From: Ben Hutchings <bhutchings@solarflare.com>
To: Ivan Novick <novickivan@gmail.com>
Cc: netdev@vger.kernel.org, jmatthews@greenplum.com,
Tim Heath <theath@greenplum.com>,
Herbert Xu <herbert@gondor.apana.org.au>
Subject: Re: TCP not triggering a fast retransmit?
Date: Thu, 01 Jul 2010 02:23:53 +0100 [thread overview]
Message-ID: <1277947433.4878.11.camel@localhost> (raw)
In-Reply-To: <AANLkTimL7_h4J46-WyUYfXYX87t6tQzIn1YRrvJletWB@mail.gmail.com>
On Wed, 2010-06-30 at 17:27 -0700, Ivan Novick wrote:
> On Wed, Jun 30, 2010 at 2:03 PM, Ben Hutchings
> <bhutchings@solarflare.com> wrote:
> > On Wed, 2010-06-30 at 11:04 -0700, Ivan Novick wrote:
> >> Hello all,
> >>
> >> Attached is a packet capture from my application that is running on
> >> RedHat Enterprise Linux 5.4
> >>
> >> I am seeing a Retransmission timeout but I was hoping this case would
> >> go into fast retransmit and not RTO.
> >>
> >> I am wondering why did the sender not send more data? If the sender
> >> was to send more data and extend the window then it would seem the
> >> duplicate acks or SACKS should trigger fast retransmit.
> > [...]
> >
> > In that packet capture I see TCP payload lengths which are 2, 3 and 4
> > times the usual MSS of 1448 bytes, which implies that GRO or LRO is in
> > use. In RHEL 5.4 the TCP stack does not ACK often enough in this case
> > because it is missing this change:
> >
> > commit ff9b5e0f08cb650d113eef0c654f931c0a7ae730
> > Author: Herbert Xu <herbert@gondor.apana.org.au>
> > Date: Thu Aug 31 15:11:02 2006 -0700
> >
> > [TCP]: Fix rcv mss estimate for LRO
>
> Wow, Thanks! Is this the patch you are talking about:
> http://www.mail-archive.com/netdev@vger.kernel.org/msg21151.html ?
>
> It looks like a one liner. I could apply it and rebuild my RHEL 5.4
> to see if it helps.
Right, that's the same patch.
Ben.
--
Ben Hutchings, Senior Software Engineer, Solarflare Communications
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.
prev parent reply other threads:[~2010-07-01 1:23 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-06-30 18:04 TCP not triggering a fast retransmit? Ivan Novick
2010-06-30 19:26 ` Brian Bloniarz
2010-06-30 20:06 ` Mitchell Erblich
2010-06-30 20:14 ` Ivan Novick
2010-06-30 20:43 ` Mitchell Erblich
2010-06-30 21:03 ` Ben Hutchings
2010-06-30 21:22 ` David Miller
2010-06-30 23:10 ` Mitchell Erblich
2010-07-01 0:27 ` Ivan Novick
2010-07-01 1:23 ` Ben Hutchings [this message]
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