linux-kernel - Re: Page allocation failures in guest

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Message-ID: <20090811083233.3b2be444@mjolnir.ossman.eu>
Date:	Tue, 11 Aug 2009 08:32:33 +0200
From:	Pierre Ossman <drzeus-list@...eus.cx>
To:	Minchan Kim <minchan.kim@...il.com>
Cc:	avi@...hat.com, kvm@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Wu Fengguang <fengguang.wu@...el.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Rik van Riel <riel@...hat.com>
Subject: Re: Page allocation failures in guest

On Mon, 13 Jul 2009 23:59:52 +0900
Minchan Kim <minchan.kim@...il.com> wrote:

> On Mon, Jul 13, 2009 at 6:51 PM, Pierre Ossman<drzeus-list@...eus.cx> wrote:
> > Jul 12 23:04:54 loki kernel: Active_anon:14065 active_file:87384 inactive_anon:37480
> > Jul 12 23:04:54 loki kernel: inactive_file:95821 unevictable:4 dirty:8 writeback:0 unstable:0
> > Jul 12 23:04:54 loki kernel: free:1344 slab:7113 mapped:4283 pagetables:5656 bounce:0
> > Jul 12 23:04:54 loki kernel: Node 0 DMA free:3988kB min:24kB low:28kB high:36kB active_anon:0kB inactive_anon:0kB active_file:3532kB inactive_file:1032kB unevictable:0kB present:6840kB pages_scanned:0 all_un
> 
> I don't know why present is bigger than free + [in]active anon ?
> Who know this ?
> 
> There are 258 pages in inactive file.
> Unfortunately, it seems we don't have any discardable pages.
> The reclaimer can't sync dirty pages to reclaim them, too.
> That's because we are going on GFP_ATOMIC as I mentioned.
> 

Any ideas here? Is the virtio net driver very GFP_ATOMIC happy so it
drains all those pages? And why is this triggered by a kernel upgrade
in the host?

Avi?

> > reclaimable? no
> > Jul 12 23:04:54 loki kernel: lowmem_reserve[]: 0 994 994 994
> > Jul 12 23:04:54 loki kernel: Node 0 DMA32 free:1388kB min:4020kB low:5024kB high:6028kB active_anon:56260kB inactive_anon:149920kB active_file:346004kB inactive_file:382252kB unevictable:16kB present:1018016
> 
> 
> free : 1388KB min : 4020KB. In addtion, now GFP_HIGH. so calculation
> is as follow for zone_watermark_ok.
> 
> 1388 < (4020 / 2)
> 
> So failed it in zone_watermark_ok.
> AFAIU, it's fairy OOM problem.
> 

I doesn't get out of it though, or at least the virtio net driver
wedges itself.

Rgds
-- 
     -- Pierre Ossman

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