Date: Tue, 13 Apr 2010 00:18:36 +0100 From: Bruce Simpson <bms@incunabulum.net> To: Jeremy Chadwick <freebsd@jdc.parodius.com>, freebsd-stable <freebsd-stable@freebsd.org> Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 Message-ID: <4BC3AA4C.30904@incunabulum.net> In-Reply-To: <20100412150023.GA80292@icarus.home.lan> References: <20100412.131213.4959786962516027.chat95@mac.com> <4BC3311F.5060503@icyb.net.ua> <20100412150023.GA80292@icarus.home.lan>
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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
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