linux-kernel - Re: Network slowdown due to CFS

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Message-Id: <1190802032.7318.1.camel@Homer.simpson.net>
Date:	Wed, 26 Sep 2007 12:20:32 +0200
From:	Mike Galbraith <efault@....de>
To:	Martin Michlmayr <tbm@...ius.com>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Network slowdown due to CFS

On Wed, 2007-09-26 at 10:52 +0200, Martin Michlmayr wrote:
> I noticed that my network performance has gone down from 2.6.22
> >from   [  3]  0.0-10.0 sec    113 MBytes  95.0 Mbits/sec
> to     [  3]  0.0-10.0 sec   75.7 MBytes  63.3 Mbits/sec
> with 2.6.23-rc1 (and 2.6.23-rc8), as measured with iperf.

FWIW, on my box blasting localhost, I see the opposite, repeatably.

root@...er: iperf -v
iperf version 2.0.2 (03 May 2005) pthreads

2.6.22.1-smp
for i in `seq 1 3`; do iperf -c localhost; done >> /xx

------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 21383 connected with 127.0.0.1 port 5001
[  3]  0.0-10.1 sec    518 MBytes    432 Mbits/sec
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 21384 connected with 127.0.0.1 port 5001
[  3]  0.0-10.0 sec    325 MBytes    273 Mbits/sec
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 21385 connected with 127.0.0.1 port 5001
[  3]  0.0-10.0 sec    434 MBytes    363 Mbits/sec

2.6.23-rc8-smp-d
for i in `seq 1 3`; do iperf -c localhost; done >> /xx

------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 11650 connected with 127.0.0.1 port 5001
[  3]  0.0-10.0 sec  2.01 GBytes  1.72 Gbits/sec
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 11651 connected with 127.0.0.1 port 5001
[  3]  0.0-10.0 sec  2.02 GBytes  1.74 Gbits/sec
------------------------------------------------------------
Client connecting to localhost, TCP port 5001
TCP window size: 49.2 KByte (default)
------------------------------------------------------------
[  3] local 127.0.0.1 port 11652 connected with 127.0.0.1 port 5001
[  3]  0.0-10.0 sec  2.10 GBytes  1.81 Gbits/sec


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