linux-kernel - Re: [patch 1/2] mm: page_alloc: reset aging cycle with GFP

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Message-ID: <530F9EB2.3070800@redhat.com>
Date:	Thu, 27 Feb 2014 15:23:14 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Johannes Weiner <hannes@...xchg.org>, Mel Gorman <mgorman@...e.de>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Stancek <jstancek@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] mm: page_alloc: reset aging cycle with GFP_THISNODE

On 02/26/2014 03:13 PM, Johannes Weiner wrote:

> Would this be an acceptable replacement for 1/2?

Looks reasonable to me. This should avoid the issues that
were observed with NUMA migrations.

> ---
>
> From: Johannes Weiner <hannes@...xchg.org>
> Subject: [patch 1/2] mm: page_alloc: exempt GFP_THISNODE allocations from zone
>   fairness
>
> Jan Stancek reports manual page migration encountering allocation
> failures after some pages when there is still plenty of memory free,
> and bisected the problem down to 81c0a2bb515f ("mm: page_alloc: fair
> zone allocator policy").
>
> The problem is that GFP_THISNODE obeys the zone fairness allocation
> batches on one hand, but doesn't reset them and wake kswapd on the
> other hand.  After a few of those allocations, the batches are
> exhausted and the allocations fail.
>
> Fixing this means either having GFP_THISNODE wake up kswapd, or
> GFP_THISNODE not participating in zone fairness at all.  The latter
> seems safer as an acute bugfix, we can clean up later.
>
> Reported-by: Jan Stancek <jstancek@...hat.com>
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> Cc: <stable@...nel.org> # 3.12+

Acked-by: Rik van Riel <riel@...hat.com>

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