Messages in this thread | | | From | Con Kolivas <> | Subject | Re: [PATCH] 2.6.0 batch scheduling, HT aware | Date | Tue, 23 Dec 2003 14:15:38 +1100 |
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On Tue, 23 Dec 2003 13:57, Nick Piggin wrote: > Con Kolivas wrote: > >On Tue, 23 Dec 2003 12:36, Nick Piggin wrote: > >>Con Kolivas wrote: > >>>I discussed this with Ingo and that's the sort of thing we thought of. > >>>Perhaps a relative crossover of 10 dynamic priorities and an absolute > >>>crossover of 5 static priorities before things got queued together. This > >>>is really only required for the UP HT case. > >> > >>Well I guess it would still be nice for "SMP HT" as well. Hopefully the > >>code can be generic enough that it would just carry over nicely. > > > >I disagree. I can't think of a real world scenario where 2+ physical cpus > >would benefit from this. > > Well its the same problem. A nice -20 process can still lose 40-55% of its > performance to a nice 19 process, a figure of 10% is probably too high and > we'd really want it <= 5% like what happens with a single logical > processor.
I changed my mind just after I sent that mail. 4 physical cores running three nice 20 and one nice -20 task gives the nice -20 task only 25% of the total cpu and 25% to each of the nice 20 tasks.
> >>It does > >>have complications though because the load balancer would have to be > >> taught about it, and those architectures that do hardware priorities > >> probably don't even want it. > > > >Probably the simple relative/absolute will have to suffice. However it > > still doesn't help the fact that running something cpu bound concurrently > > at nice 0 with something interactive nice 0 is actually slower if you use > > a UP HT processor in SMP mode instead of UP. > > It will be based on dynamic priorities, possibly with some feedback from > nice as well, but it probably still won't be perfect and it will probably > be very complex *cough* hardware priorities *cough* ;) > > I might try to fit it into a more general priority balancing system because > we currently have similar sorts of failings on regular SMP as well.
I'll keep my eyes peeled. Meanwhile I'll use my ugly patch ;-)
Con
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