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Date: Thu, 12 Apr 2012 01:56:38 +0200
From: Johannes Weiner <hannes@cmpxchg.org>
Subject: Re: [PATCH V2 5/5] memcg: change the target nr_to_reclaim for each
 memcg under kswapd
Message-ID: <20120411235638.GA1787@cmpxchg.org>
References: <1334181627-26942-1-git-send-email-yinghan@google.com>
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To: Ying Han <yinghan@google.com>
Cc: Michal Hocko <mhocko@suse.cz>, Mel Gorman <mel@csn.ul.ie>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Rik van Riel <riel@redhat.com>, Hillf Danton <dhillf@gmail.com>, Hugh Dickins <hughd@google.com>, Dan Magenheimer <dan.magenheimer@oracle.com>, linux-mm@kvack.org

On Wed, Apr 11, 2012 at 03:00:27PM -0700, Ying Han wrote:
> Under global background reclaim, the sc->nr_to_reclaim is set to
> ULONG_MAX. Now we are iterating all memcgs under the zone and we
> shouldn't pass the pressure from kswapd for each memcg.
> 
> After all, the balance_pgdat() breaks after reclaiming SWAP_CLUSTER_MAX
> pages to prevent building up reclaim priorities.

shrink_mem_cgroup_zone() bails out of a zone, balance_pgdat() bails
out of a priority loop, there is quite a difference.

After this patch, kswapd no longer puts equal pressure on all zones in
the zonelist, which was a key reason why we could justify bailing
early out of individual zones in direct reclaim: kswapd will restore
fairness.

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