Subject: Re: [linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch
From: Ingo Molnar (mingo_AT_elte.hu)
Date: Thu Jul 22 2004 - 10:07:44 EEST
* Nick Piggin <nickpiggin_AT_yahoo.com.au> wrote:
> Given that we're looking for something acceptable for 2.6, how about
> adding
>
> if (rt_task(current))
> kick ksoftirqd instead
>
> Otherwise, what is the performance penalty of doing all softirq
> processing from ksoftirqd?
this is insufficient too. An RT task might be _waiting to run_ and
spending our time in a non-RT context (including the idle task) doing
softirq processing might delay it indefinitely.
what we could do is to add a rq->nr_running_rt and do the deferred
softirq processing unconditionally if (rq->nr_running_rt). I'd still add
a sysctl to make it unconditional for user processes too - if someone
really cares about latency and doesnt want to make all his tasks RT.
I'll code this up for the next version of the patch.
Ingo
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