Re: 2.5.2-pre performance degradation on an old 486

From: Mikael Pettersson (
Date: Mon Jan 07 2002 - 13:01:15 EST

On Mon, 7 Jan 2002 08:43:04 -0800 (PST), Linus Torvalds wrote:
>Hey, that would do it. It looks like the idle task ends up being a
>_normal_ process (just nice'd down), so it will get real CPU time instead
>of only getting scheduled when nothing else is runnable.
>Davide, I think the bounce-buffer is a red herring, it's simply that we're
>wasting time in idle..

This does seem to be the case. As a quick hack I added

        if (p == &init_task) return -50;

at the start of kernel/sched.c:goodness() [to approximate the old
scheduler's behaviour], and this immediately restored performance
on my 486 to the old scheduler's levels.

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