Date: Sun, 11 Apr 2010 21:47:46 -0700 From: Garrett Cooper <yanefbsd@gmail.com> To: Maho NAKATA <chat95@mac.com> Cc: freebsd-stable@freebsd.org Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 Message-ID: <u2q7d6fde3d1004112147t29915255nd6347d87e66d9dab@mail.gmail.com> In-Reply-To: <20100412.131213.4959786962516027.chat95@mac.com> References: <20100412.131213.4959786962516027.chat95@mac.com>
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On Sun, Apr 11, 2010 at 9:12 PM, Maho NAKATA <chat95@mac.com> wrote: > Hi FreeBSD developers, > [the original article in Japanese can be found at > http://blog.goo.ne.jp/nakatamaho/e/b5f6fbc3cc6e1ac4947463eb1ca4eb0a ] > > *Abstract* > I compared the peak performance of FreeBSD 8.0/amd64 and Ubuntu 9.10 amd6= 4 using dgemm > (a linear algebra routine, matrix-matrix multiplication). > I obtained only 70% of theoretical peak performance on FreeBSD 8/amd64 an= d > almost 95% on Ubuntu 9.10 /amd64. I'm really disappointed. > > *Introduction* > I'm a friend of Gotoh Kazushige, the principal developers of GotoBLAS. He= told me that > FreeBSD is not suitable OS for scientific computing or high performance c= omputing. He says > (in Japanese and my translation): > >> I guess FreeBSD does page coloring, but I don't think FreeBSD considers = very large cache >> size which recent CPU has. Support of a very large cache on Linux is sti= ll not very will >> sophisticated, but on *BSDs, its worst; they uses too fine memory alloca= tion method, >> so we cannot expect large continuous physical memory allocation. >> Moreover, process scheduling is not so nice as *BSD employs an algorithm= that >> changes physical CPUs in turn instead of allocating one core for such ki= nd of jobs. >> Take your own benchmark, and you'll see.. > > *Result* > Machine: Core i7 920 (42.56-44.8Gflops) / DDR3 1066 > OS: FreeBSD 8.0/amd64 and Ubuntu 9.10 > GotoBLAS2: 1.13 > > dgemm result > OS =A0 =A0 =A0: FLOPS =A0 =A0 =A0 =A0 =A0 : percent in peak > FreeBSD : 32.0 GFlops =A0 =A0 : 71% > Ubuntu =A0: 42.0-42.7GFlops : 93.8%-95.3% I'm not sure if this is the exact issue, but it might be a point of reference worth investigating: http://lists.freebsd.org/pipermail/freebsd-hackers/2010-March/031004.ht= ml Thanks, -Garrett
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