linux-kernel - Re: CFS review

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Message-ID: <20070828073619.GA8267@elte.hu>
Date:	Tue, 28 Aug 2007 09:36:19 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Mike Galbraith <efault@....de>
Cc:	Al Boldi <a1426z@...ab.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: CFS review


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

> > I like your analysis, but how do you explain that these stalls 
> > vanish when __update_curr is disabled?
> 
> When you disable __update_curr(), you're utterly destroying the
> scheduler.  There may well be a scheduler connection, but disabling
> __update_curr() doesn't tell you anything meaningful.  Basically, you're
> letting all tasks run uninterrupted for just as long as they please
> (which is why busy loops lock your box solid as a rock).  I'd suggest
> gathering some sched_debug stats or something... [...]

the output of the following would be nice:

  http://people.redhat.com/mingo/cfs-scheduler/tools/cfs-debug-info.sh

captured while the gears are running.

	Ingo
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