Re: Network slowdown due to CFS

From: Ingo Molnar
Date: Wed Sep 26 2007 - 05:35:35 EST

* Martin Michlmayr <tbm@xxxxxxxxxx> 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.
> I did a git bisect today and tracked it back to the commit where CFS
> was enabled ("sched: cfs core code; apply the CFS core code",
> commit dd41f596cda0d7d6e4a8b139ffdfabcefdd46528). I also compiled a
> kernel from
> git://
> but things don't improve.
> This is on a Thecus N2100, an ARM (Intel IOP32x) based storage device
> with a r8169 card, SATA disks and 512 MB RAM. My config is attached.
> What kind of information can I supply so you can track this down?

as a starter, could you boot the sched-devel.git kernel, with
CONFIG_SCHED_DEBUG=y and CONFIG_SCHEDSTATS=y enabled and could you run
this script while the iperf test is in the middle of its testrun:

this will gather a good deal of info about the workload in question.
Please send me the resulting debug file.

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