linux-kernel - Re: [git pull] scheduler fixes

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Message-ID: <20090117161222.GC31601@elte.hu>
Date:	Sat, 17 Jan 2009 17:12:22 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Galbraith <efault@....de>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [git pull] scheduler fixes


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

> Dunno about the IO bits, but..
>  
> The problem with the C++ testcases seems to be wake_up_all() plunking a 
> genuine thundering herd onto runqueues.  The sleeper fairness logic 
> places the entire herd left of min_vruntime, meaning N*sched_latency 
> pain for the poor sods who are setting the runqueue pace.

100 wakeup pairs that all run and ping-pong between each other?

That creates 200 tasks with an average system load of 100.0, on a 
dual-core system. Is that a fair representation of some real workload, or 
just an unrealistic "gee, look, given enough tasks running I can overload 
the system _this bad_" example?

	Ingo
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