Commit 06dac2f4 authored by Charan Teja Reddy's avatar Charan Teja Reddy Committed by Linus Torvalds
Browse files

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@codeaurora.org


Signed-off-by: default avatarCharan Teja Reddy <charante@codeaurora.org>
Acked-by: default avatarVlastimil Babka <vbabka@suse.cz>
Acked-by: default avatarDavid Rientjes <rientjes@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ef498438

mm/compaction.c

+8 −0
Original line number Diff line number Diff line
@@ -2529,6 +2529,14 @@ static enum compact_result compact_zone_order(struct zone *zone, int order, 
	 */

	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;

}

mm/page_alloc.c

+2 −0
Original line number Diff line number Diff line
@@ -4204,6 +4204,8 @@ __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