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mm/vmstat: add event for ksm swapping in copy

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When faults in from swap what used to be a KSM page and that page had been
swapped in before, system has to make a copy, and leaves remerging the
pages to a later pass of ksmd.

That is not good for performace, we'd better to reduce this kind of copy.
There are some ways to reduce it, for example lessen swappiness or
madvise(, , MADV_MERGEABLE) range.  So add this event to support doing
this tuning.  Just like this patch: "mm, THP, swap: add THP swapping out
fallback counting".

Link: https://lkml.kernel.org/r/20220113023839.758845-1-yang.yang29@zte.com.cn
Signed-off-by: Yang Yang <yang.yang29@zte.com.cn>
Reviewed-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Cc: Hugh Dickins <hughd@google.com>
Cc: Yang Shi <yang.shi@linux.alibaba.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Saravanan D <saravanand@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Yang Yang 2022-03-22 14:46:33 -07:00 committed by Linus Torvalds
parent d8c47cc7bf
commit 4d45c3aff5
3 changed files with 9 additions and 0 deletions
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3
include/linux/vm_event_item.h
View File

@ -129,6 +129,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
#ifdef CONFIG_SWAP
SWAP_RA,
SWAP_RA_HIT,
#ifdef CONFIG_KSM
KSM_SWPIN_COPY,
#endif
#endif
#ifdef CONFIG_X86
DIRECT_MAP_LEVEL2_SPLIT,

3
mm/ksm.c
View File

@ -2595,6 +2595,9 @@ struct page *ksm_might_need_to_copy(struct page *page,
SetPageDirty(new_page);
__SetPageUptodate(new_page);
__SetPageLocked(new_page);
#ifdef CONFIG_SWAP
count_vm_event(KSM_SWPIN_COPY);
#endif
}
return new_page;

3
mm/vmstat.c
View File

@ -1388,6 +1388,9 @@ const char * const vmstat_text[] = {
#ifdef CONFIG_SWAP
"swap_ra",
"swap_ra_hit",
#ifdef CONFIG_KSM
"ksm_swpin_copy",
#endif
#endif
#ifdef CONFIG_X86
"direct_map_level2_splits",