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Date: Wed, 14 Jul 2004 00:52:45 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: William Lee Irwin III <wli@holomorphy.com>
CC: Joe Korty <joe.korty@ccur.com>, linux-kernel@vger.kernel.org
Subject: Re: preempt-timing-2.6.8-rc1
References: <20040713122805.GZ21066@holomorphy.com> <20040713143600.GA22758@tsunami.ccur.com> <20040713144028.GH21066@holomorphy.com>
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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.