Re: preempt-timing-2.6.8-rc1

Nick Piggin
2004-07-13T14:52:55Z

William Lee Irwin III wrote:
> On Tue, Jul 13, 2004 at 05:28:05AM -0700, William Lee Irwin III wrote:
>
>>>This patch uses the preemption counter increments and decrements to time
>>>non-preemptible critical sections.
>>>This is an instrumentation patch intended to help determine the causes of
>>>scheduling latency related to long non-preemptible critical sections.
>>>Changes from 2.6.7-based patch:
>>>(1) fix unmap_vmas() check correctly this time
>>>(2) add touch_preempt_timing() to cond_resched_lock()
>>>(3) depend on preempt until it's worked out wtf goes wrong without it
>
>
> On Tue, Jul 13, 2004 at 10:36:00AM -0400, Joe Korty wrote:
>
>>You preemption-block hold times will improve *enormously* if you move all
>>softirq processing down to the daemon (and possibly raise the daemon to
>>one of the higher SCHED_RR priorities, to compensate for softirq processing
>>no longer happening at interrupt level).
>
>
> Plausible. Got a patch?
>

Make MAX_SOFTIRQ_RESTART 1?

I don't think you should make ksoftirq a realtime task, because that
defeats the purpose of having it to prevent livelocking userspace
doesn't it?

However, you may want to increase it from nice +19. Probably just to
nice 0 would be an idea.