How to reproduce: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920

[Andriy Gapon]

on 14/04/2010 20:47 Adam Vande More said the following:
> I'm no expert Andriy, but it seems like if gotoblas
> implemented some of the FreeBSD optimizations then we'd be in the same
> ballpark.

This is a good point.
But on the other hand, it means that our scheduler doesn't do a perfect job
here.  BTW, I use ULE.
My observation is that when a number of CPU-intensive long running processes is
less than or equal to number of cores, then the processes tend to stay on the
same cores for a long time.
But if the number of the processes is greater, then they seem to jump from core
to core a lot.
But I am not sure what would be an optimal strategy for that case.  If we try to
keep some lucky processes on the same core, then cpu time might be shared
unfairly.  Shuffling cores provides more fairness, but can hurt total performance.

-- 
Andriy Gapon