linux-kernel - Re: kswapd craziness in 3.7

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Message-ID: <CA+55aFyrNRF8nWyozDPi4O1bdjzO189YAgMukyhTOZ9fwKqOpA@mail.gmail.com>
Date:	Tue, 27 Nov 2012 15:19:38 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Rik van Riel <riel@...hat.com>,
	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 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.

And the one who comes out gets to explain to me which patch(es) I
should apply, and which I should revert, if any.

My current guess is that I should apply the one Johannes just sent
("mm: vmscan: fix kswapd endless loop on higher order allocation")
after having added the cc to stable to it, and then revert the recent
revert (commit 82b212f40059).

But I await the Thunderdome. <Cue Tina Turner "We Don't Need Another Hero">

                      Linus
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