Re: 2.6.1[78] page allocation failure. order:3, mode:0x20

[Holger Kiehl <Holger.Kiehl@dwd.de>]

On Fri, 22 Sep 2006, Andrew Morton wrote:

> On Fri, 22 Sep 2006 07:27:18 +0000 (GMT)
> Holger Kiehl <Holger.Kiehl@dwd.de> wrote:
>
> > I get some of the "page allocation failure" errors. My hardware is 4 CPU
> > Opteron with one quad + one dual intel e1000 cards. Kernel is plain 2.6.18
> > and for two cards MTU is set to 9000.
> >
> >     Sep 21 21:03:15 athena kernel: vsftpd: page allocation failure. order:3, mode:0x20
> >     Sep 21 21:03:15 athena kernel:
> >     Sep 21 21:03:15 athena kernel: Call Trace:
> >     Sep 21 21:03:15 athena kernel:  <IRQ> [<ffffffff8024e516>] __alloc_pages+0x282/0x29b
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff8807aa93>] :ip_tables:ipt_do_table+0x1eb/0x318
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff8026614b>] cache_grow+0x134/0x33d
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff8026664c>] cache_alloc_refill+0x189/0x1d7
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff80266724>] __kmalloc+0x8a/0x94
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff803b5438>] __alloc_skb+0x5c/0x123
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff803b5f2e>] __netdev_alloc_skb+0x12/0x2d
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff8033cb22>] e1000_alloc_rx_buffers+0x6f/0x2f3
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff803d1234>] ip_local_deliver+0x173/0x23b
> >     Sep 21 21:03:15 athena kernel:  [<ffffffff8033d29a>] e1000_clean_rx_irq+0x4f4/0x514
>
> Is OK, it's just a warning and it is expected - the kernel will recover.
>
> I'm half-inclined to shut the warning up by sticking a __GFP_NOWARN in there.
>
> But on the other hand, that warning is handy sometimes.  How come kmalloc
> decided to request a 32k hunk of memory when the MTU size is only 9k?  Is
> the driver doing something dumb?
>
> 	else if (max_frame <= E1000_RXBUFFER_8192)
> 		adapter->rx_buffer_len = E1000_RXBUFFER_8192;
> 	else if (max_frame <= E1000_RXBUFFER_16384)
> 		adapter->rx_buffer_len = E1000_RXBUFFER_16384;
>
> It sure is.
>
> This is going to cause an 9000-byte MTU to use a 16384-byte allocation.
> e1000_alloc_rx_buffers() adds two bytes to that, so we do kmalloc(16386),
> which causes the slab allocator to request 32768 bytes.  All for a 9kbyte skb.
I searched the list, which I should have done before asking (I was not sure
if this was due to the e1000) and found this

   http://www.ussg.iu.edu/hypermail/linux/kernel/0608.0/0942.html

discusion from 3rd August. As a summary I read that people are trying to find
a solution, in the meantime one should set /proc/sys/vm/min_free_kbytes to
65000 or higher, to ensure that the driver gets enough unfragmented memory.

Holger

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