linux-kernel - Re: kswapd craziness in 3.7

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Message-ID: <50B52DC4.5000109@redhat.com>
Date:	Tue, 27 Nov 2012 16:16:52 -0500
From:	Rik van Riel <riel@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	George Spelvin <linux@...izon.com>,
	Johannes Hirte <johannes.hirte@....tu-ilmenau.de>,
	Tomas Racek <tracek@...hat.com>, Jan Kara <jack@...e.cz>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Josh Boyer <jwboyer@...il.com>,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Jiri Slaby <jslaby@...e.cz>,
	Thorsten Leemhuis <fedora@...mhuis.info>,
	Zdenek Kabelac <zkabelac@...hat.com>,
	Bruno Wolff III <bruno@...ff.to>,
	linux-mm <linux-mm@...ck.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: kswapd craziness in 3.7

On 11/27/2012 03:58 PM, Linus Torvalds wrote:
> Note that in the meantime, I've also applied (through Andrew) the
> patch that reverts commit c654345924f7 (see commit 82b212f40059
> 'Revert "mm: remove __GFP_NO_KSWAPD"').
>
> I wonder if that revert may be bogus, and a result of this same issue.
> Maybe that revert should be reverted, and replaced with your patch?
>
> Mel? Zdenek? What's the status here?

Mel posted several patches to fix the kswapd issue.  This one is
slightly more risky than the outright revert, but probably preferred
from a performance point of view:

https://lkml.org/lkml/2012/11/12/151

It works by skipping the kswapd wakeup for THP allocations, only
if compaction is deferred or contended.

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