linux-kernel - Re: High priority tasks break SMP balancer?

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Message-ID: <Pine.LNX.4.64.0711151206370.28639@schroedinger.engr.sgi.com>
Date:	Thu, 15 Nov 2007 12:07:47 -0800 (PST)
From:	Christoph Lameter <clameter@....com>
To:	Micah Dowty <micah@...are.com>
cc:	Kyle Moffett <mrmacman_g4@....com>,
	Cyrus Massoumi <cyrusm@....net>,
	LKML Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Andrew Morton <akpm@...l.org>,
	Mike Galbraith <efault@....de>, Paul Menage <menage@...gle.com>
Subject: Re: High priority tasks break SMP balancer?

On Thu, 15 Nov 2007, Micah Dowty wrote:

> For reference, the exact test I used with git-bisect is attached. The
> C program (priosched) starts two busy-looping threads and a
> high-priority high-frequency thread which uses relatively little
> CPU. The Python program repeatedly starts the C program, runs it for a
> half second, and measures the resulting imbalance in CPU usage. On
> kernels prior to the above commit, this reports values within about
> 10% of 1.0. On later kernels, it crashes within a couple iterations
> due to a divide-by-zero error :)

The kernel crashes? Sounds like your application crashes with a divide by 
zero?


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