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From: "Michael Chan" <mchan@broadcom.com>
To: "CaT" <cat@zip.com.au>, jd@disjunkt.com
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, "netdev" <netdev@vger.kernel.org>
Subject: Re: intermittant petabyte usage reported with broadcom nic
Date: Mon, 21 May 2007 18:15:04 -0700	[thread overview]
Message-ID: <1179796504.1661.152.camel@dell> (raw)
In-Reply-To: <1176596401.5847.7.camel@dell>

On Mon, 2 Apr 2007 11:43:19 +1000 CaT <cat@zip.com.au> wrote:
>  
> I take minute by minute snapshots of network traffic by sampling
> /proc/net/dev and most of the time everything works fine. Occasionally
> though I get petabyte byte traffic and corresponding packet traffic.

We were able to reproduce the problem and confirmed that it was a DMA
problem of the statistics block.  About once an hour on average, wrong
counter values will be DMA'ed to host memory.  Luckily, the DMA write
stays within the intended address range so it will not corrupt other
parts of memory.  Other types of DMA including traffic and buffer
descriptors are not affected.

If you happen to be reading /proc/net/dev within a second after the DMA
corruption, you'll see bogus counters.  One second later and until the
next bad DMA, the counters will be normal again.

We are considering ways to workaround the problem.  Thanks.


  parent reply	other threads:[~2007-05-22  0:26 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-04-02  1:43 intermittant petabyte usage reported with broadcom nic CaT
2007-04-02  7:13 ` Andrew Morton
2007-04-02  7:41   ` CaT
2007-04-02 10:31     ` Jean-Daniel Pauget
2007-04-15  0:20     ` Michael Chan
2007-04-16 19:10       ` Michael Chan
2007-04-16 23:43         ` CaT
2007-04-17 12:01           ` Jean-Daniel Pauget
2007-04-17 15:58           ` Roland Dreier
2007-05-22  1:15       ` Michael Chan [this message]
2007-04-12 22:52   ` CaT
2007-04-12 23:13     ` Andrew Morton
2007-04-12 23:18       ` Roland Dreier
2007-04-12 23:25         ` CaT
2007-04-12 23:15     ` Roland Dreier
2007-04-12 23:28     ` Roland Dreier
2007-04-13  1:15       ` Andi Kleen

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