linux-kernel - Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

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Date:	Mon, 22 Jul 2013 18:48:52 +0200
From:	Zlatko Calusic <zcalusic@...sync.net>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	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: Re: [patch 0/3] mm: improve page aging fairness between zones/nodes

On 19.07.2013 22:55, Johannes Weiner wrote:
> The way the page allocator interacts with kswapd creates aging
> imbalances, where the amount of time a userspace page gets in memory
> under reclaim pressure is dependent on which zone, which node the
> allocator took the page frame from.
>
> #1 fixes missed kswapd wakeups on NUMA systems, which lead to some
>     nodes falling behind for a full reclaim cycle relative to the other
>     nodes in the system
>
> #3 fixes an interaction where kswapd and a continuous stream of page
>     allocations keep the preferred zone of a task between the high and
>     low watermark (allocations succeed + kswapd does not go to sleep)
>     indefinitely, completely underutilizing the lower zones and
>     thrashing on the preferred zone
>
> These patches are the aging fairness part of the thrash-detection
> based file LRU balancing.  Andrea recommended to submit them
> separately as they are bugfixes in their own right.
>

I have the patch applied and under testing. So far, so good. It looks 
like it could finally fix the bug that I was chasing few months ago 
(nicely described in your bullet #3). But, few more days of testing will 
be needed before I can reach a quality verdict.

Good job!
-- 
Zlatko

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