From: Yang Yang <yang.yang29@xxxxxxxxxx> 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@xxxxxxxxxx Signed-off-by: Yang Yang <yang.yang29@xxxxxxxxxx> Reviewed-by: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx> Cc: Hugh Dickins <hughd@xxxxxxxxxx> Cc: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Saravanan D <saravanand@xxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- include/linux/vm_event_item.h | 3 +++ mm/ksm.c | 3 +++ mm/vmstat.c | 3 +++ 3 files changed, 9 insertions(+) --- 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", _
