[linux-audio-dev] Re: [announce] [patch] Voluntary Kernel Preemption Patch

[Nick Piggin]

Ingo Molnar wrote:
> * Nick Piggin <nickpiggin at yahoo.com.au> wrote:
> 
> 
>>What do you think about deferring softirqs just while in critical
>>sections?
>>
>>I'm not sure how well this works, and it is CONFIG_PREEMPT only but in
>>theory it should prevent unbounded softirqs while under locks without
>>taking the performance hit of doing the context switch.
> 
> 
> i dont think this is sufficient. A high-prio RT task might be performing
> something that is important to it but isnt in any critical section. This
> includes userspace processing. We dont want to delay it with softirqs.
> 

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?