linux-kernel - Re: Cache not being reclaimed?

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Date:	Wed, 5 Sep 2007 05:45:01 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	pomac@...or.com
Cc:	Linux-kernel@...r.kernel.org
Subject: Re: Cache not being reclaimed?

> On Wed, 05 Sep 2007 03:28:07 +0200 Ian Kumlien <pomac@...or.com> wrote:
> Hi, 
> 
> I have just had a quite unexpected 'low memory situation'...
> 
> This is a AMD64 machine with 2 gig memory, running 64 bit userland.
> 
> Kernel: 2.6.23-rc3-git10, updating to -rc5-* as soon as i can.
> I'm using SLUB:s
> 
> 
> To me, this looks odd... I thought that any cached memory would be
> reclamed but it was always full.
> 
> Ideas?
> 
> One example from dmesg:
> swapper: page allocation failure. order:1, mode:0x4020
> 
> Call Trace:
>  <IRQ>  [<ffffffff8026c7ef>] __alloc_pages+0x30f/0x330
>  [<ffffffff8028a0a1>] __slab_alloc+0x141/0x590
>  [<ffffffff805a5937>] __netdev_alloc_skb+0x17/0x40
>  [<ffffffff805a5937>] __netdev_alloc_skb+0x17/0x40
>  [<ffffffff8028b470>] __kmalloc_track_caller+0xa0/0xc0
>  [<ffffffff805a4b3f>] __alloc_skb+0x6f/0x150
>  [<ffffffff805a5937>] __netdev_alloc_skb+0x17/0x40
>  [<ffffffff88010945>] :sky2:sky2_rx_alloc+0x25/0xf0
>  [<ffffffff88013b0c>] :sky2:sky2_poll+0x6dc/0xcf0
>  [<ffffffff805e5f60>] tcp_delack_timer+0x0/0x210
>  [<ffffffff805ac38a>] net_rx_action+0x8a/0x140
>  [<ffffffff80242ac9>] __do_softirq+0x69/0xe0
>  [<ffffffff8020cd9c>] call_softirq+0x1c/0x30
>  [<ffffffff8020eb75>] do_softirq+0x35/0x90
>  [<ffffffff8020ede0>] do_IRQ+0x80/0x100
>  [<ffffffff8020ad00>] default_idle+0x0/0x40
>  [<ffffffff8020c121>] ret_from_intr+0x0/0xa
>  <EOI>  [<ffffffff8020ad29>] default_idle+0x29/0x40
>  [<ffffffff8020ade1>] cpu_idle+0xa1/0xf0
> 

An order-1 GFP_ATOMIC allocation can fail, and networking should recover
from it.

If this is happening a lot then someting might have been broken.  Do you
have reason to believe that the frequency of this happening has inreased?
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