Re: [RFC] CPU scheduler: Simplified interactive bonus mechanism

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Ingo Molnar wrote:
* Ingo Molnar <[email protected]> wrote:

* Peter Williams <[email protected]> wrote:

This patch implements a prototype version of a simplified interactive bonus mechanism. The mechanism does not attempt to identify interactive tasks and give them a bonus (like the current mechanism does) but instead attacks the problem that the bonuses are supposed to fix, unacceptable interactive latency, directly.

i think we could give this one a workout in -mm, to see the actual effects. Would you mind to merge this to -mm's scheduler queue, to right after sched-add-sched_batch-policy.patch?

i have done this for latest -mm, see the patch below (i also merged your patch to the SCHED_BATCH patch's effects), but the resulting kernel has really bad interactivity: e.g. simply starting 4 CPU hogs on a 2-CPU system slows down shell commands like 'ls' noticeably. So NACK for the time being.

I've just realized a more serious reason why this scheduler modification needs to be postponed as unsuitable for general use. It essentially relies on sched_clock() having at least microsecond resolution and it has been pointed out to me that on some systems this isn't true and, even though its units are always nanoseconds, the resolution of sched_clock() can be large as 1/HZ. This scheduler would not work very well on these systems so its time has not yet come regardless of successful resolution of the other problems.

Nevertheless, I'll add a scheduler based on ingosched with this modification (and fixes) to PlugSched so that progress can be made on improving it for those systems where it is feasible.

Peter Williams                                   [email protected]

"Learning, n. The kind of ignorance distinguishing the studious."
 -- Ambrose Bierce
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