linux-kernel - Re: [git] CFS-devel, latest code

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Message-ID: <20070925091331.GA22905@elte.hu>
Date:	Tue, 25 Sep 2007 11:13:31 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Galbraith <efault@....de>
Cc:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>,
	Dhaval Giani <dhaval@...ux.vnet.ibm.com>,
	Dmitry Adamushko <dmitry.adamushko@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [git] CFS-devel, latest code

* Mike Galbraith <efault@....de> wrote:

> > sched_debug (attached) is.. strange.
> 
> Disabling CONFIG_FAIR_GROUP_SCHED fixed both.  [...]

heh. Evil plan to enable the group scheduler by default worked out as 
planned! ;-) [guess how many container users would do ... interactivity 
tests like you do??]

> [...] Latencies of up to 336ms hit me during the recompile (make -j3), 
> with nothing else running. Since reboot, latencies are, so far, very 
> very nice. [...]

'very very nice' == 'best ever' ? :-)

> [...] I'm leaving it disabled for now.

ok, i'm too seeing some sort of latency weirdness with 
CONFIG_FAIR_GROUP_SCHED enabled, _if_ there's Xorg involved which runs 
under root uid on my box - and hence gets 50% of all CPU time.

Srivatsa, any ideas? It could either be an accounting buglet (less 
likely, seems like the group scheduling bits stick to the 50% splitup 
nicely), or a preemption buglet. One potential preemption buglet would 
be for the group scheduler to not properly preempt a running task when a 
task from another uid is woken?

	Ingo
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