[RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[Stefan Roesch]

So far KSM can only be enabled by calling madvise for memory regions. What is
required to enable KSM for more workloads is to enable / disable it at the
process / cgroup level.

1. New options for prctl system command
This patch series adds two new options to the prctl system call. The first
one allows to enable KSM at the process level and the second one to query the
setting.

The setting will be inherited by child processes.

With the above setting, KSM can be enabled for the seed process of a cgroup
and all processes in the cgroup will inherit the setting.

2. Changes to KSM processing
When KSM is enabled at the process level, the KSM code will iterate over all
the VMA's and enable KSM for the eligible VMA's.

When forking a process that has KSM enabled, the setting will be inherited by
the new child process.

In addition when KSM is disabled for a process, KSM will be disabled for the
VMA's where KSM has been enabled.

3. Add tracepoints to KSM
Currently KSM has no tracepoints. This adds tracepoints to the key KSM functions
to make it easier to debug KSM.

4. Add general_profit metric
The general_profit metric of KSM is specified in the documentation, but not
calculated. This adds the general profit metric to /sys/kernel/debug/mm/ksm.

5. Add more metrics to ksm_stat
This adds the process profit and ksm type metric to /proc/<pid>/ksm_stat.

6. Add more tests to ksm_tests
This adds an option to specify the merge type to the ksm_tests. This allows to
test madvise and prctl KSM. It also adds a new option to query if prctl KSM has
been enabled. It adds a fork test to verify that the KSM process setting is
inherited by client processes.


Stefan Roesch (20):
  mm: add new flag to enable ksm per process
  mm: add flag to __ksm_enter
  mm: add flag to __ksm_exit call
  mm: invoke madvise for all vmas in scan_get_next_rmap_item
  mm: support disabling of ksm for a process
  mm: add new prctl option to get and set ksm for a process
  mm: add tracepoints to ksm
  mm: split off pages_volatile function
  mm: expose general_profit metric
  docs: document general_profit sysfs knob
  mm: calculate ksm process profit metric
  mm: add ksm_merge_type() function
  mm: expose ksm process profit metric in ksm_stat
  mm: expose ksm merge type in ksm_stat
  docs: document new procfs ksm knobs
  tools: add new prctl flags to prctl in tools dir
  selftests/vm: add KSM prctl merge test
  selftests/vm: add KSM get merge type test
  selftests/vm: add KSM fork test
  selftests/vm: add two functions for debugging merge outcome

 Documentation/ABI/testing/sysfs-kernel-mm-ksm |   8 +
 Documentation/admin-guide/mm/ksm.rst          |   8 +-
 MAINTAINERS                                   |   1 +
 fs/proc/base.c                                |   5 +
 include/linux/ksm.h                           |  19 +-
 include/linux/sched/coredump.h                |   1 +
 include/trace/events/ksm.h                    | 257 ++++++++++++++++++
 include/uapi/linux/prctl.h                    |   2 +
 kernel/sys.c                                  |  29 ++
 mm/ksm.c                                      | 134 ++++++++-
 tools/include/uapi/linux/prctl.h              |   2 +
 tools/testing/selftests/vm/Makefile           |   3 +-
 tools/testing/selftests/vm/ksm_tests.c        | 254 ++++++++++++++---
 13 files changed, 665 insertions(+), 58 deletions(-)
 create mode 100644 include/trace/events/ksm.h


base-commit: c1649ec55708ae42091a2f1bca1ab49ecd722d55
-- 
2.30.2

[RESEND RFC PATCH v1 01/20] mm: add new flag to enable ksm per process

[Stefan Roesch]

This introduces the new flag MMF_VM_MERGE_ANY flag. When this flag is
set, kernel samepage merging (ksm) gets enabled for all vma's of a
process.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/linux/sched/coredump.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/sched/coredump.h b/include/linux/sched/coredump.h
index 8270ad7ae14c..0e0de5b7469f 100644
--- a/include/linux/sched/coredump.h
+++ b/include/linux/sched/coredump.h
@@ -86,4 +86,5 @@ static inline int get_dumpable(struct mm_struct *mm)
 #define MMF_INIT_MASK		(MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
 				 MMF_DISABLE_THP_MASK)
 
+#define MMF_VM_MERGE_ANY	29
 #endif /* _LINUX_SCHED_COREDUMP_H */
-- 
2.30.2

[RESEND RFC PATCH v1 02/20] mm: add flag to __ksm_enter

[Stefan Roesch]

This change adds the flag parameter to __ksm_enter. This allows to
distinguish if ksm was called by prctl or madvise.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/linux/ksm.h | 6 ++++--
 mm/ksm.c            | 9 +++++----
 2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 7e232ba59b86..50e6b56092f3 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -18,13 +18,15 @@
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags);
-int __ksm_enter(struct mm_struct *mm);
 void __ksm_exit(struct mm_struct *mm);
+int __ksm_enter(struct mm_struct *mm, int flag);
 
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
+	if (test_bit(MMF_VM_MERGE_ANY, &oldmm->flags))
+		return __ksm_enter(mm, MMF_VM_MERGE_ANY);
 	if (test_bit(MMF_VM_MERGEABLE, &oldmm->flags))
-		return __ksm_enter(mm);
+		return __ksm_enter(mm, MMF_VM_MERGEABLE);
 	return 0;
 }
 
diff --git a/mm/ksm.c b/mm/ksm.c
index dd02780c387f..d84a244fe224 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2493,8 +2493,9 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 			return 0;
 #endif
 
-		if (!test_bit(MMF_VM_MERGEABLE, &mm->flags)) {
-			err = __ksm_enter(mm);
+		if (!test_bit(MMF_VM_MERGEABLE, &mm->flags) &&
+		    !test_bit(MMF_VM_MERGE_ANY, &mm->flags)) {
+			err = __ksm_enter(mm, MMF_VM_MERGEABLE);
 			if (err)
 				return err;
 		}
@@ -2520,7 +2521,7 @@ int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 }
 EXPORT_SYMBOL_GPL(ksm_madvise);
 
-int __ksm_enter(struct mm_struct *mm)
+int __ksm_enter(struct mm_struct *mm, int flag)
 {
 	struct ksm_mm_slot *mm_slot;
 	struct mm_slot *slot;
@@ -2553,7 +2554,7 @@ int __ksm_enter(struct mm_struct *mm)
 		list_add_tail(&slot->mm_node, &ksm_scan.mm_slot->slot.mm_node);
 	spin_unlock(&ksm_mmlist_lock);
 
-	set_bit(MMF_VM_MERGEABLE, &mm->flags);
+	set_bit(flag, &mm->flags);
 	mmgrab(mm);
 
 	if (needs_wakeup)
-- 
2.30.2

[RESEND RFC PATCH v1 03/20] mm: add flag to __ksm_exit call

[Stefan Roesch]

This adds the flag parameter to the __ksm_exit() call. This allows to
distinguish if this call is for an prctl or madvise invocation.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/linux/ksm.h | 8 +++++---
 mm/ksm.c            | 8 ++++++--
 2 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index 50e6b56092f3..d38a05a36298 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -18,8 +18,8 @@
 #ifdef CONFIG_KSM
 int ksm_madvise(struct vm_area_struct *vma, unsigned long start,
 		unsigned long end, int advice, unsigned long *vm_flags);
-void __ksm_exit(struct mm_struct *mm);
 int __ksm_enter(struct mm_struct *mm, int flag);
+void __ksm_exit(struct mm_struct *mm, int flag);
 
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
@@ -32,8 +32,10 @@ static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 
 static inline void ksm_exit(struct mm_struct *mm)
 {
-	if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
-		__ksm_exit(mm);
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGE_ANY);
+	else if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		__ksm_exit(mm, MMF_VM_MERGEABLE);
 }
 
 /*
diff --git a/mm/ksm.c b/mm/ksm.c
index d84a244fe224..83796328574c 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2563,12 +2563,16 @@ int __ksm_enter(struct mm_struct *mm, int flag)
 	return 0;
 }
 
-void __ksm_exit(struct mm_struct *mm)
+void __ksm_exit(struct mm_struct *mm, int flag)
 {
 	struct ksm_mm_slot *mm_slot;
 	struct mm_slot *slot;
 	int easy_to_free = 0;
 
+	if (!(current->flags & PF_EXITING) && flag == MMF_VM_MERGE_ANY &&
+	    test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
+
 	/*
 	 * This process is exiting: if it's straightforward (as is the
 	 * case when ksmd was never running), free mm_slot immediately.
@@ -2595,7 +2599,7 @@ void __ksm_exit(struct mm_struct *mm)
 
 	if (easy_to_free) {
 		mm_slot_free(mm_slot_cache, mm_slot);
-		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+		clear_bit(flag, &mm->flags);
 		mmdrop(mm);
 	} else if (mm_slot) {
 		mmap_write_lock(mm);
-- 
2.30.2

[RESEND RFC PATCH v1 04/20] mm: invoke madvise for all vmas in scan_get_next_rmap_item

[Stefan Roesch]

If the new flag MMF_VM_MERGE_ANY has been set for a process, iterate
over all the vmas and enable ksm if possible. For the vmas that can be
ksm enabled this is only done once.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 mm/ksm.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 83796328574c..967eda719fab 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1013,6 +1013,7 @@ static int unmerge_and_remove_all_rmap_items(void)
 
 			mm_slot_free(mm_slot_cache, mm_slot);
 			clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+			clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
 			mmdrop(mm);
 		} else
 			spin_unlock(&ksm_mmlist_lock);
@@ -2243,6 +2244,17 @@ static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot,
 	return rmap_item;
 }
 
+static bool vma_ksm_mergeable(struct vm_area_struct *vma)
+{
+	if (vma->vm_flags & VM_MERGEABLE)
+		return true;
+
+	if (test_bit(MMF_VM_MERGE_ANY, &vma->vm_mm->flags))
+		return true;
+
+	return false;
+}
+
 static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 {
 	struct mm_struct *mm;
@@ -2319,8 +2331,20 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 		goto no_vmas;
 
 	for_each_vma(vmi, vma) {
-		if (!(vma->vm_flags & VM_MERGEABLE))
+		if (!vma_ksm_mergeable(vma))
 			continue;
+		if (!(vma->vm_flags & VM_MERGEABLE)) {
+			unsigned long flags = vma->vm_flags;
+
+			/* madvise failed, use next vma */
+			if (ksm_madvise(vma, vma->vm_start, vma->vm_end, MADV_MERGEABLE, &flags))
+				continue;
+			/* vma, not supported as being mergeable */
+			if (!(flags & VM_MERGEABLE))
+				continue;
+
+			vma->vm_flags = flags;
+		}
 		if (ksm_scan.address < vma->vm_start)
 			ksm_scan.address = vma->vm_start;
 		if (!vma->anon_vma)
@@ -2389,6 +2413,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 
 		mm_slot_free(mm_slot_cache, mm_slot);
 		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
+		clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
 		mmap_read_unlock(mm);
 		mmdrop(mm);
 	} else {
-- 
2.30.2

[RESEND RFC PATCH v1 05/20] mm: support disabling of ksm for a process

[Stefan Roesch]

