Re: Priority for SMP VMs

[Jeremy Fitzhardinge <jeremy@goop.org>]

George Dunlap wrote:
> If you want a "clean" scheduler test, you should instead run "while(1)
> ;" loops, which will never block, and will always consume all cpu time
> available.  My guess is if you do that, then the cpu time given to
> each domain will be exactly according to their weight.  On the other
> hand, if you do a "kernbench" test, which will include a lot of
> blocking, I suspect you may get even more disparity between the
> runtimes.
>   

My experience is that kernbench, if run properly, should not block.  It 
precaches the source in memory before starting, so it should not 
generate any reads during a benchmark run.  It will still write the 
build products, but write-behind should make that non-blocking from the 
benchmark's perspective.

Running the maximal "make -j" test without enough memory will drive the 
machine into swapstorm, which will definitely block, but you're supposed 
to run with enough memory to avoid that (~4G bytes, I think).

    J