linux-kernel - Re: kswapd craziness in 3.7

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Message-ID: <20121128164217.GV8218@suse.de>
Date:	Wed, 28 Nov 2012 16:42:18 +0000
From:	Mel Gorman <mgorman@...e.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	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 Wed, Nov 28, 2012 at 10:13:59AM +0000, Mel Gorman wrote:
> On Tue, Nov 27, 2012 at 03:19:38PM -0800, Linus Torvalds wrote:
> > On Tue, Nov 27, 2012 at 2:26 PM, Johannes Weiner <hannes@...xchg.org> wrote:
> > > On Tue, Nov 27, 2012 at 05:02:36PM -0500, Rik van Riel wrote:
> > >>
> > >> Kswapd going crazy is certainly a large part of the problem.
> > >>
> > >> However, that leaves the issue of page_alloc.c waking up
> > >> kswapd when the system is not actually low on memory.
> > >>
> > >> Instead, kswapd is woken up because memory compaction failed,
> > >> potentially even due to lock contention during compaction!
> > >>
> > >> Ideally the allocation code would only wake up kswapd if
> > >> memory needs to be freed, or in order for kswapd to do
> > >> memory compaction (so the allocator does not have to).
> > >
> > > Maybe I missed something, but shouldn't this be solved with my patch?
> > 
> > Ok, guys. Cage fight!
> > 
> > The rules are simple: two men enter, one man leaves.
> > 
> 
> I'm fairly scorch damaged from this whole cycle already. I won't need a
> prop master to look the part for a thunderdome match.
> 
> > And the one who comes out gets to explain to me which patch(es) I
> > should apply, and which I should revert, if any.
> > 
> 
> Based on the reports I've seen I expect the following to work for 3.7
> 
> Keep
>   96710098 mm: revert "mm: vmscan: scale number of pages reclaimed by reclaim/compaction based on failures"
>   ef6c5be6 fix incorrect NR_FREE_PAGES accounting (appears like memory leak)
> 
> Revert
>   82b212f4 Revert "mm: remove __GFP_NO_KSWAPD"
> 
> Merge
>   mm: vmscan: fix kswapd endless loop on higher order allocation
>   mm: Avoid waking kswapd for THP allocations when compaction is deferred or contended
> 

and
    mm: compaction: Fix return value of capture_free_page

but this one may already be in flight from Andrew's tree as he picked it
up already.

-- 
Mel Gorman
SUSE Labs
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