This adds the ability to disable ksm for a process if ksm has been
enabled for the process.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 mm/ksm.c | 25 ++++++++++++++++++++++++-
 1 file changed, 24 insertions(+), 1 deletion(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 967eda719fab..5fa6b46dfa3b 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2588,6 +2588,27 @@ int __ksm_enter(struct mm_struct *mm, int flag)
 	return 0;
 }
 
+static void unmerge_vmas(struct mm_struct *mm)
+{
+	struct vm_area_struct *vma;
+	struct vma_iterator vmi;
+
+	vma_iter_init(&vmi, mm, 0);
+
+	mmap_read_lock(mm);
+	for_each_vma(vmi, vma) {
+		if (vma->vm_flags & VM_MERGEABLE) {
+			unsigned long flags = vma->vm_flags;
+
+			if (ksm_madvise(vma, vma->vm_start, vma->vm_end, MADV_UNMERGEABLE, &flags))
+				continue;
+
+			vma->vm_flags = flags;
+		}
+	}
+	mmap_read_unlock(mm);
+}
+
 void __ksm_exit(struct mm_struct *mm, int flag)
 {
 	struct ksm_mm_slot *mm_slot;
@@ -2595,8 +2616,10 @@ void __ksm_exit(struct mm_struct *mm, int flag)
 	int easy_to_free = 0;
 
 	if (!(current->flags & PF_EXITING) && flag == MMF_VM_MERGE_ANY &&
-	    test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		test_bit(MMF_VM_MERGE_ANY, &mm->flags)) {
 		clear_bit(MMF_VM_MERGE_ANY, &mm->flags);
+		unmerge_vmas(mm);
+	}
 
 	/*
 	 * This process is exiting: if it's straightforward (as is the
-- 
2.30.2

[RESEND RFC PATCH v1 06/20] mm: add new prctl option to get and set ksm for a process

[Stefan Roesch]

This adds two new options to the prctl system call
- enable ksm for all vmas of a process (if the vmas support it).
- query if ksm has been enabled for a process.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/uapi/linux/prctl.h |  2 ++
 kernel/sys.c               | 29 +++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index a5e06dcbba13..b8ba85f18e43 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -284,4 +284,6 @@ struct prctl_mm_map {
 #define PR_SET_VMA		0x53564d41
 # define PR_SET_VMA_ANON_NAME		0
 
+#define PR_SET_MEMORY_MERGE		65
+#define PR_GET_MEMORY_MERGE		66
 #endif /* _LINUX_PRCTL_H */
diff --git a/kernel/sys.c b/kernel/sys.c
index 5fd54bf0e886..de218e3b6f42 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -15,6 +15,7 @@
 #include <linux/highuid.h>
 #include <linux/fs.h>
 #include <linux/kmod.h>
+#include <linux/ksm.h>
 #include <linux/perf_event.h>
 #include <linux/resource.h>
 #include <linux/kernel.h>
@@ -2626,6 +2627,34 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	case PR_SET_VMA:
 		error = prctl_set_vma(arg2, arg3, arg4, arg5);
 		break;
+#ifdef CONFIG_KSM
+	case PR_SET_MEMORY_MERGE:
+		if (!capable(CAP_SYS_RESOURCE))
+			return -EPERM;
+
+		if (arg2) {
+			if (mmap_write_lock_killable(me->mm))
+				return -EINTR;
+
+			if (test_bit(MMF_VM_MERGEABLE, &me->mm->flags))
+				error = -EINVAL;
+			else if (!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags))
+				error = __ksm_enter(me->mm, MMF_VM_MERGE_ANY);
+			mmap_write_unlock(me->mm);
+		} else {
+			__ksm_exit(me->mm, MMF_VM_MERGE_ANY);
+		}
+		break;
+	case PR_GET_MEMORY_MERGE:
+		if (!capable(CAP_SYS_RESOURCE))
+			return -EPERM;
+
+		if (arg2 || arg3 || arg4 || arg5)
+			return -EINVAL;
+
+		error = !!test_bit(MMF_VM_MERGE_ANY, &me->mm->flags);
+		break;
+#endif
 	default:
 		error = -EINVAL;
 		break;
-- 
2.30.2

[RESEND RFC PATCH v1 07/20] mm: add tracepoints to ksm

[Stefan Roesch]

This adds the following tracepoints to ksm:
- start / stop scan
- ksm enter / exit
- merge a page
- merge a page with ksm
- remove a page
- remove a rmap item

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 MAINTAINERS                |   1 +
 include/trace/events/ksm.h | 257 +++++++++++++++++++++++++++++++++++++
 mm/ksm.c                   |  20 ++-
 3 files changed, 276 insertions(+), 2 deletions(-)
 create mode 100644 include/trace/events/ksm.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 123216b76534..990a28bdc263 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -13482,6 +13482,7 @@ F:	include/linux/memory_hotplug.h
 F:	include/linux/mm.h
 F:	include/linux/mmzone.h
 F:	include/linux/pagewalk.h
+F:	include/trace/events/ksm.h
 F:	mm/
 F:	tools/testing/selftests/vm/
 
diff --git a/include/trace/events/ksm.h b/include/trace/events/ksm.h
new file mode 100644
index 000000000000..727d8f6dbc3f
--- /dev/null
+++ b/include/trace/events/ksm.h
@@ -0,0 +1,257 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#undef TRACE_SYSTEM
+#define TRACE_SYSTEM ksm
+
+#if !defined(_TRACE_KSM_H) || defined(TRACE_HEADER_MULTI_READ)
+#define _TRACE_KSM_H
+
+#include <linux/tracepoint.h>
+
+/**
+ * ksm_scan_template - called for start / stop scan
+ *
+ * @seq:		sequence number of scan
+ * @rmap_entries:	actual number of rmap entries
+ *
+ * Allows to trace the start / stop of a ksm scan.
+ */
+DECLARE_EVENT_CLASS(ksm_scan_template,
+
+	TP_PROTO(int seq, u32 rmap_entries),
+
+	TP_ARGS(seq, rmap_entries),
+
+	TP_STRUCT__entry(
+		__field(int,	seq)
+		__field(u32,	rmap_entries)
+	),
+
+	TP_fast_assign(
+		__entry->seq		= seq;
+		__entry->rmap_entries	= rmap_entries;
+	),
+
+	TP_printk("seq %d rmap size %d",
+			__entry->seq, __entry->rmap_entries)
+);
+
+/**
+ * ksm_start_scan - called after a new ksm scan is started
+ *
+ * @seq:		sequence number of scan
+ * @rmap_entries:	actual number of rmap entries
+ *
+ * Allows to trace the start of a ksm scan.
+ */
+DEFINE_EVENT(ksm_scan_template, ksm_start_scan,
+
+	TP_PROTO(int seq, u32 rmap_entries),
+
+	TP_ARGS(seq, rmap_entries)
+);
+
+/**
+ * ksm_stop_scan - called after a new ksm scan has completed
+ *
+ * @seq:		sequence number of scan
+ * @rmap_entries:	actual number of rmap entries
+ *
+ * Allows to trace the completion of a ksm scan.
+ */
+DEFINE_EVENT(ksm_scan_template, ksm_stop_scan,
+
+	TP_PROTO(int seq, u32 rmap_entries),
+
+	TP_ARGS(seq, rmap_entries)
+);
+
+/**
+ * ksm_enter - called after a new process has been added / removed from ksm
+ *
+ * @mm:			address of the mm object of the process
+ * @flag:		specified flags
+ *
+ * Allows to trace the when a process has been added or removed from ksm.
+ */
+DECLARE_EVENT_CLASS(ksm_enter_exit_template,
+
+	TP_PROTO(void *mm, unsigned int flag),
+
+	TP_ARGS(mm, flag),
+
+	TP_STRUCT__entry(
+		__field(void *,		mm)
+		__field(unsigned int,	flag)
+	),
+
+	TP_fast_assign(
+		__entry->mm	= mm;
+		__entry->flag	= flag;
+	),
+
+	TP_printk("mm %p flag %u",
+		__entry->mm, __entry->flag)
+);
+
+/**
+ * ksm_enter - called after a new process has been added to ksm
+ *
+ * @mm:			address of the mm object of the process
+ * @flag:		specified flags
+ *
+ * Allows to trace the when a process has been added to ksm.
+ */
+DEFINE_EVENT(ksm_enter_exit_template, ksm_enter,
+
+	TP_PROTO(void *mm, unsigned int flag),
+
+	TP_ARGS(mm, flag)
+);
+
+/**
+ * ksm_exit - called after a new process has been removed from ksm
+ *
+ * @mm:			address of the mm object of the process
+ * @flag:		specified flags
+ *
+ * Allows to trace the when a process has been removed from ksm.
+ */
+DEFINE_EVENT(ksm_enter_exit_template, ksm_exit,
+
+	TP_PROTO(void *mm, unsigned int flag),
+
+	TP_ARGS(mm, flag)
+);
+
+/**
+ * ksm_merge_one_page - called after a page has been merged
+ *
+ * @pfn:		page frame number of ksm page
+ * @rmap_item:		address of rmap_item  object
+ * @mm:			address of the process mm struct
+ * @err:		success
+ *
+ * Allows to trace the ksm merging of individual pages.
+ */
+TRACE_EVENT(ksm_merge_one_page,
+
+	TP_PROTO(unsigned long pfn, void *rmap_item, void *mm, int err),
+
+	TP_ARGS(pfn, rmap_item, mm, err),
+
+	TP_STRUCT__entry(
+		__field(unsigned long,	pfn)
+		__field(void *,		rmap_item)
+		__field(void *,		mm)
+		__field(int,		err)
+	),
+
+	TP_fast_assign(
+		__entry->pfn		= pfn;
+		__entry->rmap_item	= rmap_item;
+		__entry->mm		= mm;
+		__entry->err		= err;
+	),
+
+	TP_printk("ksm pfn %lu rmap_item %p mm %p error %d",
+			__entry->pfn, __entry->rmap_item, __entry->mm, __entry->err)
+);
+
+/**
+ * ksm_merge_with_ksm_page - called after a page has been merged with a ksm page
+ *
+ * @ksm_page:		address ksm page
+ * @pfn:		page frame number of ksm page
+ * @rmap_item:		address of rmap_item  object
+ * @mm:			address of the mm object of the process
+ * @err:		success
+ *
+ * Allows to trace the merging of a page with a ksm page.
+ */
+TRACE_EVENT(ksm_merge_with_ksm_page,
+
+	TP_PROTO(void *ksm_page, unsigned long pfn, void *rmap_item, void *mm, int err),
+
+	TP_ARGS(ksm_page, pfn, rmap_item, mm, err),
+
+	TP_STRUCT__entry(
+		__field(void *,		ksm_page)
+		__field(unsigned long,	pfn)
+		__field(void *,		rmap_item)
+		__field(void *,		mm)
+		__field(int,		err)
+	),
+
+	TP_fast_assign(
+		__entry->ksm_page	= ksm_page;
+		__entry->pfn		= pfn;
+		__entry->rmap_item	= rmap_item;
+		__entry->mm		= mm;
+		__entry->err		= err;
+	),
+
+	TP_printk("%spfn %lu rmap_item %p mm %p error %d",
+		  (__entry->ksm_page ? "ksm " : ""),
+		  __entry->pfn, __entry->rmap_item, __entry->mm, __entry->err)
+);
+
+/**
+ * ksm_remove_ksm_page - called after a ksm page has been removed
+ *
+ * @pfn:		page frame number of ksm page
+ *
+ * Allows to trace the removing of stable ksm pages.
+ */
+TRACE_EVENT(ksm_remove_ksm_page,
+
+	TP_PROTO(unsigned long pfn),
+
+	TP_ARGS(pfn),
+
+	TP_STRUCT__entry(
+		__field(unsigned long, pfn)
+	),
+
+	TP_fast_assign(
+		__entry->pfn = pfn;
+	),
+
+	TP_printk("pfn %lu", __entry->pfn)
+);
+
+/**
+ * ksm_remove_rmap_item - called after a rmap_item has been removed from the
+ *                        stable tree
+ *
+ * @pfn:		page frame number of ksm page
+ * @rmap_item:		address of rmap_item  object
+ * @mm:			address of the process mm struct
+ *
+ * Allows to trace the removal of pages from the stable tree list.
+ */
+TRACE_EVENT(ksm_remove_rmap_item,
+
+	TP_PROTO(unsigned long pfn, void *rmap_item, void *mm),
+
+	TP_ARGS(pfn, rmap_item, mm),
+
+	TP_STRUCT__entry(
+		__field(unsigned long,	pfn)
+		__field(void *,		rmap_item)
+		__field(void *,		mm)
+	),
+
+	TP_fast_assign(
+		__entry->pfn		= pfn;
+		__entry->rmap_item	= rmap_item;
+		__entry->mm		= mm;
+	),
+
+	TP_printk("pfn %lu rmap_item %p mm %p",
+			__entry->pfn, __entry->rmap_item, __entry->mm)
+);
+
+#endif /* _TRACE_KSM_H */
+
+/* This part must be outside protection */
+#include <trace/define_trace.h>
diff --git a/mm/ksm.c b/mm/ksm.c
index 5fa6b46dfa3b..88a969849955 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -45,6 +45,9 @@
 #include "internal.h"
 #include "mm_slot.h"
 
