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authorKalesh Singh <kaleshsingh@google.com>2023-05-23 13:59:21 -0700
committerAndrew Morton <akpm@linux-foundation.org>2023-06-09 16:25:46 -0700
commit3af0191a594d5ca5d6d2e3602b5d4284c6835e77 (patch)
tree53b368f7763895ae8914982efa4ec9796180bc6b /mm/workingset.c
parent06b27ce36a1a3dc5ea6f8314d0c7d1baa9f8ece7 (diff)
Multi-gen LRU: fix workingset accounting
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: ac35a4902374 ("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>
Diffstat (limited to 'mm/workingset.c')
-rw-r--r--mm/workingset.c10
1 files changed, 7 insertions, 3 deletions
diff --git a/mm/workingset.c b/mm/workingset.c
index 5796e927e6d7..4686ae363000 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -278,6 +278,7 @@ static bool lru_gen_test_recent(void *shadow, bool file, struct lruvec **lruvec,
static void lru_gen_refault(struct folio *folio, void *shadow)
{
+ bool recent;
int hist, tier, refs;
bool workingset;
unsigned long token;
@@ -288,10 +289,13 @@ static void lru_gen_refault(struct folio *folio, void *shadow)
rcu_read_lock();
- if (!lru_gen_test_recent(shadow, type, &lruvec, &token, &workingset))
+ recent = lru_gen_test_recent(shadow, type, &lruvec, &token, &workingset);
+ if (lruvec != folio_lruvec(folio))
goto unlock;
- if (lruvec != folio_lruvec(folio))
+ mod_lruvec_state(lruvec, WORKINGSET_REFAULT_BASE + type, delta);
+
+ if (!recent)
goto unlock;
lrugen = &lruvec->lrugen;
@@ -302,7 +306,7 @@ 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: