diff mbox series

[158/227] mm/vmstat: add event for ksm swapping in copy

Message ID 20220322214633.AAEE2C340F4@smtp.kernel.org (mailing list archive)
State New
Headers show
Series [001/227] linux/kthread.h: remove unused macros | expand

Commit Message

Andrew Morton March 22, 2022, 9:46 p.m. UTC 
From: Yang Yang <yang.yang29@zte.com.cn>
Subject: 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>
---

 include/linux/vm_event_item.h |    3 +++
 mm/ksm.c                      |    3 +++
 mm/vmstat.c                   |    3 +++
 3 files changed, 9 insertions(+)
diff mbox series

Patch

--- a/include/linux/vm_event_item.h~mm-vmstat-add-event-for-ksm-swapping-in-copy
+++ a/include/linux/vm_event_item.h
@@ -129,6 +129,9 @@  enum vm_event_item { PGPGIN, PGPGOUT, PS
 #ifdef CONFIG_SWAP
 		SWAP_RA,
 		SWAP_RA_HIT,
+#ifdef CONFIG_KSM
+		KSM_SWPIN_COPY,
+#endif
 #endif
 #ifdef CONFIG_X86
 		DIRECT_MAP_LEVEL2_SPLIT,
--- a/mm/ksm.c~mm-vmstat-add-event-for-ksm-swapping-in-copy
+++ a/mm/ksm.c
@@ -2595,6 +2595,9 @@  struct page *ksm_might_need_to_copy(stru
 		SetPageDirty(new_page);
 		__SetPageUptodate(new_page);
 		__SetPageLocked(new_page);
+#ifdef CONFIG_SWAP
+		count_vm_event(KSM_SWPIN_COPY);
+#endif
 	}
 
 	return new_page;
--- a/mm/vmstat.c~mm-vmstat-add-event-for-ksm-swapping-in-copy
+++ a/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",