netdev - Re: 3.7.8/amd64 full interrupt hangs due to iwlwifi under big nfs copies out

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Date:	Tue, 26 Feb 2013 21:54:59 +0100
From:	Johannes Berg <johannes@...solutions.net>
To:	Marc MERLIN <marc@...lins.org>
Cc:	Eric Dumazet <eric.dumazet@...il.com>,
	David Miller <davem@...emloft.net>, Larry.Finger@...inger.net,
	bhutchings@...arflare.com, linux-wireless@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: 3.7.8/amd64 full interrupt hangs due to iwlwifi under big nfs
 copies out

On Fri, 2013-02-22 at 22:14 -0800, Marc MERLIN wrote:
> On Wed, Feb 20, 2013 at 10:15:03AM +0100, Johannes Berg wrote:
> > On Wed, 2013-02-20 at 10:12 +0100, Johannes Berg wrote:
> > > On Tue, 2013-02-19 at 08:21 -0800, Eric Dumazet wrote:
> > > > On Tue, 2013-02-19 at 11:03 +0100, Johannes Berg wrote:
> > > > > On Mon, 2013-02-18 at 21:17 -0800, Eric Dumazet wrote:
> > > > > 
> > > > > > > chrome: page allocation failure: order:1, mode:0x4020
> > > > > > > Pid: 8730, comm: chrome Tainted: G           O 3.7.8-amd64-preempt-20121226-fixwd #1
> > > > > > > Call Trace:
> > > > > > >  <IRQ>  [<ffffffff810d5f38>] warn_alloc_failed+0x117/0x12c
> > > > > 
> > > > > > You could try to load iwlwifi with amsdu_size_8K set to 0 (disable)
> > > > > > 
> > > > > > It should hopefully use order-0 pages
> > > > > 
> > > > > It will, do that then, unfortunately it can't switch at runtime because
> > > > > it advertised this support to the access point or clients.
> > > > 
> > > > What are the drawbacks of setting amsdu_size_8K to 0 by default ?
> > > 
> > > We're discussing this now, the only downside would be that we couldn't
> > > receive 8k A-MSDUs. Thing is, practically nobody uses A-MSDU anyway, and
> > > even when I suspect the difference between 4k and 8k won't be huge.
> > 
> > OTOH, this affects the protocol, and when you really can't allocate any
> > order-1 pages you pointed out yourself that many other things also won't
> > work, so I'm not really sure it makes a big difference if we change the
> > driver?
> 
> That as an unscientific test, but when I did the NFS eats all my pages
> test using ethernet, my system didn't hang like it did with iwlagn.
> 
> So while the NFS code is definitely doing something wrong when it uses
> its default huge buffers, the e1000e code deals with it without hanging
> my system.
> 
> So thanks for trying to improve the iwlagn code to avoid those system
> lockups.

We'll be submitting a patch to make single pages default.

johannes

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