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SubjectRe: [PATCH] Nick's scheduler policy


Martin J. Bligh wrote:

>Seems to do badly with CPU intensive tasks:
>
>Kernbench: (make -j vmlinux, maximal tasks)
> Elapsed System User CPU
> 2.6.0-test3 46.00 115.49 571.94 1494.25
> 2.6.0-test4-nick 49.37 131.31 611.15 1500.75
>

Thanks Martin.

>
>Oddly, schedule itself is significantly cheaper, but you seem
>to end up with much more expense elsewhere. Thrashing tasks between
>CPUs, maybe (esp given the increased user time)? I'll do a proper
>baseline against test4, but I don't expect it to be any different, really.
>

Yeah I'd say most if not all would be my fault though. What happens
is that a lowest priority process will get a 1ms timeslice if there
is a highest priority process on the same runqueue, though it will
get I think 275ms if there are only other low priority processes
there.

A kernbench probably has enough IO to keep priorities up a bit and
keep timeslices short. The timeslice stuff could probably still use
a bit of tuning. On the other hand, nice -20 processes should get
big timeslices, while other schedulers give them small timeslices.


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