The patch titled
Subject: mm: compaction: update the COMPACT[STALL|FAIL] events properly
has been added to the -mm tree. Its filename is
mm-compaction-update-the-compact-events-properly.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-compaction-update-the-compact-events-properly.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-compaction-update-the-compact-events-properly.patch
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------------------------------------------------------
From: Charan Teja Reddy <charante@xxxxxxxxxxxxxx>
Subject: mm: compaction: update the COMPACT[STALL|FAIL] events properly
By definition, COMPACT[STALL|FAIL] events needs to be counted when there
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.
There is a corner case where compaction is skipped but still count
COMPACTSTALL event, which is that IRQ came and freed the page and the same
is captured in capture_control.
Link: https://lkml.kernel.org/r/1613151184-21213-1-git-send-email-charante@xxxxxxxxxxxxxx
Signed-off-by: Charan Teja Reddy <charante@xxxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/compaction.c | 8 ++++++++
mm/page_alloc.c | 2 ++
2 files changed, 10 insertions(+)
--- a/mm/compaction.c~mm-compaction-update-the-compact-events-properly
+++ a/mm/compaction.c
@@ -2494,6 +2494,14 @@ static enum compact_result compact_zone_
*/
WRITE_ONCE(current->capture_control, NULL);
*capture = READ_ONCE(capc.page);
+ /*
+ * Technically, it is also possible that compaction is skipped but
+ * the page is still captured out of luck(IRQ came and freed the page).
+ * Returning COMPACT_SUCCESS in such cases helps in properly accounting
+ * the COMPACT[STALL|FAIL] when compaction is skipped.
+ */
+ if (*capture)
+ ret = COMPACT_SUCCESS;
return ret;
}
--- a/mm/page_alloc.c~mm-compaction-update-the-compact-events-properly
+++ a/mm/page_alloc.c
@@ -4181,6 +4181,8 @@ __alloc_pages_direct_compact(gfp_t gfp_m
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
_
Patches currently in -mm which might be from charante@xxxxxxxxxxxxxx are
mm-compaction-update-the-compact-events-properly.patch
