No "last core parallel slowdown" on OS X
Manuel M T Chakravarty
chak at cse.unsw.edu.au
Sun Apr 19 05:58:46 EDT 2009
> In that paper, they routinely benchmark N-1 cores on an N core Linux
> box, because of a noticeable falloff using the last core, which can
> do more harm than good. I had confirmed this on my four core Linux
> box, but was puzzled that my two core MacBook showed no such
> falloff. Hey, two cores isn't representative of many cores, cache
> issues yada yada, so I waited.
> Compared to 2 cores, using 3, 4 cores on an equivalent four core box
> running OS X gives speedups of
> 1.45x, 1.9x
As another data point, in our work on Data Parallel Haskell, we ran
benchmarks on an 8-core Xserve (OS X) and an 8-core Sun T2 (Solaris).
On both machines, we had no problem using all 8 cores.
More information about the Glasgow-haskell-users