiB, 8KiB] is showing accesses per aggregate interval in [0, 5] for aggregate
+interval in [10, 20], page out the region", check the entered scheme again, and
+finally remove the scheme. ::
+
+    # cd <debugfs>/damon
+    # echo "4096 8192    0 5    10 20    2" > schemes
+    # cat schemes
+    4096 8192 0 5 10 20 2 0 0
+    # echo > schemes
+
+The last two integers in the 4th line of above example is the total number and
+the total size of the regions that the scheme is applied.
+
 Turning On/Off
 --------------
 
diff --git a/Documentation/vm/damon/index.rst b/Documentation/vm/damon/index.rst
index 17dca3c12aad..69aec1287aaf 100644
--- a/Documentation/vm/damon/index.rst
+++ b/Documentation/vm/damon/index.rst
@@ -28,4 +28,3 @@ workloads and systems.
    design
    eval
    api
-   plans
-- 
2.17.1