Messages in this thread |  | | Date | Wed, 28 Nov 2001 02:07:08 +0100 (CET) | From | Ingo Molnar <> | Subject | Re: Scheduler Cleanup |
| |
On Mon, 26 Nov 2001, Mike Kravetz wrote:
> I'm happy to see the cleanup of scheduler code that went into > 2.4.15/16. One small difference in behavior (I think) is that the > currently running task is not given preference over other tasks on the > runqueue with the same 'goodness' value. I would think giving the > current task preference is a good thing (especially in light of recent > discussions about too frequent moving/rescheduling of tasks). Can > someone provide the rational for this change? Was it just the result > of making the code cleaner? Is it believed that this won't really > make a difference?
i've done this change as part of the sched_yield() fixes/cleanups, and the main reason for it is that the current process is preferred *anyway*, due to getting the +1 boost via current->mm == this_mm in goodness().
(and besides, the percentage/probability of cases where we'd fail reselect a runnable process where the previous scheduler would reselect it is very very low. It does not justify adding a branch to the scheduler hotpath IMO. In 99.9% of the cases if a runnable process is executing schedule() then there is a higher priority process around that will win the next selection. Or if there is a wakeup race, then the process will win the selection very likely because it won the previous selection.)
Ingo
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |