Re: [PATCH] O10int for interactivity

From: Valdis.Kletnieks@vt.edu
To: Con Kolivas <kernel@kolivas.org>
Cc: linux kernel mailing list <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH] O10int for interactivity
Date: Mon, 28 Jul 2003 14:08:12 -0400	[thread overview]
Message-ID: <200307281808.h6SI8C5k004439@turing-police.cc.vt.edu> (raw)
In-Reply-To: Your message of "Mon, 28 Jul 2003 01:12:16 +1000." <200307280112.16043.kernel@kolivas.org>

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On Mon, 28 Jul 2003 01:12:16 +1000, Con Kolivas said:
> Here is a fairly rapid evolution of the O*int patches for interactivity thanks
> to Ingo's involvement.

I'm running the -O10 variant that's in Andrew's -test2-mm1 patch, and I'm
totally unable to force the CPU scheduler to misbehave.

I am, however, able to get 'xmms' to skip.  The reason is that the CPU is being
scheduled quite adequately, but I/O is *NOT*.

The reason is that xmms's .ogg decoder is reading a 128K chunk every 10 seconds
or so, and doesn't do the next read till it's *really* close to running out of
data.  Unfortunately, under high I/O load (which isn't all THAT high, it's a
HITACHI_DK23DA-40 in a Dell Laptop) it's possible for that 128K read to get
stuck behind other stuff that's doing heavy I/O (for instance, starting Mozilla
or OpenOffice, or sometime a 'find' command).

I'm guessing that the anticipatory scheduler is the culprit here.  Soon as I figure
out the incantations to use the deadline scheduler, I'll report back....

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