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BACKPORT: FROMGIT: Multi-gen LRU: fix workingset accounting

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On Android app cycle workloads, MGLRU showed a significant reduction in
workingset refaults although pgpgin/pswpin remained relatively unchanged.
This indicated MGLRU may be undercounting workingset refaults.

This has impact on userspace programs, like Android's LMKD, that monitor
workingset refault statistics to detect thrashing.

It was found that refaults were only accounted if the MGLRU shadow entry
was for a recently evicted folio.  However, recently evicted folios should
be accounted as workingset activation, and refaults should be accounted
regardless of recency.

Fix MGLRU's workingset refault and activation accounting to more closely
match that of the conventional active/inactive LRU.

Link: https://lkml.kernel.org/r/20230523205922.3852731-1-kaleshsingh@google.com
Fixes: ac35a49023 ("mm: multi-gen LRU: minimal implementation")
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Reported-by: Charan Teja Kalla <quic_charante@quicinc.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: Jan Alexander Steffens (heftig) <heftig@archlinux.org>
Cc: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
(cherry picked from commit 02ad728453d2ddb09d7ce5e59854ebb27544d488 https://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm.git mm-unstable)
Bug: 284043217
[ Kalesh Singh - Fix conflicts in mm/workingset.c ]
Signed-off-by: Kalesh Singh <kaleshsingh@google.com>
Change-Id: I6d42cca9064e66099fbbc20aa2143961f84b2003
This commit is contained in:
Kalesh Singh 2023-05-23 13:59:21 -07:00
parent 80d7019423
commit 500484f5be
2 changed files with 3 additions and 2 deletions
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1
mm/vmscan.c
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@ -4859,7 +4859,6 @@ static bool sort_folio(struct lruvec *lruvec, struct folio *folio, int tier_idx)
WRITE_ONCE(lrugen->protected[hist][type][tier - 1],
lrugen->protected[hist][type][tier - 1] + delta);
__mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
return true;
}

4
mm/workingset.c
View file

@ -272,6 +272,8 @@ static void lru_gen_refault(struct folio *folio, void *shadow)
lruvec = mem_cgroup_lruvec(memcg, pgdat);
lrugen = &lruvec->lrugen;
mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta);
min_seq = READ_ONCE(lrugen->min_seq[type]);
if ((token >> LRU_REFS_WIDTH) != (min_seq & (EVICTION_MASK >> LRU_REFS_WIDTH)))
goto unlock;
@ -282,7 +284,7 @@ static void lru_gen_refault(struct folio *folio, void *shadow)
tier = lru_tier_from_refs(refs);
atomic_long_add(delta, &lrugen->refaulted[hist][type][tier]);
mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta);
mod_lruvec_state(lruvec, WORKINGSET_ACTIVATE_BASE + type, delta);
/*
* Count the following two cases as stalls: