Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920

[Bruce Simpson]

Hi all,

There's a port archivers/pbzip2, and I am inclined to believe this is a 
good benchmark for multi-core performance in real-world usage (with an 
appropriate input data set).

BZIP2 is a compression algorithm which is readily applicable to 
multicore, because of the nature in which its workload may be partioned 
amongst multiple CPU cores. It block-sorts, and it can compress long 
runs of input data independently of other CPU threads.

When I used PBZIP2 informally back in January, before advising on 
FreeBSD/Xen, I saw largely the results I'd expect to see from such a 
workload, and didn't encounter pessimization of benchmark figures. 
Informal tests were performed on 8-STABLE at that time.

The OP may well be looking for Newton-Raphson approximations, to the 
derivatives involved in his friend's linear algebra system. The point is 
that PBZIP2 would also exercise context switches in a real-life workload.

I'd be concerned, as anyone else would be, about benchmarks which 
apparently challenge FreeBSD's ability to tackle significant 
mathematical workloads. But from what little I understand, from speaking 
to David Schultz and others who have been involved with FreeBSD's 
floating point performance, on a scientific basis -- without a 
scientifically reproducible experiment, I don't see a problem.

Obviously, I am concerned that Nakata-san observes what he regards to be 
a problem, and would like to help any way I can.

cheers,
BMS