+#define CREATE_TRACE_POINTS
+#include <trace/events/ksm.h>
+
 #ifdef CONFIG_NUMA
 #define NUMA(x)		(x)
 #define DO_NUMA(x)	do { (x); } while (0)
@@ -633,10 +636,12 @@ static void remove_node_from_stable_tree(struct ksm_stable_node *stable_node)
 	BUG_ON(stable_node->rmap_hlist_len < 0);
 
 	hlist_for_each_entry(rmap_item, &stable_node->hlist, hlist) {
-		if (rmap_item->hlist.next)
+		if (rmap_item->hlist.next) {
+			trace_ksm_remove_rmap_item(stable_node->kpfn, rmap_item, rmap_item->mm);
 			ksm_pages_sharing--;
-		else
+		} else {
 			ksm_pages_shared--;
+		}
 
 		rmap_item->mm->ksm_merging_pages--;
 
@@ -657,6 +662,7 @@ static void remove_node_from_stable_tree(struct ksm_stable_node *stable_node)
 	BUILD_BUG_ON(STABLE_NODE_DUP_HEAD <= &migrate_nodes);
 	BUILD_BUG_ON(STABLE_NODE_DUP_HEAD >= &migrate_nodes + 1);
 
+	trace_ksm_remove_ksm_page(stable_node->kpfn);
 	if (stable_node->head == &migrate_nodes)
 		list_del(&stable_node->list);
 	else
@@ -1319,6 +1325,8 @@ static int try_to_merge_with_ksm_page(struct ksm_rmap_item *rmap_item,
 	get_anon_vma(vma->anon_vma);
 out:
 	mmap_read_unlock(mm);
+	trace_ksm_merge_with_ksm_page(kpage, page_to_pfn(kpage ? kpage : page),
+				rmap_item, mm, err);
 	return err;
 }
 
@@ -2137,6 +2145,8 @@ static void cmp_and_merge_page(struct page *page, struct ksm_rmap_item *rmap_ite
 		if (vma) {
 			err = try_to_merge_one_page(vma, page,
 					ZERO_PAGE(rmap_item->address));
+			trace_ksm_merge_one_page(page_to_pfn(ZERO_PAGE(rmap_item->address)),
+							rmap_item, mm, err);
 		} else {
 			/*
 			 * If the vma is out of date, we do not need to
@@ -2270,6 +2280,8 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 
 	mm_slot = ksm_scan.mm_slot;
 	if (mm_slot == &ksm_mm_head) {
+		trace_ksm_start_scan(ksm_scan.seqnr, ksm_rmap_items);
+
 		/*
 		 * A number of pages can hang around indefinitely on per-cpu
 		 * pagevecs, raised page count preventing write_protect_page
@@ -2433,6 +2445,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 	if (mm_slot != &ksm_mm_head)
 		goto next_mm;
 
+	trace_ksm_stop_scan(ksm_scan.seqnr, ksm_rmap_items);
 	ksm_scan.seqnr++;
 	return NULL;
 }
@@ -2585,6 +2598,7 @@ int __ksm_enter(struct mm_struct *mm, int flag)
 	if (needs_wakeup)
 		wake_up_interruptible(&ksm_thread_wait);
 
+	trace_ksm_enter(mm, flag);
 	return 0;
 }
 
@@ -2653,6 +2667,8 @@ void __ksm_exit(struct mm_struct *mm, int flag)
 		mmap_write_lock(mm);
 		mmap_write_unlock(mm);
 	}
+
+	trace_ksm_exit(mm, flag);
 }
 
 struct page *ksm_might_need_to_copy(struct page *page,
-- 
2.30.2

Re: [RESEND RFC PATCH v1 07/20] mm: add tracepoints to ksm

[Steven Rostedt]

On Mon, 23 Jan 2023 09:37:35 -0800
Stefan Roesch <shr@devkernel.io> wrote:

> This adds the following tracepoints to ksm:
> - start / stop scan
> - ksm enter / exit
> - merge a page
> - merge a page with ksm
> - remove a page
> - remove a rmap item
> 
> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> ---
>  MAINTAINERS                |   1 +
>  include/trace/events/ksm.h | 257 +++++++++++++++++++++++++++++++++++++
>  mm/ksm.c                   |  20 ++-
>  3 files changed, 276 insertions(+), 2 deletions(-)
>  create mode 100644 include/trace/events/ksm.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 123216b76534..990a28bdc263 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -13482,6 +13482,7 @@ F:	include/linux/memory_hotplug.h
>  F:	include/linux/mm.h
>  F:	include/linux/mmzone.h
>  F:	include/linux/pagewalk.h
> +F:	include/trace/events/ksm.h
>  F:	mm/
>  F:	tools/testing/selftests/vm/
>  

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve

[RESEND RFC PATCH v1 08/20] mm: split off pages_volatile function

[Stefan Roesch]

This splits off the pages_volatile function. The next patch will use
this function.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 mm/ksm.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 88a969849955..19f434f97dc1 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3182,8 +3182,7 @@ static ssize_t pages_unshared_show(struct kobject *kobj,
 }
 KSM_ATTR_RO(pages_unshared);
 
-static ssize_t pages_volatile_show(struct kobject *kobj,
-				   struct kobj_attribute *attr, char *buf)
+static long pages_volatile(void)
 {
 	long ksm_pages_volatile;
 
@@ -3195,7 +3194,14 @@ static ssize_t pages_volatile_show(struct kobject *kobj,
 	 */
 	if (ksm_pages_volatile < 0)
 		ksm_pages_volatile = 0;
-	return sysfs_emit(buf, "%ld\n", ksm_pages_volatile);
+
+	return ksm_pages_volatile;
+}
+
+static ssize_t pages_volatile_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	return sysfs_emit(buf, "%ld\n", pages_volatile());
 }
 KSM_ATTR_RO(pages_volatile);
 
-- 
2.30.2

[RESEND RFC PATCH v1 09/20] mm: expose general_profit metric

[Stefan Roesch]

The documentation mentions a general profit metric, however this metric
is not calculated. In addition the formula depends on the size of
internal structures, which makes it more difficult for an administrator
to make the calculation. Adding the metric for a better user experience.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 mm/ksm.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/mm/ksm.c b/mm/ksm.c
index 19f434f97dc1..d29454a802a0 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3205,6 +3205,21 @@ static ssize_t pages_volatile_show(struct kobject *kobj,
 }
 KSM_ATTR_RO(pages_volatile);
 
+static ssize_t general_profit_show(struct kobject *kobj,
+				   struct kobj_attribute *attr, char *buf)
+{
+	long general_profit;
+	long all_rmap_items;
+
+	all_rmap_items = ksm_max_page_sharing + ksm_pages_shared +
+				ksm_pages_unshared + pages_volatile();
+	general_profit = ksm_pages_sharing * PAGE_SIZE -
+				all_rmap_items * sizeof(struct ksm_rmap_item);
+
+	return sysfs_emit(buf, "%ld\n", general_profit);
+}
+KSM_ATTR_RO(general_profit);
+
 static ssize_t stable_node_dups_show(struct kobject *kobj,
 				     struct kobj_attribute *attr, char *buf)
 {
@@ -3269,6 +3284,7 @@ static struct attribute *ksm_attrs[] = {
 	&stable_node_dups_attr.attr,
 	&stable_node_chains_prune_millisecs_attr.attr,
 	&use_zero_pages_attr.attr,
+	&general_profit_attr.attr,
 	NULL,
 };
 
-- 
2.30.2

[RESEND RFC PATCH v1 10/20] docs: document general_profit sysfs knob

[Stefan Roesch]

This adds documentation for the new /sys/kernel/mm/ksm/general_profit
knob.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 Documentation/ABI/testing/sysfs-kernel-mm-ksm | 8 ++++++++
 Documentation/admin-guide/mm/ksm.rst          | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
index d244674a9480..7768e90f7a8f 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
@@ -51,3 +51,11 @@ Description:	Control merging pages across different NUMA nodes.
 
 		When it is set to 0 only pages from the same node are merged,
 		otherwise pages from all nodes can be merged together (default).
+
+What:		/sys/kernel/mm/ksm/general_profit
+Date:		January 2023
+KernelVersion:  6.1
+Contact:	Linux memory management mailing list <linux-mm@kvack.org>
+Description:	Measure how effective KSM is.
+		general_profit: how effective is KSM. The formula for the
+		calculation is in Documentation/admin-guide/mm/ksm.rst.
diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index fb6ba2002a4b..72189bf1283e 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -159,6 +159,8 @@ stable_node_chains_prune_millisecs
 
 The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
+general_profit
+        how effective is KSM. The calculation is explained below.
 pages_shared
         how many shared pages are being used
 pages_sharing
-- 
2.30.2

Re: [RESEND RFC PATCH v1 10/20] docs: document general_profit sysfs knob

[Bagas Sanjaya]

[-- Attachment #1: Type: text/plain, Size: 3608 bytes --]

On Mon, Jan 23, 2023 at 09:37:38AM -0800, Stefan Roesch wrote:
> This adds documentation for the new /sys/kernel/mm/ksm/general_profit
> knob.

