Re: 2.6.0-test2-mm3 osdl-aim-7 regression

[Nick Piggin <piggin@cyberone.com.au>]

Con Kolivas wrote:

>On Thu, 7 Aug 2003 18:25, Nick Piggin wrote:
>
>>>The more frequently you round robin the lower the scheduler latency
>>>between SCHED_OTHER tasks of the same priority. However, the longer the
>>>timeslice the more benefit you get from cpu cache. Where is the sweet
>>>spot? Depends on the hardware and your usage requirements of course, but
>>>Ingo has empirically chosen 25ms after 50ms seemed too long. Basically
>>>cache trashing becomes a real problem with timeslices below ~7ms on
>>>modern hardware in my limited testing. A minor quirk in Ingo's original
>>>code means _occasionally_ a task will be requeued with <3ms to go. It
>>>will be interesting to see if fixing this (which O12.2+ does) makes a big
>>>difference or whether we need to reconsider how frequently (if at all) we
>>>round robin tasks.
>>>
>>Why not have it dynamic? CPU hogs get longer timeslices (but of course
>>can be preempted by higher priorities).
>>
>
>Funny you should say that. Before Ingo merged his A3 changes, that's what my 
>version of them did.
>
>

Between you and me, I think this would be the right way to go if it
could be done right. I don't think wli, mjb and the rest of their
clique appreciate the 25ms reschedule!