The patch titled
Subject: ksm: consider KSM-placed zeropages when calculating KSM profit
has been added to the -mm mm-unstable branch. Its filename is
ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: xu xin <xu.xin16@xxxxxxxxxx>
Subject: ksm: consider KSM-placed zeropages when calculating KSM profit
Date: Tue, 13 Jun 2023 11:09:42 +0800
When use_zero_pages is enabled, the calculation of ksm profit is not
correct because ksm zero pages is not counted in. So update the
calculation of KSM profit including the documentation.
Link: https://lkml.kernel.org/r/20230613030942.186041-1-yang.yang29@xxxxxxxxxx
Signed-off-by: xu xin <xu.xin16@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Xiaokai Ran <ran.xiaokai@xxxxxxxxxx>
Cc: Yang Yang <yang.yang29@xxxxxxxxxx>
Cc: Jiang Xuexin <jiang.xuexin@xxxxxxxxxx>
Cc: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/mm/ksm.rst | 18 +++++++++++-------
mm/ksm.c | 4 ++--
2 files changed, 13 insertions(+), 9 deletions(-)
--- a/Documentation/admin-guide/mm/ksm.rst~ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit
+++ a/Documentation/admin-guide/mm/ksm.rst
@@ -203,21 +203,25 @@ several times, which are unprofitable me
1) How to determine whether KSM save memory or consume memory in system-wide
range? Here is a simple approximate calculation for reference::
- general_profit =~ pages_sharing * sizeof(page) - (all_rmap_items) *
+ general_profit =~ ksm_saved_pages * sizeof(page) - (all_rmap_items) *
sizeof(rmap_item);
- where all_rmap_items can be easily obtained by summing ``pages_sharing``,
- ``pages_shared``, ``pages_unshared`` and ``pages_volatile``.
+ where ksm_saved_pages equals to the sum of ``pages_sharing`` +
+ ``ksm_zero_pages`` of the system, and all_rmap_items can be easily
+ obtained by summing ``pages_sharing``, ``pages_shared``, ``pages_unshared``
+ and ``pages_volatile``.
2) The KSM profit inner a single process can be similarly obtained by the
following approximate calculation::
- process_profit =~ ksm_merging_pages * sizeof(page) -
+ process_profit =~ ksm_saved_pages * sizeof(page) -
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``. The process profit
- is also shown in ``/proc/<pid>/ksm_stat`` as ksm_process_profit.
+ where ksm_saved_pages equals to the sum of ``ksm_merging_pages`` and
+ ``ksm_zero_pages``, both of which are shown under the directory
+ ``/proc/<pid>/ksm_stat``, and ksm_rmap_items is also 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
--- a/mm/ksm.c~ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit
+++ a/mm/ksm.c
@@ -3092,7 +3092,7 @@ static void wait_while_offlining(void)
#ifdef CONFIG_PROC_FS
long ksm_process_profit(struct mm_struct *mm)
{
- return mm->ksm_merging_pages * PAGE_SIZE -
+ return (long)(mm->ksm_merging_pages + mm->ksm_zero_pages) * PAGE_SIZE -
mm->ksm_rmap_items * sizeof(struct ksm_rmap_item);
}
#endif /* CONFIG_PROC_FS */
@@ -3373,7 +3373,7 @@ static ssize_t general_profit_show(struc
{
long general_profit;
- general_profit = ksm_pages_sharing * PAGE_SIZE -
+ general_profit = (ksm_pages_sharing + ksm_zero_pages) * PAGE_SIZE -
ksm_rmap_items * sizeof(struct ksm_rmap_item);
return sysfs_emit(buf, "%ld\n", general_profit);
_
Patches currently in -mm which might be from xu.xin16@xxxxxxxxxx are
ksm-support-unsharing-ksm-placed-zero-pages.patch
ksm-count-all-zero-pages-placed-by-ksm.patch
ksm-add-ksm-zero-pages-for-each-process.patch
ksm-consider-ksm-placed-zeropages-when-calculating-ksm-profit.patch
selftest-add-a-testcase-of-ksm-zero-pages.patch
