Re: [PATCH] Nick's scheduler policy

[Nick Piggin]

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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