Re: Nice 19 process still gets some CPU

[Con Kolivas <kernel@kolivas.org>]

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Timothy Miller wrote:
| Given how much I've read here about schedulers, I should probably be
| able to answer this question myself, but I just thought I might talk to
| the experts.
|
| I'm running SETI@Home, and it has a nice value of 19.  Everything else,
| for the most part, is at zero.
|
| I'm running kernel gentoo-dev-sources-2.6.7-r6 (I believe).
|
| When I'm not running SETI@Home, compiler threads (emerge of a package,
| kernel compile, etc.) get 100% CPU.  When I AM running SETI@Home,
| SETI@Home still manages to get between 5% and 10% CPU.
|
| I would expect that nice 0 processes should get SO MUCH more than nice
| 19 processes that the nice 19 process would practically starve (and in
| the case of a nice 19 process, I think starvation by nice 0 processes is
| just fine), but it looks like it's not starving.
|
| Why is that?

It definitely should _not_ starve. That is the unixy way of doing
things. Everything must go forward. Around 5% cpu for nice 19 sounds
just right. If you want scheduling only when there's spare cpu cycles
you need a sched batch(idle) implementation.

Con
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