Lee Revell wrote:
> On Sat, 2004-10-09 at 01:34, Con Kolivas wrote:
> 
>>Lee Revell wrote:
>>
>>>>>>>With VP and PREEMPT in general, does the scheduler always run the
>>>>>>>highest priority process, or do we only preempt if a SCHED_FIFO process
>>>>>>>is runnable?
>>>>>>
>>>>>>Always the highest priority runnable.
>>>>>>
>>>>>
>>>>>
>>>>>Hmm, interesting.  Would there be any advantage to a mode where only
>>>>>SCHED_FIFO tasks can preempt?  This seems like a much lighter way to
>>>>>solve the realtime problem.
>>>>
>>>>No, the linux scheduler has always been preemptible. PREEMPT and VP just 
>>>>allows it to preempt kernel code paths as well. It could be modified to 
>>>>do such a thing but apart from real time applications it would perform 
>>>>very badly overall.
>>>
>>>
>>>I am talking about a mode where we only allow a SCHED_FIFO process to
>>>preempt a kernel code path.  In every other case it works like !PREEMPT.
>>>
>>>This is apparently how kernel preemption worked on SVR4.
>>
>>Yes it could. If you ask nicely, Ingo might even throw in yet another 
>>config option in the kernel. It gets messy if multiple people start 
>>hacking on the same thing when it's under heavy development.
> 
> 
> Oh, I was not going to post a patch, I don't know the code nearly well
> enough at this point :-).  But it looks pretty straightforward.

I was talking about me ;-)

Cheers,
Con