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authorYu Zhao <yuzhao@google.com>2021-02-24 12:03:08 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2021-02-24 13:38:29 -0800
commitcad8320b4b395702e49578580c70026c8271ea88 (patch)
treeee7953bb03f37d9e62043f9db2c31870060ab5e3 /mm/swap_state.c
parente48333b660d57898ad6240570084ffa734f64368 (diff)
downloadlinux-cad8320b4b395702e49578580c70026c8271ea88.tar.bz2
mm/swap: don't SetPageWorkingset unconditionally during swapin
We are capable of SetPageWorkingset based on refault distances after commit aae466b0052e ("mm/swap: implement workingset detection for anonymous LRU"). This is done by workingset_refault(), which is right above the unconditional SetPageWorkingset deleted by this patch. The unconditional SetPageWorkingset miscategorizes pages that are read ahead or never belonged to the working set (e.g., tmpfs pages accessed only once by fd). When those pages are swapped in (after they were swapped out) for the first time, they skew PSI (when using async swap). When this happens again, depending on their refault distances, they might skew workingset_restore_anon counter in addition to PSI because their shadows indicate they were part of the working set. Historically, SetPageWorkingset was added as part of the PSI series, and Johannes said: "It was meant to mark incoming pages under IO with SetPageWorkingset when waiting for them constituted a memory stall. On the page cache side, because we HAVE workingset detection, this was specific to recently evicted pages that had been active in their previous life. On the anon side, the aging algorithm had no distinction between workingset and sporadically used pages. Given the choice between a) no swapin stalls are pressure and b) all swapin stalls are pressure, I went with the latter in order to detect swap storms. The false positive case - high rate of swapin without severe memory pressure - was relatively unlikely, because we tried to avoid swapping until everything was completely on fire in the first place." Link: https://lkml.kernel.org/r/20201209012400.1771150-1-yuzhao@google.com Link: https://lkml.kernel.org/r/20201214231253.62313-1-yuzhao@google.com Signed-off-by: Yu Zhao <yuzhao@google.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Joonsoo Kim <iamjoonsoo.kim@lge.com> Acked-by: Michal Hocko <mhocko@suse.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/swap_state.c')
-rw-r--r--mm/swap_state.c1
1 files changed, 0 insertions, 1 deletions
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 3507c82b2ef1..807b00eae969 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -537,7 +537,6 @@ struct page *__read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
workingset_refault(page, shadow);
/* Caller will initiate read into locked page */
- SetPageWorkingset(page);
lru_cache_add(page);
*new_page_allocated = true;
return page;