From 4d45c3aff5ebf80d329eba0f90544d20224f612d Mon Sep 17 00:00:00 2001
From: Yang Yang <yang.yang29@zte.com.cn>
Date: Tue, 22 Mar 2022 14:46:33 -0700
Subject: [PATCH] mm/vmstat: add event for ksm swapping in copy
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>
---
include/linux/vm_event_item.h | 3 +++
mm/ksm.c | 3 +++
mm/vmstat.c | 3 +++
3 files changed, 9 insertions(+)
diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
index 7b2363388bfa2..16a0a4fd000be 100644
--- a/include/linux/vm_event_item.h
+++ b/include/linux/vm_event_item.h
@@ -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,
diff --git a/mm/ksm.c b/mm/ksm.c
index c20bd4d9a0d9e..4a7f8614e57d3 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -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;
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 846b670dd346a..d5cc8d739fac1 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -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",
--
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