"Document general_profit knob."

> 
> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> ---
>  Documentation/ABI/testing/sysfs-kernel-mm-ksm | 8 ++++++++
>  Documentation/admin-guide/mm/ksm.rst          | 2 ++
>  2 files changed, 10 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> index d244674a9480..7768e90f7a8f 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> @@ -51,3 +51,11 @@ Description:	Control merging pages across different NUMA nodes.
>  
>  		When it is set to 0 only pages from the same node are merged,
>  		otherwise pages from all nodes can be merged together (default).
> +
> +What:		/sys/kernel/mm/ksm/general_profit
> +Date:		January 2023
> +KernelVersion:  6.1
> +Contact:	Linux memory management mailing list <linux-mm@kvack.org>
> +Description:	Measure how effective KSM is.
> +		general_profit: how effective is KSM. The formula for the
> +		calculation is in Documentation/admin-guide/mm/ksm.rst.
> diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
> index fb6ba2002a4b..72189bf1283e 100644
> --- a/Documentation/admin-guide/mm/ksm.rst
> +++ b/Documentation/admin-guide/mm/ksm.rst
> @@ -159,6 +159,8 @@ stable_node_chains_prune_millisecs
>  
>  The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
>  
> +general_profit
> +        how effective is KSM. The calculation is explained below.
>  pages_shared
>          how many shared pages are being used
>  pages_sharing

Seems like the wording is confusing me, so I write the improv:

---- >8 ----
diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
index 7768e90f7a8fef..5309a912ab679b 100644
--- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm
+++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
@@ -56,6 +56,6 @@ What:		/sys/kernel/mm/ksm/general_profit
 Date:		January 2023
 KernelVersion:  6.1
 Contact:	Linux memory management mailing list <linux-mm@kvack.org>
-Description:	Measure how effective KSM is.
-		general_profit: how effective is KSM. The formula for the
-		calculation is in Documentation/admin-guide/mm/ksm.rst.
+Description:	Measure the KSM profit. See
+		:ref:`KSM documentation <monitoring-ksm-profit>` for details
+		on the calculated formula.
diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index 70896f01d64106..fb67318aab1ba2 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -160,7 +160,8 @@ stable_node_chains_prune_millisecs
 The effectiveness of KSM and MADV_MERGEABLE is shown in ``/sys/kernel/mm/ksm/``:
 
 general_profit
-        how effective is KSM. The calculation is explained below.
+        the KSM profit. The calculation is described :ref:`below
+        <monitoring-ksm-profit>`.
 pages_shared
         how many shared pages are being used
 pages_sharing
@@ -186,6 +187,8 @@ The maximum possible ``pages_sharing/pages_shared`` ratio is limited by the
 ``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` must
 be increased accordingly.
 
+.. _monitoring-ksm-profit:
+
 Monitoring KSM profit
 =====================
 
Thanks.

-- 
An old man doll... just what I always wanted! - Clara

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Re: [RESEND RFC PATCH v1 10/20] docs: document general_profit sysfs knob

[Jonathan Corbet]

Bagas Sanjaya <bagasdotme@gmail.com> writes:

> Seems like the wording is confusing me, so I write the improv:
>
> ---- >8 ----
> diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> index 7768e90f7a8fef..5309a912ab679b 100644
> --- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> +++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> @@ -56,6 +56,6 @@ What:		/sys/kernel/mm/ksm/general_profit
>  Date:		January 2023
>  KernelVersion:  6.1
>  Contact:	Linux memory management mailing list <linux-mm@kvack.org>
> -Description:	Measure how effective KSM is.
> -		general_profit: how effective is KSM. The formula for the
> -		calculation is in Documentation/admin-guide/mm/ksm.rst.
> +Description:	Measure the KSM profit. See
> +		:ref:`KSM documentation <monitoring-ksm-profit>` for details
> +		on the calculated formula.

So the original at least attempted to tell us what "KSM profit" is; the
"improved" version makes no such effort.  I don't think that is actually
better.

jon

Re: [RESEND RFC PATCH v1 10/20] docs: document general_profit sysfs knob

[Bagas Sanjaya]

[-- Attachment #1: Type: text/plain, Size: 1261 bytes --]

On Tue, Jan 24, 2023 at 09:21:51AM -0700, Jonathan Corbet wrote:
> Bagas Sanjaya <bagasdotme@gmail.com> writes:
> 
> > Seems like the wording is confusing me, so I write the improv:
> >
> > ---- >8 ----
> > diff --git a/Documentation/ABI/testing/sysfs-kernel-mm-ksm b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> > index 7768e90f7a8fef..5309a912ab679b 100644
> > --- a/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> > +++ b/Documentation/ABI/testing/sysfs-kernel-mm-ksm
> > @@ -56,6 +56,6 @@ What:		/sys/kernel/mm/ksm/general_profit
> >  Date:		January 2023
> >  KernelVersion:  6.1
> >  Contact:	Linux memory management mailing list <linux-mm@kvack.org>
> > -Description:	Measure how effective KSM is.
> > -		general_profit: how effective is KSM. The formula for the
> > -		calculation is in Documentation/admin-guide/mm/ksm.rst.
> > +Description:	Measure the KSM profit. See
> > +		:ref:`KSM documentation <monitoring-ksm-profit>` for details
> > +		on the calculated formula.
> 
> So the original at least attempted to tell us what "KSM profit" is; the
> "improved" version makes no such effort.  I don't think that is actually
> better.

I overlooked that, thanks!

-- 
An old man doll... just what I always wanted! - Clara

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[RESEND RFC PATCH v1 11/20] mm: calculate ksm process profit metric

[Stefan Roesch]

The ksm documentation mentions the process profit metric and how to
calculate it. This adds the calculation of the metric.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/linux/ksm.h | 4 ++++
 mm/ksm.c            | 8 ++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index d38a05a36298..a18cd03efcfb 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -55,6 +55,10 @@ struct page *ksm_might_need_to_copy(struct page *page,
 void rmap_walk_ksm(struct folio *folio, struct rmap_walk_control *rwc);
 void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
 
+#ifdef CONFIG_PROC_FS
+long ksm_process_profit(struct mm_struct *);
+#endif /* CONFIG_PROC_FS */
+
 #else  /* !CONFIG_KSM */
 
 static inline int ksm_fork(struct mm_struct *mm, struct mm_struct *oldmm)
diff --git a/mm/ksm.c b/mm/ksm.c
index d29454a802a0..288689b59527 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2935,6 +2935,14 @@ static void wait_while_offlining(void)
 }
 #endif /* CONFIG_MEMORY_HOTREMOVE */
 
+#ifdef CONFIG_PROC_FS
+long ksm_process_profit(struct mm_struct *mm)
+{
+	return (long)mm->ksm_merging_pages * PAGE_SIZE -
+		mm->ksm_rmap_items * sizeof(struct ksm_rmap_item);
+}
+#endif /* CONFIG_PROC_FS */
+
 #ifdef CONFIG_SYSFS
 /*
  * This all compiles without CONFIG_SYSFS, but is a waste of space.
-- 
2.30.2

[RESEND RFC PATCH v1 12/20] mm: add ksm_merge_type() function

[Stefan Roesch]

This adds the ksm_merge_type function. The function returns the merge
type for the process. For madvise it returns "madvise", for prctl it
returns "process" and otherwise it returns "none".

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 include/linux/ksm.h |  1 +
 mm/ksm.c            | 11 +++++++++++
 2 files changed, 12 insertions(+)

diff --git a/include/linux/ksm.h b/include/linux/ksm.h
index a18cd03efcfb..d5f69f18ee5a 100644
--- a/include/linux/ksm.h
+++ b/include/linux/ksm.h
@@ -57,6 +57,7 @@ void folio_migrate_ksm(struct folio *newfolio, struct folio *folio);
 
 #ifdef CONFIG_PROC_FS
 long ksm_process_profit(struct mm_struct *);
+const char *ksm_merge_type(struct mm_struct *mm);
 #endif /* CONFIG_PROC_FS */
 
 #else  /* !CONFIG_KSM */
diff --git a/mm/ksm.c b/mm/ksm.c
index 288689b59527..57183deaf529 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -2941,6 +2941,17 @@ long ksm_process_profit(struct mm_struct *mm)
 	return (long)mm->ksm_merging_pages * PAGE_SIZE -
 		mm->ksm_rmap_items * sizeof(struct ksm_rmap_item);
 }
+
+/* Return merge type name as string. */
+const char *ksm_merge_type(struct mm_struct *mm)
+{
+	if (test_bit(MMF_VM_MERGE_ANY, &mm->flags))
+		return "process";
+	else if (test_bit(MMF_VM_MERGEABLE, &mm->flags))
+		return "madvise";
+	else
+		return "none";
+}
 #endif /* CONFIG_PROC_FS */
 
 #ifdef CONFIG_SYSFS
-- 
2.30.2

[RESEND RFC PATCH v1 13/20] mm: expose ksm process profit metric in ksm_stat

[Stefan Roesch]

This exposes the ksm process profit metric in /proc/<pid>/ksm_stat.
The documentation mentions the formula for the ksm process profit
metric, however it does not calculate it. In addition the formula
depends on the size of internal structures. So it makes sense to expose
it.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 fs/proc/base.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index 9e479d7d202b..a2b7779f76f6 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -96,6 +96,7 @@
 #include <linux/time_namespace.h>
 #include <linux/resctrl.h>
 #include <linux/cn_proc.h>
+#include <linux/ksm.h>
 #include <trace/events/oom.h>
 #include "internal.h"
 #include "fd.h"
@@ -3207,6 +3208,8 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
 	mm = get_task_mm(task);
 	if (mm) {
 		seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items);
+		seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
+		seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
 		mmput(mm);
 	}
 
-- 
2.30.2

[RESEND RFC PATCH v1 14/20] mm: expose ksm merge type in ksm_stat

[Stefan Roesch]

This exposes the ksm process type in /proc/<pid>/ksm_stat. The name of
the value is ksm_merge_type.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 fs/proc/base.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/proc/base.c b/fs/proc/base.c
index a2b7779f76f6..2b63a70fb7a6 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -3200,6 +3200,7 @@ static int proc_pid_ksm_merging_pages(struct seq_file *m, struct pid_namespace *
 
 	return 0;
 }
+
 static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
 				struct pid *pid, struct task_struct *task)
 {
@@ -3209,6 +3210,7 @@ static int proc_pid_ksm_stat(struct seq_file *m, struct pid_namespace *ns,
 	if (mm) {
 		seq_printf(m, "ksm_rmap_items %lu\n", mm->ksm_rmap_items);
 		seq_printf(m, "ksm_merging_pages %lu\n", mm->ksm_merging_pages);
+		seq_printf(m, "ksm_merge_type %s\n", ksm_merge_type(mm));
 		seq_printf(m, "ksm_process_profit %ld\n", ksm_process_profit(mm));
 		mmput(mm);
 	}
-- 
2.30.2

[RESEND RFC PATCH v1 15/20] docs: document new procfs ksm knobs

[Stefan Roesch]

This documents the ksm_process_profit and ksm_merge_type settings in
ksm_stat.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 Documentation/admin-guide/mm/ksm.rst | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
index 72189bf1283e..70896f01d641 100644
--- a/Documentation/admin-guide/mm/ksm.rst
+++ b/Documentation/admin-guide/mm/ksm.rst
@@ -211,7 +211,8 @@ several times, which are unprofitable memory consumed.
 			  ksm_rmap_items * sizeof(rmap_item).
 
    where ksm_merging_pages is shown under the directory ``/proc/<pid>/``,
-   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``.
+   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``. The process profit
+   is also shown in ``/proc/<pid>/ksm_stat`` as ksm_process_profit.
 
