diff mbox

[Xenial,10/11] mm, oom: protect !costly allocations some more for !CONFIG_COMPACTION

Message ID 20170124162839.6355-11-cascardo@canonical.com
State New
Headers show

Commit Message

Thadeu Lima de Souza Cascardo Jan. 24, 2017, 4:28 p.m. UTC 
From: Michal Hocko <mhocko@suse.com>

BugLink: https://bugs.launchpad.net/bugs/1655842

Joonsoo has reported that he is able to trigger OOM for !costly high
order requests (heavy fork() workload close the OOM) with the new oom
detection rework.  This is because we rely only on should_reclaim_retry
when the compaction is disabled and it only checks watermarks for the
requested order and so we might trigger OOM when there is a lot of free
memory.

It is not very clear what are the usual workloads when the compaction is
disabled.  Relying on high order allocations heavily without any
mechanism to create those orders except for unbound amount of reclaim is
certainly not a good idea.

To prevent from potential regressions let's help this configuration
some.  We have to sacrifice the determinsm though because there simply
is none here possible.  should_compact_retry implementation for
!CONFIG_COMPACTION, which was empty so far, will do watermark check for
order-0 on all eligible zones.  This will cause retrying until either
the reclaim cannot make any further progress or all the zones are
depleted even for order-0 pages.  This means that the number of retries
is basically unbounded for !costly orders but that was the case before
the rework as well so this shouldn't regress.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/1463051677-29418-3-git-send-email-mhocko@kernel.org
Reported-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(backported from commit 31e49bfda18464b9b0cfe42044d5a4be4a0ca0f3)
[cascardo: fixup ac_classzone_idx to ac->classzone_idx]
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
---
 mm/page_alloc.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)
diff mbox

Patch

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index acfda2a..50eba2f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2908,6 +2908,24 @@  should_compact_retry(struct alloc_context *ac, unsigned int order, int alloc_fla
 		     enum migrate_mode *migrate_mode,
 		     int compaction_retries)
 {
+	struct zone *zone;
+	struct zoneref *z;
+
+	if (!order || order > PAGE_ALLOC_COSTLY_ORDER)
+		return false;
+
+	/*
+	 * There are setups with compaction disabled which would prefer to loop
+	 * inside the allocator rather than hit the oom killer prematurely.
+	 * Let's give them a good hope and keep retrying while the order-0
+	 * watermarks are OK.
+	 */
+	for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx,
+					ac->nodemask) {
+		if (zone_watermark_ok(zone, 0, min_wmark_pages(zone),
+					ac->classzone_idx, alloc_flags))
+			return true;
+	}
 	return false;
 }
 #endif /* CONFIG_COMPACTION */