Re: Stolen and degraded time and schedulers

Jeremy Fitzhardinge
2007-03-14T15:08:23Z

Lennart Sorensen wrote:
> How would you deal with something like a pentium 4 HT processor where
> you may run slower just because you got scheduled on the sibling of a
> cpu that happens to run something else needing the same execution units
> you do, causing you to get delayed more, even though the cpu is running
> full speed and nothing else is trying to use your "cpu"? I don't think
> there is any way to know what the real impact of two processes on a HT
> cpu have on each other.
>
> Interesting goal. Not sure it can be done.

You're right. That's a very tough case. I don't know if there's any
way to do a reasonable estimate of the slowdown. You could handwave it
and say "if both threads are running a process, then apply an X scaling
factor to their rate of progress". That might be enough.

J