From: Stephen Satchell <list@fluent2.pyramid.net>
To: Shesha@asu.edu, linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org
Subject: Re: Why throughput increases as MTU size is increased
Date: Wed, 30 Apr 2003 08:30:51 -0700 [thread overview]
Message-ID: <5.2.0.9.0.20030430082756.00a73730@fluent2.pyramid.net> (raw)
In-Reply-To: <Pine.GSO.4.21.0304300706400.28571-100000@general2.asu.edu>
At 07:10 AM 4/30/03 -0700, Shesha@asu.edu wrote:
> When I measure the performance of iSCSI on XScale with MTU size = 1500
> bytes,
>a throughput of 32 Mbps was observed. As the MTU size was increased, the
>throughput also increased.
>1500 -> 32 Mbps
>3000 -> 56
>4500 -> 80
>6000 -> 100
>7500 -> 108
>9000 -> 108
The non-linear increase as you change MTU is the dead give-away: the
slow-start algorithm is working just fine. The reason you didn't get
double the throughput as you doubled the MTU is that the slow-start
algorithm ramps based on packet count, so as you increase the MTU the
packet rate slope remains reasonably constant. If you have the source
code, you can turn off slow-start using setsocketopt(), and see what happens.
Have you considered trying a longer file?
--
X -> unknown; Spurt -> drip of water under pressure
Expert -> X-Spurt -> Unknown drip under pressure.
prev parent reply other threads:[~2003-04-30 15:18 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-04-30 14:10 Why throughput increases as MTU size is increased Shesha
2003-04-30 15:30 ` Stephen Satchell [this message]
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