linux-kernel - [patch 1/3] mm: vmscan: fix numa reclaim balance problem in kswapd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Fri, 19 Jul 2013 16:55:23 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Andrea Arcangeli <aarcange@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: [patch 1/3] mm: vmscan: fix numa reclaim balance problem in kswapd

When the page allocator fails to get a page from all zones in its
given zonelist, it wakes up the per-node kswapds for all zones that
are at their low watermark.

However, with a system under load and the free page counters being
per-cpu approximations, the observed counter value in a zone can
fluctuate enough that the allocation fails but the kswapd wakeup is
also skipped while the zone is still really close to the low
watermark.

When one node misses a wakeup like this, it won't be aged before all
the other node's zones are down to their low watermarks again.  And
skipping a full aging cycle is an obvious fairness problem.

Kswapd runs until the high watermarks are restored, so it should also
be woken when the high watermarks are not met.  This ages nodes more
equally and creates a safety margin for the page counter fluctuation.

By using zone_balanced(), it will now check, in addition to the
watermark, if compaction requires more order-0 pages to create a
higher order page.

Signed-off-by: Johannes Weiner <hannes@...xchg.org>
---
 mm/vmscan.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index e364542..bccc6d3 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -3277,7 +3277,7 @@ void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx)
 	}
 	if (!waitqueue_active(&pgdat->kswapd_wait))
 		return;
-	if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0))
+	if (zone_balanced(zone, order, 0, 0))
 		return;

 	trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order);
-- 
1.8.3.2

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/