linux-kernel - Re: [patch] CFS scheduler, -v6

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Date:	Fri, 27 Apr 2007 15:39:04 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Kasper Sandberg <lkml@...anurb.dk>,
	Gene Heskett <gene.heskett@...il.com>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Con Kolivas <kernel@...ivas.org>,
	Nick Piggin <npiggin@...e.de>, Mike Galbraith <efault@....de>,
	Arjan van de Ven <arjan@...radead.org>,
	Peter Williams <pwil3058@...pond.net.au>, caglar@...dus.org.tr,
	Willy Tarreau <w@....eu>, Mark Lord <lkml@....ca>,
	Zach Carter <linux@...hcarter.com>,
	buddabrod <buddabrod@...il.com>
Subject: Re: [patch] CFS scheduler, -v6

On Fri, 2007-04-27 at 13:55 +0200, Ingo Molnar wrote:
> * Ingo Molnar <mingo@...e.hu> wrote:
> 
> > update for lkml readers: this is some really 'catastrophic' condition 
> > triggering on your box. Here ogg123 just never skips on an older 750 
> > MHz box, which is 4-5 times slower than your 2GHz box - while i have 
> > _fourty nice-0 infinite loops_ running. I.e. at this clearly 
> > ridiculous load, at just 2.5% of CPU time ogg123 is just chugging 
> > along nicely and never leaves out a beat.
> 
> Kasper, just to exclude the possibility that this is somehow related to 
> IO scheduling, could you copy the OGG file over to /dev/shm and play it 
> from there? Do you still get the bad skips?

That's what I can observe here:

ogg123 local harddisk	skips
ogg123 nfs		works
ogg123 /dev/shm		works

The skips when running from the local harddisk are definitely caused by
the I/O scheduler or some other bottleneck in the block/disk/scsi/sata
jungle. I try to find out more details.

	tglx


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