Re: kswapd craziness in 3.7

From: Rik van Riel
Date: Thu Dec 06 2012 - 15:34:01 EST

On 12/06/2012 03:23 PM, Johannes Weiner wrote:

From: Johannes Weiner <hannes@xxxxxxxxxxx>
Subject: [patch] mm: vmscan: fix inappropriate zone congestion clearing

c702418 ("mm: vmscan: do not keep kswapd looping forever due to
individual uncompactable zones") removed zone watermark checks from
the compaction code in kswapd but left in the zone congestion
clearing, which now happens unconditionally on higher order reclaim.

This messes up the reclaim throttling logic for zones with
dirty/writeback pages, where zones should only lose their congestion
status when their watermarks have been restored.

Remove the clearing from the zone compaction section entirely. The
preliminary zone check and the reclaim loop in kswapd will clear it if
the zone is considered balanced.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>

Reviewed-by: Rik van Riel <riel@xxxxxxxxxx>

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