Re: [PATCH] mm: page_alloc: update the COMPACT[STALL|FAIL] events properly
From: David Rientjes <rientjes@google.com>
Date: 2021-02-01 21:25:35
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On Mon, 1 Feb 2021, Charan Teja Reddy wrote:
By defination, COMPACT[STALL|FAIL] events needs to be counted when there
s/defination/definition/
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is 'At least in one zone compaction wasn't deferred or skipped from the direct compaction'. And when compaction is skipped or deferred, COMPACT_SKIPPED will be returned but it will still go and update these compaction events which is wrong in the sense that COMPACT[STALL|FAIL] is counted without even trying the compaction. Correct this by skipping the counting of these events when COMPACT_SKIPPED is returned for compaction. This indirectly also avoid the unnecessary try into the get_page_from_freelist() when compaction is not even tried. Signed-off-by: Charan Teja Reddy <redacted> --- mm/page_alloc.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 519a60d..531f244 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c@@ -4152,6 +4152,8 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order, memalloc_noreclaim_restore(noreclaim_flag); psi_memstall_leave(&pflags); + if (*compact_result == COMPACT_SKIPPED) + return NULL; /* * At least in one zone compaction wasn't deferred or skipped, so let's * count a compaction stall
This makes sense, I wonder if it would also be useful to check that page == NULL, either in try_to_compact_pages() or here for COMPACT_SKIPPED?