linux-kernel - Re: Page alloc failures under network/disk IO load

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Message-Id: <1228380128.5092.15.camel@twins>
Date:	Thu, 04 Dec 2008 09:42:08 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Dan Noé <dpn@...merica.net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: Page alloc failures under network/disk IO load

On Thu, 2008-12-04 at 09:23 +0100, Peter Zijlstra wrote:
> On Wed, 2008-12-03 at 22:27 -0500, Dan Noé wrote:
> > This is on Linux 2.6.28-rc7, on a Core 2 Duo.  The system has plenty of
> > memory:
> > 
> >              total       used       free     shared    buffers
> > cached
> > Mem:          1893       1822         70          0          0
> 
> filled to the brim with data
> 
> > 1573
> > -/+ buffers/cache:        249       1644
> > Swap:         1906         37       1868
> > 
> > I am using rsync to transfer data onto this system.  The filesystem is
> > XFS, and the target drive is a 1TB Western Digital on ata_piix.  The
> > system files are on a RAID 1 (Linux md, also on ata_piix).
> > 
> > Periodically I get page allocation failures, from __netdev_alloc_skb.
> > I suppose this causes the driver to drop packets and thus hurts
> > performance.
> 
> There isn't much we can do about that, memory is filled and your network
> card tries to allocate memory in a mode that doesn't allow freeing some.
> 
> Looking at the timestamps its not very frequent, so it doesn't hurt
> performance much if anything. If you're really bothered with this, you
> could quiet it by sticking in a __GFP_NOWARN in __netdev_alloc_skb() or
> something..

Another thing you can do is increase /proc/sys/vm/min_free_kbytes
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