 From the perspective of application, a high ratio of ``ksm_rmap_items`` to
 ``ksm_merging_pages`` means a bad madvise-applied policy, so developers or
@@ -222,6 +223,9 @@ so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU
 or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped,
 because the ksm profit is approximately zero or negative.
 
+The ksm_merge_type in ``/proc/<pid>/ksm_stat`` shows the merge type of the
+process. Valid values are ``none``, ``madvise`` and ``process``.
+
 Monitoring KSM events
 =====================
 
-- 
2.30.2

Re: [RESEND RFC PATCH v1 15/20] docs: document new procfs ksm knobs

[Bagas Sanjaya]

[-- Attachment #1: Type: text/plain, Size: 1750 bytes --]

On Mon, Jan 23, 2023 at 09:37:43AM -0800, Stefan Roesch wrote:
> This documents the ksm_process_profit and ksm_merge_type settings in
> ksm_stat.

"Document both ksm_process_profit and ksm_merge_type proc settings."

> 
> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> ---
>  Documentation/admin-guide/mm/ksm.rst | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst
> index 72189bf1283e..70896f01d641 100644
> --- a/Documentation/admin-guide/mm/ksm.rst
> +++ b/Documentation/admin-guide/mm/ksm.rst
> @@ -211,7 +211,8 @@ several times, which are unprofitable memory consumed.
>  			  ksm_rmap_items * sizeof(rmap_item).
>  
>     where ksm_merging_pages is shown under the directory ``/proc/<pid>/``,
> -   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``.
> +   and ksm_rmap_items is shown in ``/proc/<pid>/ksm_stat``. The process profit
> +   is also shown in ``/proc/<pid>/ksm_stat`` as ksm_process_profit.
>  
>  From the perspective of application, a high ratio of ``ksm_rmap_items`` to
>  ``ksm_merging_pages`` means a bad madvise-applied policy, so developers or
> @@ -222,6 +223,9 @@ so if the ``ksm_rmap_items/ksm_merging_pages`` ratio exceeds 64 on 64-bit CPU
>  or exceeds 128 on 32-bit CPU, then the app's madvise policy should be dropped,
>  because the ksm profit is approximately zero or negative.
>  
> +The ksm_merge_type in ``/proc/<pid>/ksm_stat`` shows the merge type of the
> +process. Valid values are ``none``, ``madvise`` and ``process``.
> +
>  Monitoring KSM events
>  =====================
>  

The change LGTM.

-- 
An old man doll... just what I always wanted! - Clara

[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 228 bytes --]

[RESEND RFC PATCH v1 16/20] tools: add new prctl flags to prctl in tools dir

[Stefan Roesch]

This adds the new prctl flags to the include file prct.h in the tools
directory. This makes sure they are available for testing.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/include/uapi/linux/prctl.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/tools/include/uapi/linux/prctl.h b/tools/include/uapi/linux/prctl.h
index a5e06dcbba13..b8ba85f18e43 100644
--- a/tools/include/uapi/linux/prctl.h
+++ b/tools/include/uapi/linux/prctl.h
@@ -284,4 +284,6 @@ struct prctl_mm_map {
 #define PR_SET_VMA		0x53564d41
 # define PR_SET_VMA_ANON_NAME		0
 
+#define PR_SET_MEMORY_MERGE		65
+#define PR_GET_MEMORY_MERGE		66
 #endif /* _LINUX_PRCTL_H */
-- 
2.30.2

[RESEND RFC PATCH v1 17/20] selftests/vm: add KSM prctl merge test

[Stefan Roesch]

This adds the -t option to the ksm_tests program. The -t flag allows to
specify if it should use madvise or prctl ksm merging.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/testing/selftests/vm/Makefile    |   3 +-
 tools/testing/selftests/vm/ksm_tests.c | 116 +++++++++++++++++--------
 2 files changed, 80 insertions(+), 39 deletions(-)

diff --git a/tools/testing/selftests/vm/Makefile b/tools/testing/selftests/vm/Makefile
index 89c14e41bd43..8a50802d8700 100644
--- a/tools/testing/selftests/vm/Makefile
+++ b/tools/testing/selftests/vm/Makefile
@@ -25,7 +25,8 @@ MACHINE ?= $(shell echo $(uname_M) | sed -e 's/aarch64.*/arm64/' -e 's/ppc64.*/p
 # LDLIBS.
 MAKEFLAGS += --no-builtin-rules
 
-CFLAGS = -Wall -I $(top_srcdir) -I $(top_srcdir)/usr/include $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
+CFLAGS = -Wall -I $(top_srcdir)/tools/include/uapi
+CFLAGS += -I $(top_srcdir) -I $(top_srcdir)/usr/include $(EXTRA_CFLAGS) $(KHDR_INCLUDES)
 LDLIBS = -lrt -lpthread
 TEST_GEN_FILES = cow
 TEST_GEN_FILES += compaction_test
diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index f9eb4d67e0dd..386a0929c8a3 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: GPL-2.0
 
 #include <sys/mman.h>
+#include <sys/prctl.h>
+#include <sys/wait.h>
 #include <stdbool.h>
 #include <time.h>
 #include <string.h>
@@ -21,6 +23,7 @@
 #define KSM_PROT_STR_DEFAULT "rw"
 #define KSM_USE_ZERO_PAGES_DEFAULT false
 #define KSM_MERGE_ACROSS_NODES_DEFAULT true
+#define KSM_MERGE_TYPE_DEFAULT 0
 #define MB (1ul << 20)
 
 struct ksm_sysfs {
@@ -33,6 +36,12 @@ struct ksm_sysfs {
 	unsigned long use_zero_pages;
 };
 
+enum ksm_merge_type {
+	KSM_MERGE_MADVISE,
+	KSM_MERGE_PRCTL,
+	KSM_MERGE_LAST = KSM_MERGE_PRCTL
+};
+
 enum ksm_test_name {
 	CHECK_KSM_MERGE,
 	CHECK_KSM_UNMERGE,
@@ -129,6 +138,10 @@ static void print_help(void)
 	printf(" -m: change merge_across_nodes tunable\n"
 	       "     Default: %d\n", KSM_MERGE_ACROSS_NODES_DEFAULT);
 	printf(" -s: the size of duplicated memory area (in MiB)\n");
+	printf(" -t: KSM merge type\n"
+	       "     Default: 0\n"
+	       "     0: madvise merging\n"
+	       "     1: prctl merging\n");
 
 	exit(0);
 }
@@ -176,12 +189,21 @@ static int ksm_do_scan(int scan_count, struct timespec start_time, int timeout)
 	return 0;
 }
 
-static int ksm_merge_pages(void *addr, size_t size, struct timespec start_time, int timeout)
+static int ksm_merge_pages(int merge_type, void *addr, size_t size,
+			struct timespec start_time, int timeout)
 {
-	if (madvise(addr, size, MADV_MERGEABLE)) {
-		perror("madvise");
-		return 1;
+	if (merge_type == KSM_MERGE_MADVISE) {
+		if (madvise(addr, size, MADV_MERGEABLE)) {
+			perror("madvise");
+			return 1;
+		}
+	} else if (merge_type == KSM_MERGE_PRCTL) {
+		if (prctl(PR_SET_MEMORY_MERGE, 1)) {
+			perror("prctl");
+			return 1;
+		}
 	}
+
 	if (ksm_write_sysfs(KSM_FP("run"), 1))
 		return 1;
 
@@ -266,7 +288,8 @@ static int ksm_restore(struct ksm_sysfs *ksm_sysfs)
 	return 0;
 }
 
-static int check_ksm_merge(int mapping, int prot, long page_count, int timeout, size_t page_size)
+static int check_ksm_merge(int merge_type, int mapping, int prot,
+			long page_count, int timeout, size_t page_size)
 {
 	void *map_ptr;
 	struct timespec start_time;
@@ -281,13 +304,16 @@ static int check_ksm_merge(int mapping, int prot, long page_count, int timeout,
 	if (!map_ptr)
 		return KSFT_FAIL;
 
-	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
 		goto err_out;
 
 	/* verify that the right number of pages are merged */
 	if (assert_ksm_pages_count(page_count)) {
 		printf("OK\n");
-		munmap(map_ptr, page_size * page_count);
+		if (merge_type == KSM_MERGE_MADVISE)
+			munmap(map_ptr, page_size * page_count);
+		else if (merge_type == KSM_MERGE_PRCTL)
+			prctl(PR_SET_MEMORY_MERGE, 0);
 		return KSFT_PASS;
 	}
 
@@ -297,7 +323,7 @@ static int check_ksm_merge(int mapping, int prot, long page_count, int timeout,
 	return KSFT_FAIL;
 }
 
-static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_size)
+static int check_ksm_unmerge(int merge_type, int mapping, int prot, int timeout, size_t page_size)
 {
 	void *map_ptr;
 	struct timespec start_time;
@@ -313,7 +339,7 @@ static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_siz
 	if (!map_ptr)
 		return KSFT_FAIL;
 
-	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
 		goto err_out;
 
 	/* change 1 byte in each of the 2 pages -- KSM must automatically unmerge them */
@@ -337,8 +363,8 @@ static int check_ksm_unmerge(int mapping, int prot, int timeout, size_t page_siz
 	return KSFT_FAIL;
 }
 
-static int check_ksm_zero_page_merge(int mapping, int prot, long page_count, int timeout,
-				     bool use_zero_pages, size_t page_size)
+static int check_ksm_zero_page_merge(int merge_type, int mapping, int prot, long page_count,
+				int timeout, bool use_zero_pages, size_t page_size)
 {
 	void *map_ptr;
 	struct timespec start_time;
@@ -356,7 +382,7 @@ static int check_ksm_zero_page_merge(int mapping, int prot, long page_count, int
 	if (!map_ptr)
 		return KSFT_FAIL;
 
-	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
 		goto err_out;
 
        /*
@@ -402,8 +428,8 @@ static int get_first_mem_node(void)
 	return get_next_mem_node(numa_max_node());
 }
 
-static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_across_nodes,
-				size_t page_size)
+static int check_ksm_numa_merge(int merge_type, int mapping, int prot, int timeout,
+				bool merge_across_nodes, size_t page_size)
 {
 	void *numa1_map_ptr, *numa2_map_ptr;
 	struct timespec start_time;
@@ -439,8 +465,8 @@ static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_a
 	memset(numa2_map_ptr, '*', page_size);
 
