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

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Message-ID: <20130223061414.GA16883@merlins.org>
Date:	Fri, 22 Feb 2013 22:14:14 -0800
From:	Marc MERLIN <marc@...lins.org>
To:	Johannes Berg <johannes@...solutions.net>
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 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.

Marc
-- 
"A mouse is a device used to point at the xterm you want to type in" - A.S.R.
Microsoft is to operating systems ....
                                      .... what McDonalds is to gourmet cooking
Home page: http://marc.merlins.org/
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