linux-kernel - Re: Network slowdown due to CFS

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Message-ID: <20070926112919.GN3337@deprecation.cyrius.com>
Date:	Wed, 26 Sep 2007 13:29:19 +0200
From:	Martin Michlmayr <tbm@...ius.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Mike Galbraith <efault@....de>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org,
	Stephen Hemminger <shemminger@...ux-foundation.org>
Subject: Re: Network slowdown due to CFS

* Ingo Molnar <mingo@...e.hu> [2007-09-26 13:21]:
> > > I noticed on the iperf website a patch which contains sched_yield().
> > > http://dast.nlanr.net/Projects/Iperf2.0/patch-iperf-linux-2.6.21.txt
> 
> great! Could you try this too:
>    echo 1 > /proc/sys/kernel/sched_compat_yield
> 
> does it fix iperf performance too (with the yield patch applied to
> iperf)?

Yes, this gives me good performance too.

> I think the real fix would be for iperf to use blocking network IO
> though, or maybe to use a POSIX mutex or POSIX semaphores.

So it's definitely not a bug in the kernel, only in iperf?

(CCing Stephen Hemminger who wrote the iperf patch.)
-- 
Martin Michlmayr
http://www.cyrius.com/
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