Re: preempt-timing-2.6.8-rc1

From: Nick Piggin
Date: Tue Jul 13 2004 - 09:53:53 EST


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.
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