Message-ID: <1361390290.8579.4.camel@jlt4.sipsolutions.net> (sfid-20130220_205853_849162_10187BDB)
Subject: Re: 3.7.8/amd64 full interrupt hangs due to iwlwifi under big nfs
 copies out
From: Johannes Berg <johannes@sipsolutions.net>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Marc MERLIN <marc@merlins.org>, David Miller <davem@davemloft.net>,
	Larry.Finger@lwfinger.net, bhutchings@solarflare.com,
	linux-wireless@vger.kernel.org, netdev@vger.kernel.org
Date: Wed, 20 Feb 2013 20:58:10 +0100
In-Reply-To: <1361387854.19353.214.camel@edumazet-glaptop> (sfid-20130220_201740_409859_E87FECD4)
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On Wed, 2013-02-20 at 11:17 -0800, Eric Dumazet wrote:
> On Wed, 2013-02-20 at 19:16 +0100, Johannes Berg wrote:
> 
> > Yes and no. The current code doesn't pull in much data, not even the IP
> > header, so worst case it copies 14 bytes (ethernet header) in mac80211
> > to obtain alignment. By pulling in everything here, it later has to copy
> > everything again later to obtain alignment.
> 
> Can you give me pointers to the code doing that ?

Sure: net/mac80211/rx.c ~line 1900, look for #ifndef
CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS.

> On x86 we should not doing anything.

We don't do anything if CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS is
defined.

johannes