Re: [PATCH] O10int for interactivity

From: Valdis.Kletnieks@vt.edu
Date: Mon Jul 28 2003 - 13:08:12 EST


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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