 	/* try to merge the pages */
-	if (ksm_merge_pages(numa1_map_ptr, page_size, start_time, timeout) ||
-	    ksm_merge_pages(numa2_map_ptr, page_size, start_time, timeout))
+	if (ksm_merge_pages(merge_type, numa1_map_ptr, page_size, start_time, timeout) ||
+	    ksm_merge_pages(merge_type, numa2_map_ptr, page_size, start_time, timeout))
 		goto err_out;
 
        /*
@@ -466,7 +492,8 @@ static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_a
 	return KSFT_FAIL;
 }
 
-static int ksm_merge_hugepages_time(int mapping, int prot, int timeout, size_t map_size)
+static int ksm_merge_hugepages_time(int merge_type, int mapping, int prot,
+				int timeout, size_t map_size)
 {
 	void *map_ptr, *map_ptr_orig;
 	struct timespec start_time, end_time;
@@ -508,7 +535,7 @@ static int ksm_merge_hugepages_time(int mapping, int prot, int timeout, size_t m
 		perror("clock_gettime");
 		goto err_out;
 	}
-	if (ksm_merge_pages(map_ptr, map_size, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, map_size, start_time, timeout))
 		goto err_out;
 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &end_time)) {
 		perror("clock_gettime");
@@ -533,7 +560,7 @@ static int ksm_merge_hugepages_time(int mapping, int prot, int timeout, size_t m
 	return KSFT_FAIL;
 }
 
-static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size)
+static int ksm_merge_time(int merge_type, int mapping, int prot, int timeout, size_t map_size)
 {
 	void *map_ptr;
 	struct timespec start_time, end_time;
@@ -549,7 +576,7 @@ static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size)
 		perror("clock_gettime");
 		goto err_out;
 	}
-	if (ksm_merge_pages(map_ptr, map_size, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, map_size, start_time, timeout))
 		goto err_out;
 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &end_time)) {
 		perror("clock_gettime");
@@ -574,7 +601,7 @@ static int ksm_merge_time(int mapping, int prot, int timeout, size_t map_size)
 	return KSFT_FAIL;
 }
 
-static int ksm_unmerge_time(int mapping, int prot, int timeout, size_t map_size)
+static int ksm_unmerge_time(int merge_type, int mapping, int prot, int timeout, size_t map_size)
 {
 	void *map_ptr;
 	struct timespec start_time, end_time;
@@ -589,7 +616,7 @@ static int ksm_unmerge_time(int mapping, int prot, int timeout, size_t map_size)
 		perror("clock_gettime");
 		goto err_out;
 	}
-	if (ksm_merge_pages(map_ptr, map_size, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, map_size, start_time, timeout))
 		goto err_out;
 
 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
@@ -621,7 +648,7 @@ static int ksm_unmerge_time(int mapping, int prot, int timeout, size_t map_size)
 	return KSFT_FAIL;
 }
 
-static int ksm_cow_time(int mapping, int prot, int timeout, size_t page_size)
+static int ksm_cow_time(int merge_type, int mapping, int prot, int timeout, size_t page_size)
 {
 	void *map_ptr;
 	struct timespec start_time, end_time;
@@ -660,7 +687,7 @@ static int ksm_cow_time(int mapping, int prot, int timeout, size_t page_size)
 		memset(map_ptr + page_size * i, '+', i / 2 + 1);
 		memset(map_ptr + page_size * (i + 1), '+', i / 2 + 1);
 	}
-	if (ksm_merge_pages(map_ptr, page_size * page_count, start_time, timeout))
+	if (ksm_merge_pages(merge_type, map_ptr, page_size * page_count, start_time, timeout))
 		goto err_out;
 
 	if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
@@ -697,6 +724,7 @@ int main(int argc, char *argv[])
 	int ret, opt;
 	int prot = 0;
 	int ksm_scan_limit_sec = KSM_SCAN_LIMIT_SEC_DEFAULT;
+	int merge_type = KSM_MERGE_TYPE_DEFAULT;
 	long page_count = KSM_PAGE_COUNT_DEFAULT;
 	size_t page_size = sysconf(_SC_PAGESIZE);
 	struct ksm_sysfs ksm_sysfs_old;
@@ -705,7 +733,7 @@ int main(int argc, char *argv[])
 	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
 	long size_MB = 0;
 
-	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:MUZNPCHD")) != -1) {
+	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:MUZNPCHD")) != -1) {
 		switch (opt) {
 		case 'a':
 			prot = str_to_prot(optarg);
@@ -745,6 +773,17 @@ int main(int argc, char *argv[])
 				printf("Size must be greater than 0\n");
 				return KSFT_FAIL;
 			}
+		case 't':
+			{
+				int tmp = atoi(optarg);
+
+				if (tmp < 0 || tmp > KSM_MERGE_LAST) {
+					printf("Invalid merge type\n");
+					return KSFT_FAIL;
+				}
+				merge_type = atoi(optarg);
+			}
+			break;
 		case 'M':
 			break;
 		case 'U':
@@ -795,35 +834,36 @@ int main(int argc, char *argv[])
 
 	switch (test_name) {
 	case CHECK_KSM_MERGE:
-		ret = check_ksm_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
+		ret = check_ksm_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
 				      ksm_scan_limit_sec, page_size);
 		break;
 	case CHECK_KSM_UNMERGE:
-		ret = check_ksm_unmerge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
-					page_size);
+		ret = check_ksm_unmerge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
+					ksm_scan_limit_sec, page_size);
 		break;
 	case CHECK_KSM_ZERO_PAGE_MERGE:
-		ret = check_ksm_zero_page_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
-						ksm_scan_limit_sec, use_zero_pages, page_size);
+		ret = check_ksm_zero_page_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
+						page_count, ksm_scan_limit_sec, use_zero_pages,
+						page_size);
 		break;
 	case CHECK_KSM_NUMA_MERGE:
-		ret = check_ksm_numa_merge(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
-					   merge_across_nodes, page_size);
+		ret = check_ksm_numa_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
+					ksm_scan_limit_sec, merge_across_nodes, page_size);
 		break;
 	case KSM_MERGE_TIME:
 		if (size_MB == 0) {
 			printf("Option '-s' is required.\n");
 			return KSFT_FAIL;
 		}
-		ret = ksm_merge_time(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
-				     size_MB);
+		ret = ksm_merge_time(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
+				ksm_scan_limit_sec, size_MB);
 		break;
 	case KSM_MERGE_TIME_HUGE_PAGES:
 		if (size_MB == 0) {
 			printf("Option '-s' is required.\n");
 			return KSFT_FAIL;
 		}
-		ret = ksm_merge_hugepages_time(MAP_PRIVATE | MAP_ANONYMOUS, prot,
+		ret = ksm_merge_hugepages_time(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 				ksm_scan_limit_sec, size_MB);
 		break;
 	case KSM_UNMERGE_TIME:
@@ -831,12 +871,12 @@ int main(int argc, char *argv[])
 			printf("Option '-s' is required.\n");
 			return KSFT_FAIL;
 		}
-		ret = ksm_unmerge_time(MAP_PRIVATE | MAP_ANONYMOUS, prot,
+		ret = ksm_unmerge_time(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 				       ksm_scan_limit_sec, size_MB);
 		break;
 	case KSM_COW_TIME:
-		ret = ksm_cow_time(MAP_PRIVATE | MAP_ANONYMOUS, prot, ksm_scan_limit_sec,
-				   page_size);
+		ret = ksm_cow_time(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
+				ksm_scan_limit_sec, page_size);
 		break;
 	}
 
-- 
2.30.2

[RESEND RFC PATCH v1 18/20] selftests/vm: add KSM get merge type test

[Stefan Roesch]

This adds the -G flag to the ksm_tests to query if prctl has been used
to enable ksm merging.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/testing/selftests/vm/ksm_tests.c | 37 ++++++++++++++++++++++++--
 1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index 386a0929c8a3..9667cb3b8c6a 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -45,6 +45,7 @@ enum ksm_merge_type {
 enum ksm_test_name {
 	CHECK_KSM_MERGE,
 	CHECK_KSM_UNMERGE,
+	CHECK_KSM_GET_MERGE_TYPE,
 	CHECK_KSM_ZERO_PAGE_MERGE,
 	CHECK_KSM_NUMA_MERGE,
 	KSM_MERGE_TIME,
@@ -124,7 +125,8 @@ static void print_help(void)
 	       " -D evaluate unmerging time and speed when disabling KSM.\n"
 	       "    For this test, the size of duplicated memory area (in MiB)\n"
 	       "    must be provided using -s option\n"
-	       " -C evaluate the time required to break COW of merged pages.\n\n");
+	       " -C evaluate the time required to break COW of merged pages.\n"
+	       " -G query merge mode\n\n");
 
 	printf(" -a: specify the access protections of pages.\n"
 	       "     <prot> must be of the form [rwx].\n"
@@ -323,6 +325,31 @@ static int check_ksm_merge(int merge_type, int mapping, int prot,
 	return KSFT_FAIL;
 }
 
+static int check_ksm_get_merge_type(void)
+{
+	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
+		perror("prctl set");
+		return 1;
+	}
+
+	int is_on = prctl(PR_GET_MEMORY_MERGE, 0);
+
+	if (prctl(PR_SET_MEMORY_MERGE, 0)) {
+		perror("prctl set");
+		return 1;
+	}
+
+	int is_off = prctl(PR_GET_MEMORY_MERGE, 0);
+
+	if (is_on && is_off) {
+		printf("OK\n");
+		return KSFT_PASS;
+	}
+
+	printf("Not OK\n");
+	return KSFT_FAIL;
+}
+
 static int check_ksm_unmerge(int merge_type, int mapping, int prot, int timeout, size_t page_size)
 {
 	void *map_ptr;
@@ -733,7 +760,7 @@ int main(int argc, char *argv[])
 	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
 	long size_MB = 0;
 
-	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:MUZNPCHD")) != -1) {
+	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:GMUZNPCHD")) != -1) {
 		switch (opt) {
 		case 'a':
 			prot = str_to_prot(optarg);
@@ -792,6 +819,9 @@ int main(int argc, char *argv[])
 		case 'Z':
 			test_name = CHECK_KSM_ZERO_PAGE_MERGE;
 			break;
+		case 'G':
+			test_name = CHECK_KSM_GET_MERGE_TYPE;
+			break;
 		case 'N':
 			test_name = CHECK_KSM_NUMA_MERGE;
 			break;
@@ -841,6 +871,9 @@ int main(int argc, char *argv[])
 		ret = check_ksm_unmerge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 					ksm_scan_limit_sec, page_size);
 		break;
+	case CHECK_KSM_GET_MERGE_TYPE:
+		ret = check_ksm_get_merge_type();
+		break;
 	case CHECK_KSM_ZERO_PAGE_MERGE:
 		ret = check_ksm_zero_page_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 						page_count, ksm_scan_limit_sec, use_zero_pages,
-- 
2.30.2

[RESEND RFC PATCH v1 19/20] selftests/vm: add KSM fork test

[Stefan Roesch]

Add fork test to verify that the MMF_VM_MERGE_ANY flag is inherited by
the child process.

