linux-kernel - Re: kswapd craziness in 3.7

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Date:	Wed, 28 Nov 2012 14:52:15 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Rik van Riel <riel@...hat.com>,
	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, 28 Nov 2012 10:13:59 +0000
Mel Gorman <mgorman@...e.de> wrote:

> 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

"mm: Avoid waking kswapd for THP ..." is marked "I have not tested it
myself" and when Zdenek tested it he hit an unexplained oom.

> Johannes' patch should remove the necessity for __GFP_NO_KSWAPD revert but I
> think we should also avoid waking kswapd for THP allocations if compaction
> is deferred. Johannes' patch might mean that kswapd goes quickly go back
> to sleep but it's still busy work.
> 
> 3.6 is still known to be screwed in terms of THP because of the amount of
> time it can spend in compaction after lumpy reclaim was removed. This is
> my old list of patches I felt needed to be backported after 3.7 came out.
> They are not tagged -stable, I'll be sending it to Greg manually.
> 
> e64c523 mm: compaction: abort compaction loop if lock is contended or run too long
> 3cc668f mm: compaction: move fatal signal check out of compact_checklock_irqsave
> 661c4cb mm: compaction: Update try_to_compact_pages()kerneldoc comment
> 2a1402a mm: compaction: acquire the zone->lru_lock as late as possible
> f40d1e4 mm: compaction: acquire the zone->lock as late as possible
> 753341a revert "mm: have order > 0 compaction start off where it left"
> bb13ffe mm: compaction: cache if a pageblock was scanned and no pages were isolated
> c89511a mm: compaction: Restart compaction from near where it left off
> 6299702 mm: compaction: clear PG_migrate_skip based on compaction and reclaim activity
> 0db63d7 mm: compaction: correct the nr_strict va isolated check for CMA
> 
> Only Johannes' patch needs to be added to this list. kswapd is not woken
> for THP in 3.6 but as it calls compaction for other high-order allocations
> it still makes sense.

Please identify "Johannes' patch"?
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