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mm/page_alloc: fix deferred compaction accounting

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COMPACT_DEFERRED means compaction did not start because past failures
caused the zone to be deferred.  try_to_compact_pages() returns the
maximum result seen while walking the zonelist, so a final
COMPACT_DEFERRED result means no later zone reported that compaction
actually ran.

__alloc_pages_direct_compact() skips COMPACTSTALL and COMPACTFAIL
accounting when try_to_compact_pages() returns COMPACT_SKIPPED, but not
when it returns COMPACT_DEFERRED.  A deferred-only direct compaction
attempt can therefore look like a stall, and then a failure if the
allocation still cannot be satisfied.

Treat COMPACT_DEFERRED like COMPACT_SKIPPED in this accounting path.  If a
later zone runs compaction and returns a result above COMPACT_DEFERRED, or
compact_zone_order() reports COMPACT_SUCCESS for a captured page, the
final result is not COMPACT_DEFERRED and the existing accounting still
runs.

Link: https://lore.kernel.org/tencent_368AF1F3821E46232637BE16D65C45CF3308@qq.com
Fixes: 06dac2f467 ("mm: compaction: update the COMPACT[STALL|FAIL] events properly")
Signed-off-by: fujunjie <fujunjie1@qq.com>
Reviewed-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Brendan Jackman <jackmanb@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
fujunjie 2026-05-26 09:12:48 +00:00 committed by Andrew Morton
parent 8732e14b71
commit 3d4f1a5416
1 changed files with 2 additions and 1 deletions
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3
mm/page_alloc.c
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@ -4161,7 +4161,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
psi_memstall_leave(&pflags);
delayacct_compact_end();
if (*compact_result == COMPACT_SKIPPED)
if (*compact_result == COMPACT_SKIPPED ||
*compact_result == COMPACT_DEFERRED)
return NULL;
/*
* At least in one zone compaction wasn't deferred or skipped, so let's