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Message-ID: <4BB0DBFD.30904@hp.com>
Date: Mon, 29 Mar 2010 09:57:33 -0700
From: Rick Jones <rick.jones2@...com>
To: michal.simek@...alogix.com
CC: LKML <linux-kernel@...r.kernel.org>,
John Williams <john.williams@...alogix.com>,
netdev@...r.kernel.org, Grant Likely <grant.likely@...retlab.ca>,
John Linn <John.Linn@...inx.com>,
"Steven J. Magnani" <steve@...idescorp.com>,
Arnd Bergmann <arnd@...db.de>, akpm@...ux-foundation.org
Subject: Re: Network performance - iperf
Rick Jones wrote:
> I don't know how to set fixed socket buffer sizes in iperf, if you were
> running netperf though I would suggest fixing the socket buffer sizes
> with the test-specific -s (affects local) and -S (affects remote) options:
>
> netperf -t TCP_STREAM -H <remote> -l 30 -- -s 32K -S 32K -m 32K
>
> to test the hypothesis that the autotuning of the socket buffers/window
> size is allowing the windows to grow in the larger memory cases beyond
> what the TLB in your processor is comfortable with.
BTW, by default, netperf will allocate a "ring" of send buffers - the number
allocated will be one more than the socket buffer size divided by the send size
- so in the example above, there will be two 32KB buffers allocated in netperf's
send ring. A similar calculation may happen on the receive side.
That can be controlled via the global (before the "--") -W option.
-W send,recv Set the number of send,recv buffers
So, you might make the netperf command:
netperf -t TCP_STREAM -H <remote> -l 30 -W 1,1 -- -s 32K -S 32K -m 32K
happy benchmarking,
rick jones
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