Re: [patch] 2.5.2 scheduler code for 2.4.18-pre1 ( was 2.5.2-pre performance degradation on an old 486 )

From: J.A. Magallon (
Date: Mon Jan 07 2002 - 09:35:33 EST

On 20020107 Andrea Arcangeli wrote:
>yes please (feel free to CC me on the answers), I'd really like to
>reduce the scheduler O(N) overhead to the number of the running tasks,
>rather than doing the recalculate all over the processes in the machine.
>O(1) scheduler would be even better of course, but the below would
>ensure not to hurt the 1 task running case, and it's way simpler to
>check for correctness (so it's easier to include it as a start).

It looks like you all are going to turn the scheduler upside-down.
Hmm, as a non-kernel-hacker observer from the world outside, could I
make a suggestion ?
Is it easy to split the thing in steps:
- Move from single-queue to per-cpu-queue, with just the same algorithm
  that is running now for per-queue scheduling.
- Get that running for 2.18.18 and 2.5.2
- Then start to play with the per-queue scheduling algorithm:
        * better O(n)
        * O(1)
        * O(1) with different queues for RT and non RT

Is it easy enough or are both steps so related that can not be split ?


(a linux user that tries experimental kernels and is seeing them grow
like mushrooms in latest weeks...)

J.A. Magallon                           #  Let the source be with you...
Mandrake Linux release 8.2 (Cooker) for i586
Linux werewolf 2.4.18-pre1-beo #1 SMP Fri Jan 4 02:25:59 CET 2002 i686
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