linux-kernel - Re: [PATCH] mm,vmscan: only loop back if compaction would fail in all zones

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Date:	Tue, 27 Nov 2012 17:35:56 -0500
From:	Valdis.Kletnieks@...edu
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Rik van Riel <riel@...hat.com>,
	Johannes Hirte <johannes.hirte@....tu-ilmenau.de>,
	akpm@...ux-foundation.org, mgorman@...e.de, jirislaby@...il.com,
	jslaby@...e.cz, zkabelac@...hat.com, mm-commits@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org
Subject: Re: [PATCH] mm,vmscan: only loop back if compaction would fail in all zones

On Sun, 25 Nov 2012 23:10:41 -0500, Johannes Weiner said:

> From: Johannes Weiner <hannes@...xchg.org>
> Subject: [patch] mm: vmscan: fix endless loop in kswapd balancing
>
> Kswapd does not in all places have the same criteria for when it
> considers a zone balanced.  This leads to zones being not reclaimed
> because they are considered just fine and the compaction checks to
> loop over the zonelist again because they are considered unbalanced,
> causing kswapd to run forever.
>
> Add a function, zone_balanced(), that checks the watermark and if
> compaction has enough free memory to do its job.  Then use it
> uniformly for when kswapd needs to check if a zone is balanced.
>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> ---
>  mm/vmscan.c | 27 ++++++++++++++++++---------
>  1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 48550c6..3b0aef4 100644

> +	if (COMPACTION_BUILD && order && !compaction_suitable(zone, order))
> +		return false;

Applying to next-20121117,I had to hand-patch for this other apkm patch:

./Next/merge.log:Applying: mm: use IS_ENABLED(CONFIG_COMPACTION) instead of COMPACTION_BUILD

Probably won't be till tomorrow before I know if this worked, it seems
to take a while before the kswapd storms start hitting (appears to be
a function of uptime - see almost none for 8-16 hours, after 24-30 hours
I'll be having a spinning kswapd most of the time).

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