linux-kernel - Re: Issues with Patch: "sched: Improve latencies and throughput"

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Message-Id: <1270100986.6707.156.camel@marge.simson.net>
Date:	Thu, 01 Apr 2010 07:49:46 +0200
From:	Mike Galbraith <efault@....de>
To:	Michael Grzeschik <mgr@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, rsc@...gutronix.de
Subject: Re: Issues with Patch: "sched: Improve latencies and throughput"

On Thu, 2010-04-01 at 00:31 +0200, Michael Grzeschik wrote:
> We are using an arm mx31 embedded cpu with the v2.6.34 Kernelrelease and
> realized some issues with the scheduling behaviour the patch "sched:
> Improve latencies and throughput" [1] by Mike Galbraith introduced to
> the kernel.
> 
> When we used the alsa utility aplay to pipe some audio through an
> usbaudio device and put some scheduling overhead on the device, the
> amount of underruns, due to the not fast enough refilled ring buffer,
> was noticable increased with that patch [1] applied. Until we reverse
> applied the patch the amount of underruns was appreciable lower.

Testcase?

> That in fact is the opposite behaviour to its actual meaning.

Not necessarily.  NEXT_BUDDY can increase latency for waiters, as can
_not_ pulling a waiter to an idle CPU. 


> [1] 0ec9fab3d186d9cbb00c0f694d4a260d07c198d9
> 
> mgr

	-Mike

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