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SubjectRe: [RFC][PATCH] Make MAX_RT_PRIO and MAX_USER_RT_PRIO configurable
Esben Nielsen wrote:
> On Wed, 27 Jul 2005, Ingo Molnar wrote:
>
>
>>* Steven Rostedt <rostedt@goodmis.org> wrote:
>>
>>
>>>Perfectly understood. I've had two customers ask me to increase the
>>>priorities for them, but those where custom kernels, and a config
>>>option wasn't necessary. But since I've had customers asking, I
>>>thought that this might be something that others want. But I deal
>>>with a niche market, and what my customers want might not be what
>>>everyone wants. (hence the RFC in the subject).
>>>
>>>So if there are others out there that would prefer to change their
>>>priority ranges, speak now otherwise this patch will go by the waste
>>>side.
>>
>>i'm not excluding that this will become necessary in the future. We
>>should also add the safety check to sched.h - all i'm suggesting is to
>>not make it a .config option just now, because that tends to be fiddled
>>with.
>>
>
> Isn't there a way to mark it "warning! warning! dangerous!" ?
>
> Anyway: I think 100 RT priorities is way overkill - and slowing things
> down by making the scheduler checking more empty slots in the runqueue.
> Default ought to be 10. In practise it will be very hard to have
> a task at the lower RT priority behaving real-time with 99 higher
> priority tasks around. I find it hard to believe that somebody has an RT
> app needing more than 10 priorities and can't do with RR or FIFO
> scheduling within a fewer number of prorities.
>
> Esben
>

Actually, is it really that slow to search a bitmap for a slot that
needs processing? I work on real-time test stands which are less of an
embedded system and more of a real Unix system that require determinism.
It is very nice in some cases to have more than 10 RT priorities to work
with.

--
kr
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