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/testing/selftests/vm/ksm_tests.c | 53 +++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index 9667cb3b8c6a..a0a48ac43b29 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -44,6 +44,7 @@ enum ksm_merge_type {
 
 enum ksm_test_name {
 	CHECK_KSM_MERGE,
+	CHECK_KSM_MERGE_FORK,
 	CHECK_KSM_UNMERGE,
 	CHECK_KSM_GET_MERGE_TYPE,
 	CHECK_KSM_ZERO_PAGE_MERGE,
@@ -126,7 +127,8 @@ static void print_help(void)
 	       "    For this test, the size of duplicated memory area (in MiB)\n"
 	       "    must be provided using -s option\n"
 	       " -C evaluate the time required to break COW of merged pages.\n"
-	       " -G query merge mode\n\n");
+	       " -G query merge mode\n"
+	       " -F evaluate that the KSM process flag is inherited\n\n");
 
 	printf(" -a: specify the access protections of pages.\n"
 	       "     <prot> must be of the form [rwx].\n"
@@ -325,6 +327,47 @@ static int check_ksm_merge(int merge_type, int mapping, int prot,
 	return KSFT_FAIL;
 }
 
+/* Verify that prctl ksm flag is inherited. */
+static int check_ksm_fork(void)
+{
+	int rc = KSFT_FAIL;
+	pid_t child_pid;
+
+	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
+		perror("prctl");
+		return KSFT_FAIL;
+	}
+
+	child_pid = fork();
+	if (child_pid == 0) {
+		int is_on = prctl(PR_GET_MEMORY_MERGE, 0);
+
+		if (!is_on)
+			exit(KSFT_FAIL);
+
+		exit(KSFT_PASS);
+	}
+
+	if (child_pid < 0)
+		goto out;
+
+	if (waitpid(child_pid, &rc, 0) < 0)
+		rc = KSFT_FAIL;
+
+	if (prctl(PR_SET_MEMORY_MERGE, 0)) {
+		perror("prctl");
+		rc = KSFT_FAIL;
+	}
+
+out:
+	if (rc == KSFT_PASS)
+		printf("OK\n");
+	else
+		printf("Not OK\n");
+
+	return rc;
+}
+
 static int check_ksm_get_merge_type(void)
 {
 	if (prctl(PR_SET_MEMORY_MERGE, 1)) {
@@ -760,7 +803,7 @@ int main(int argc, char *argv[])
 	bool merge_across_nodes = KSM_MERGE_ACROSS_NODES_DEFAULT;
 	long size_MB = 0;
 
-	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:GMUZNPCHD")) != -1) {
+	while ((opt = getopt(argc, argv, "ha:p:l:z:m:s:t:FGMUZNPCHD")) != -1) {
 		switch (opt) {
 		case 'a':
 			prot = str_to_prot(optarg);
@@ -811,6 +854,9 @@ int main(int argc, char *argv[])
 				merge_type = atoi(optarg);
 			}
 			break;
+		case 'F':
+			test_name = CHECK_KSM_MERGE_FORK;
+			break;
 		case 'M':
 			break;
 		case 'U':
@@ -867,6 +913,9 @@ int main(int argc, char *argv[])
 		ret = check_ksm_merge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot, page_count,
 				      ksm_scan_limit_sec, page_size);
 		break;
+	case CHECK_KSM_MERGE_FORK:
+		ret = check_ksm_fork();
+		break;
 	case CHECK_KSM_UNMERGE:
 		ret = check_ksm_unmerge(merge_type, MAP_PRIVATE | MAP_ANONYMOUS, prot,
 					ksm_scan_limit_sec, page_size);
-- 
2.30.2

[RESEND RFC PATCH v1 20/20] selftests/vm: add two functions for debugging merge outcome

[Stefan Roesch]

This adds two functions to report the metrics in /proc/self/ksm_stat and
/sys/kernel/debug/mm/ksm.

The debugging can be enabled with the following command line:
make -C tools/testing/selftests TARGETS="vm" --keep-going \
        EXTRA_CFLAGS=-DDEBUG=1

Signed-off-by: Stefan Roesch <shr@devkernel.io>
---
 tools/testing/selftests/vm/ksm_tests.c | 54 ++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)

diff --git a/tools/testing/selftests/vm/ksm_tests.c b/tools/testing/selftests/vm/ksm_tests.c
index a0a48ac43b29..9fb21b982dc9 100644
--- a/tools/testing/selftests/vm/ksm_tests.c
+++ b/tools/testing/selftests/vm/ksm_tests.c
@@ -93,6 +93,55 @@ static int ksm_read_sysfs(const char *file_path, unsigned long *val)
 	return 0;
 }
 
+#ifdef DEBUG
+static void ksm_print_sysfs(void)
+{
+	unsigned long max_page_sharing, pages_sharing, pages_shared;
+	unsigned long full_scans, pages_unshared, pages_volatile;
+	unsigned long stable_node_chains, stable_node_dups;
+	long general_profit;
+
+	if (ksm_read_sysfs(KSM_FP("pages_shared"), &pages_shared) ||
+	    ksm_read_sysfs(KSM_FP("pages_sharing"), &pages_sharing) ||
+	    ksm_read_sysfs(KSM_FP("max_page_sharing"), &max_page_sharing) ||
+	    ksm_read_sysfs(KSM_FP("full_scans"), &full_scans) ||
+	    ksm_read_sysfs(KSM_FP("pages_unshared"), &pages_unshared) ||
+	    ksm_read_sysfs(KSM_FP("pages_volatile"), &pages_volatile) ||
+	    ksm_read_sysfs(KSM_FP("stable_node_chains"), &stable_node_chains) ||
+	    ksm_read_sysfs(KSM_FP("stable_node_dups"), &stable_node_dups) ||
+	    ksm_read_sysfs(KSM_FP("general_profit"), (unsigned long *)&general_profit))
+		return;
+
+	printf("pages_shared      : %lu\n", pages_shared);
+	printf("pages_sharing     : %lu\n", pages_sharing);
+	printf("max_page_sharing  : %lu\n", max_page_sharing);
+	printf("full_scans        : %lu\n", full_scans);
+	printf("pages_unshared    : %lu\n", pages_unshared);
+	printf("pages_volatile    : %lu\n", pages_volatile);
+	printf("stable_node_chains: %lu\n", stable_node_chains);
+	printf("stable_node_dups  : %lu\n", stable_node_dups);
+	printf("general_profit    : %ld\n", general_profit);
+}
+
+static void ksm_print_procfs(void)
+{
+	const char *file_name = "/proc/self/ksm_stat";
+	char buffer[512];
+	FILE *f = fopen(file_name, "r");
+
+	if (!f) {
+		fprintf(stderr, "f %s\n", file_name);
+		perror("fopen");
+		return;
+	}
+
+	while (fgets(buffer, sizeof(buffer), f))
+		printf("%s", buffer);
+
+	fclose(f);
+}
+#endif
+
 static int str_to_prot(char *prot_str)
 {
 	int prot = 0;
@@ -237,6 +286,11 @@ static bool assert_ksm_pages_count(long dupl_page_count)
 	    ksm_read_sysfs(KSM_FP("max_page_sharing"), &max_page_sharing))
 		return false;
 
+#ifdef DEBUG
+	ksm_print_sysfs();
+	ksm_print_procfs();
+#endif
+
 	/*
 	 * Since there must be at least 2 pages for merging and 1 page can be
 	 * shared with the limited number of pages (max_page_sharing), sometimes
-- 
2.30.2

Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[David Hildenbrand]

On 23.01.23 18:37, Stefan Roesch wrote:
> So far KSM can only be enabled by calling madvise for memory regions. What is
> required to enable KSM for more workloads is to enable / disable it at the
> process / cgroup level.

Did you stumble over the proposals from last year to enable this 
per-process [1] and system-wide [2]? I remember there was also regarding 
enabling it system-wide.

I'm going to point out the security aspect, and that e.g., Windows used 
to enable it system-wide before getting taught by security experts 
otherwise. Details on KSM and security aspects can be found in that thread.

Long story short: one has to be very careful with that and only enable 
it for very carefully selected worklads. Letting a workload opt-in on a 
VMA level is most probably safer than an admin blindly turning this on 
for random processes ...

Last attempts got nacked ...

[1] 
https://lore.kernel.org/all/20220517092701.1662641-1-xu.xin16@zte.com.cn/
[2] https://lore.kernel.org/all/20220609055658.703472-1-xu.xin16@zte.com.cn/

> 
> 1. New options for prctl system command
> This patch series adds two new options to the prctl system call. The first
> one allows to enable KSM at the process level and the second one to query the
> setting.
> 
> The setting will be inherited by child processes.
> 
> With the above setting, KSM can be enabled for the seed process of a cgroup
> and all processes in the cgroup will inherit the setting.
> 
> 2. Changes to KSM processing
> When KSM is enabled at the process level, the KSM code will iterate over all
> the VMA's and enable KSM for the eligible VMA's.
> 
> When forking a process that has KSM enabled, the setting will be inherited by
> the new child process.
> 
> In addition when KSM is disabled for a process, KSM will be disabled for the
> VMA's where KSM has been enabled.
> 
> 3. Add tracepoints to KSM
> Currently KSM has no tracepoints. This adds tracepoints to the key KSM functions
> to make it easier to debug KSM.
> 
> 4. Add general_profit metric
> The general_profit metric of KSM is specified in the documentation, but not
> calculated. This adds the general profit metric to /sys/kernel/debug/mm/ksm.
> 
> 5. Add more metrics to ksm_stat
> This adds the process profit and ksm type metric to /proc/<pid>/ksm_stat.
> 
> 6. Add more tests to ksm_tests
> This adds an option to specify the merge type to the ksm_tests. This allows to
> test madvise and prctl KSM. It also adds a new option to query if prctl KSM has
> been enabled. It adds a fork test to verify that the KSM process setting is
> inherited by client processes.
> 
> 
> Stefan Roesch (20):
>    mm: add new flag to enable ksm per process
>    mm: add flag to __ksm_enter
>    mm: add flag to __ksm_exit call
>    mm: invoke madvise for all vmas in scan_get_next_rmap_item
>    mm: support disabling of ksm for a process
>    mm: add new prctl option to get and set ksm for a process
>    mm: add tracepoints to ksm
>    mm: split off pages_volatile function
>    mm: expose general_profit metric
>    docs: document general_profit sysfs knob
>    mm: calculate ksm process profit metric
>    mm: add ksm_merge_type() function
>    mm: expose ksm process profit metric in ksm_stat
>    mm: expose ksm merge type in ksm_stat
>    docs: document new procfs ksm knobs
>    tools: add new prctl flags to prctl in tools dir
>    selftests/vm: add KSM prctl merge test
>    selftests/vm: add KSM get merge type test
>    selftests/vm: add KSM fork test
>    selftests/vm: add two functions for debugging merge outcome
> 
>   Documentation/ABI/testing/sysfs-kernel-mm-ksm |   8 +
>   Documentation/admin-guide/mm/ksm.rst          |   8 +-
>   MAINTAINERS                                   |   1 +
>   fs/proc/base.c                                |   5 +
>   include/linux/ksm.h                           |  19 +-
>   include/linux/sched/coredump.h                |   1 +
>   include/trace/events/ksm.h                    | 257 ++++++++++++++++++
>   include/uapi/linux/prctl.h                    |   2 +
>   kernel/sys.c                                  |  29 ++
>   mm/ksm.c                                      | 134 ++++++++-
>   tools/include/uapi/linux/prctl.h              |   2 +
>   tools/testing/selftests/vm/Makefile           |   3 +-
>   tools/testing/selftests/vm/ksm_tests.c        | 254 ++++++++++++++---
>   13 files changed, 665 insertions(+), 58 deletions(-)
>   create mode 100644 include/trace/events/ksm.h
> 
> 
> base-commit: c1649ec55708ae42091a2f1bca1ab49ecd722d55

-- 
Thanks,

David / dhildenb

Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[Stefan Roesch]

David Hildenbrand <david@redhat.com> writes:

> On 23.01.23 18:37, Stefan Roesch wrote:
>> So far KSM can only be enabled by calling madvise for memory regions. What is
>> required to enable KSM for more workloads is to enable / disable it at the
>> process / cgroup level.
>
> Did you stumble over the proposals from last year to enable this per-process [1]
> and system-wide [2]? I remember there was also regarding enabling it
> system-wide.
>
I saw the earlier proposals. Enabling it at the system level doesn't
seem to be the right choice. You generally want to enable it at a more
fine-grained level. Therefore this enables it at the process level with
prctl.

