Date: Mon, 27 Oct 2008 17:22:16 +1100
From: Dave Chinner <david@fromorbit.com>
To: Claudio Martins <ctpm@ist.utl.pt>
Cc: linux-kernel@vger.kernel.org
Subject: Re: Order 0 page allocation failure under heavy I/O load
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	linux-kernel@vger.kernel.org
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On Mon, Oct 27, 2008 at 06:47:31AM +0100, Claudio Martins wrote:
> On Sunday 26 October 2008, Dave Chinner wrote:
> 
> > The host will hang for tens of seconds at a time with both CPU cores
> > pegged at 100%, and eventually I get this in dmesg:
> >
> > [1304740.261506] linux: page allocation failure. order:0, mode:0x10000
> > [1304740.261516] Pid: 10705, comm: linux Tainted: P          2.6.26-1-amd64
> 
>  Hello,
> 
>  Have you tried to increase vm.min_free_kbytes to something higher, that is 
> >=30000?

No, because I've found the XFS bug the workload was triggering so
I don't need to run it anymore.

I reported the problem because it appears that we've reported an
allocation failure without very much reclaim scanning (64 pages in
DMA zone, 0 pages in DMA32 zone), and there is apparently pages
available for allocation in the DMA zone:

1304740.262136] Node 0 DMA: 160*4kB 82*8kB 32*16kB 11*32kB 8*64kB 4*128kB 3*256kB 0*512kB 0*1024kB 0*2048kB 1*4096kB = 8048kB

So it appears that memory reclaim has not found the free pages it
apparently has available....

Fundamentally, I/O from a single CPU to a single disk on a machine
with 2GB RAM should not be able to cause allocation failures at all,
especially when the I/O is pure data I/O to a single file. Something
in the default config is busted if I can do that, and that's why
I reported the bug.

Cheers,

Dave.
-- 
Dave Chinner
david@fromorbit.com
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