Nice 19 process still gets some CPU

[Timothy Miller <miller@techsource.com>]

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?

Thanks.