Date: Tue, 25 Sep 2007 15:14:40 +0530
From: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>, linux-kernel@vger.kernel.org,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Dhaval Giani <dhaval@linux.vnet.ibm.com>,
       Dmitry Adamushko <dmitry.adamushko@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [git] CFS-devel, latest code
Message-ID: <20070925094440.GK26289@linux.vnet.ibm.com>
Reply-To: vatsa@linux.vnet.ibm.com
References: <20070924214537.GA18980@elte.hu> <1190700652.6482.7.camel@Homer.simpson.net> <1190705759.11910.10.camel@Homer.simpson.net> <1190709207.11226.6.camel@Homer.simpson.net> <20070925091331.GA22905@elte.hu>
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On Tue, Sep 25, 2007 at 11:13:31AM +0200, Ingo Molnar wrote:
> 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?

Yep, I noticed that too.

check_preempt_wakeup()
{
	...

	if (is_same_group(curr, p)) {
	    ^^^^^^^^^^^^^

		resched_task();
	}

}

Will try a fix to check for preemption at higher levels ..

-- 
Regards,
vatsa
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