> I'm going to point out the security aspect, and that e.g., Windows used to
> enable it system-wide before getting taught by security experts otherwise.
> Details on KSM and security aspects can be found in that thread.
>
If I'm not mistaken the security aspect exists today. When KSM is
enabled with madvise this is the same.

> Long story short: one has to be very careful with that and only enable it for
> very carefully selected worklads. Letting a workload opt-in on a VMA level is
> most probably safer than an admin blindly turning this on for random processes
> ...
>
Thats why this is enabled with prctl. Its a deliberate choice to enable
it for a process.

> Last attempts got nacked ...
>
> [1] https://lore.kernel.org/all/20220517092701.1662641-1-xu.xin16@zte.com.cn/
> [2] https://lore.kernel.org/all/20220609055658.703472-1-xu.xin16@zte.com.cn/
>
My understanding is that there were problems with the patch and how it
exposed KSM. The other objection was the enable-all configuration
option.

>> 1. New options for prctl system command
>> This patch series adds two new options to the prctl system call. The first
>> one allows to enable KSM at the process level and the second one to query the
>> setting.
>> The setting will be inherited by child processes.
>> With the above setting, KSM can be enabled for the seed process of a cgroup
>> and all processes in the cgroup will inherit the setting.
>> 2. Changes to KSM processing
>> When KSM is enabled at the process level, the KSM code will iterate over all
>> the VMA's and enable KSM for the eligible VMA's.
>> When forking a process that has KSM enabled, the setting will be inherited by
>> the new child process.
>> In addition when KSM is disabled for a process, KSM will be disabled for the
>> VMA's where KSM has been enabled.
>> 3. Add tracepoints to KSM
>> Currently KSM has no tracepoints. This adds tracepoints to the key KSM functions
>> to make it easier to debug KSM.
>> 4. Add general_profit metric
>> The general_profit metric of KSM is specified in the documentation, but not
>> calculated. This adds the general profit metric to /sys/kernel/debug/mm/ksm.
>> 5. Add more metrics to ksm_stat
>> This adds the process profit and ksm type metric to /proc/<pid>/ksm_stat.
>> 6. Add more tests to ksm_tests
>> This adds an option to specify the merge type to the ksm_tests. This allows to
>> test madvise and prctl KSM. It also adds a new option to query if prctl KSM has
>> been enabled. It adds a fork test to verify that the KSM process setting is
>> inherited by client processes.
>> Stefan Roesch (20):
>>    mm: add new flag to enable ksm per process
>>    mm: add flag to __ksm_enter
>>    mm: add flag to __ksm_exit call
>>    mm: invoke madvise for all vmas in scan_get_next_rmap_item
>>    mm: support disabling of ksm for a process
>>    mm: add new prctl option to get and set ksm for a process
>>    mm: add tracepoints to ksm
>>    mm: split off pages_volatile function
>>    mm: expose general_profit metric
>>    docs: document general_profit sysfs knob
>>    mm: calculate ksm process profit metric
>>    mm: add ksm_merge_type() function
>>    mm: expose ksm process profit metric in ksm_stat
>>    mm: expose ksm merge type in ksm_stat
>>    docs: document new procfs ksm knobs
>>    tools: add new prctl flags to prctl in tools dir
>>    selftests/vm: add KSM prctl merge test
>>    selftests/vm: add KSM get merge type test
>>    selftests/vm: add KSM fork test
>>    selftests/vm: add two functions for debugging merge outcome
>>   Documentation/ABI/testing/sysfs-kernel-mm-ksm |   8 +
>>   Documentation/admin-guide/mm/ksm.rst          |   8 +-
>>   MAINTAINERS                                   |   1 +
>>   fs/proc/base.c                                |   5 +
>>   include/linux/ksm.h                           |  19 +-
>>   include/linux/sched/coredump.h                |   1 +
>>   include/trace/events/ksm.h                    | 257 ++++++++++++++++++
>>   include/uapi/linux/prctl.h                    |   2 +
>>   kernel/sys.c                                  |  29 ++
>>   mm/ksm.c                                      | 134 ++++++++-
>>   tools/include/uapi/linux/prctl.h              |   2 +
>>   tools/testing/selftests/vm/Makefile           |   3 +-
>>   tools/testing/selftests/vm/ksm_tests.c        | 254 ++++++++++++++---
>>   13 files changed, 665 insertions(+), 58 deletions(-)
>>   create mode 100644 include/trace/events/ksm.h
>> base-commit: c1649ec55708ae42091a2f1bca1ab49ecd722d55

Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[David Hildenbrand]

[...]

>> I'm going to point out the security aspect, and that e.g., Windows used to
>> enable it system-wide before getting taught by security experts otherwise.
>> Details on KSM and security aspects can be found in that thread.
>>
> If I'm not mistaken the security aspect exists today. When KSM is
> enabled with madvise this is the same.

Yes, and we mostly only use it for virtual machines -- and to be 
precise, guest memory only -- where it has to be enabled explicitly on a 
well documented basis ...

Impossible for an admin to force it on other parts of the hypervisor 
process that might be more security sensitive. Or on other arbitrary 
applications, for now.

> 
>> Long story short: one has to be very careful with that and only enable it for
>> very carefully selected worklads. Letting a workload opt-in on a VMA level is
>> most probably safer than an admin blindly turning this on for random processes
>> ... >>
[...]

>>
>> [1] https://lore.kernel.org/all/20220517092701.1662641-1-xu.xin16@zte.com.cn/
>> [2] https://lore.kernel.org/all/20220609055658.703472-1-xu.xin16@zte.com.cn/
>>
> My understanding is that there were problems with the patch and how it
> exposed KSM. The other objection was the enable-all configuration
> option.

I don't remember all the discussions, but one concern was how to handle 
processes that deliberately want to disable it on some parts of memory.

Anyhow, I cc'ed the relevant parties already.

-- 
Thanks,

David / dhildenb

Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[Michal Hocko]

On Tue 24-01-23 19:01:49, David Hildenbrand wrote:
> [...]
> 
> > > I'm going to point out the security aspect, and that e.g., Windows used to
> > > enable it system-wide before getting taught by security experts otherwise.
> > > Details on KSM and security aspects can be found in that thread.
> > > 
> > If I'm not mistaken the security aspect exists today. When KSM is
> > enabled with madvise this is the same.
> 
> Yes, and we mostly only use it for virtual machines -- and to be precise,
> guest memory only -- where it has to be enabled explicitly on a well
> documented basis ...
> 
> Impossible for an admin to force it on other parts of the hypervisor process
> that might be more security sensitive. Or on other arbitrary applications,
> for now.
> 
> > 
> > > Long story short: one has to be very careful with that and only enable it for
> > > very carefully selected worklads. Letting a workload opt-in on a VMA level is
> > > most probably safer than an admin blindly turning this on for random processes
> > > ... >>
> [...]
> 
> > > 
> > > [1] https://lore.kernel.org/all/20220517092701.1662641-1-xu.xin16@zte.com.cn/
> > > [2] https://lore.kernel.org/all/20220609055658.703472-1-xu.xin16@zte.com.cn/
> > > 
> > My understanding is that there were problems with the patch and how it
> > exposed KSM. The other objection was the enable-all configuration
> > option.
> 
> I don't remember all the discussions, but one concern was how to handle
> processes that deliberately want to disable it on some parts of memory.
> 
> Anyhow, I cc'ed the relevant parties already.

Thanks! I do not remember all the details from the past discussion
except it was /proc and later global setting. Neither really were great
choices. We have discussed pidfd_madvise and prctl IIRC. For the latter
there was no real argument about when it is desirable to apply merging
on all existing vmas (e.g. is it really desirable on stack/brk or malloc
arenas or would user need to opt out for those).

I have read through your cover letter and it talks about the interface
but it doesn't really talk about usecases and how they are supposed to
use this feature - except the prctl based flag gets inherited. So could
you elaborate some more about those usecases please?
-- 
Michal Hocko
SUSE Labs

Re: [RESEND RFC PATCH v1 00/20] mm: process/cgroup ksm support

[Rik van Riel]

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On Wed, 2023-01-25 at 14:01 +0100, Michal Hocko wrote:
> 
> I have read through your cover letter and it talks about the
> interface
> but it doesn't really talk about usecases and how they are supposed
> to
> use this feature - except the prctl based flag gets inherited. So
> could
> you elaborate some more about those usecases please?

I can explain a little about the use case. There are people
who use forked (rather than threaded) servers for certain
workloads, from a garbage collected language without pointers,
which means madvise simply cannot be made available in that
language.

The people running that workload have experimented with uKSM
in the past, and seen about a 20% capacity increase from
doing that.

Because madvise is not possible in that programming language,
and the addresses of data keep moving around as things get
garbage collected, KSM sharing needs to be enabled "from the
outside" for that workload.

prctl seems like a good way to do that.

-- 
All Rights Reversed.

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Re: [RESEND RFC PATCH v1 07/20] mm: add tracepoints to ksm

[Steven Rostedt]

On Sun, 22 Jan 2023 21:00:29 -0800
Stefan Roesch <shr@devkernel.io> wrote:

> This adds the following tracepoints to ksm:
> - start / stop scan
> - ksm enter / exit
> - merge a page
> - merge a page with ksm
> - remove a page
> - remove a rmap item
> 
> Signed-off-by: Stefan Roesch <shr@devkernel.io>
> ---
>  MAINTAINERS                |   1 +
>  include/trace/events/ksm.h | 257 +++++++++++++++++++++++++++++++++++++
>  mm/ksm.c                   |  20 ++-
>  3 files changed, 276 insertions(+), 2 deletions(-)
>  create mode 100644 include/trace/events/ksm.h

From the tracing pov:

Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>

-- Steve