Re: 2.5.2-pre performance degradation on an old 486

From: Davide Libenzi (
Date: Mon Jan 07 2002 - 13:36:08 EST

On Mon, 7 Jan 2002, Mikael Pettersson wrote:

> 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.

I'll post a patch to Linus in 20 minutes otherwise Linus simply


current->dyn_prio = -100;

- Davide

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