Date: Tue, 13 Apr 2010 08:21:53 +0900 (JST) From: Maho NAKATA <chat95@mac.com> To: bms@incunabulum.net Cc: freebsd-stable@freebsd.org Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 Message-ID: <20100413.082153.866357745773635148.chat95@mac.com> In-Reply-To: <4BC2EC9A.2020207@incunabulum.net> References: <20100412.131213.4959786962516027.chat95@mac.com> <4BC2EC9A.2020207@incunabulum.net>
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Hi Bruce, From: Bruce Simpson <bms@incunabulum.net> Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 Date: Mon, 12 Apr 2010 10:49:14 +0100 > So, where's the profiling to discover why this is the case? Ok I'll provide better documentation so that everyone can test it very clearly. (may take some time...) > Also I'm not clear on what constitutes 'theoretical peak performance' > here or how it is being calculated. So figures like these come across > as unscientific. Core i7 920 (2.66GHz) constitutes four cores. each core has four floating point operators. thus; 2.66GHz x 4 x 4 = 42.56Gflops cf. http://www.intel.com/support/processors/sb/cs-023143.htm > I'm sure this is something which can be resolved if someone sits down, > profiles the app, and makes the necessary adjustments > (e.g. pthread_setaffinity_np()) to configure CPU affinity, if the lack > of it is pessimizing your friend's app. might be. we run on the same machine. > The PMC framework is rapidly maturing, and you can use KCacheGrind > with it to visualize context switch overhead. > > But I think it's expecting a bit much to post informal results to > -stable, in an expectation of something other thaninformal suggestions > of what may help someone's maths-intensive application. BLAS is a basic linear algebra package which is used many applications. It is also used for top500 http://www.top500.org/ cf. http://www.top500.org/project/introduction via LINPACK. dgemm is LEVEL 3 BLAS, which is a very good for common PCs as calculation is CPU intensive. > If there are performance issues, then reproducible results are needed, > as well as some basic profiling effort of the system elements > involved, before people could say anything either way, or offer > further help. again, I'll provide better documentation so that everyone can test it very clearly. (may take some time...) thanks, -- Nakata Maho http://accc.riken.jp/maho/ , http://ja.openoffice.org/ Nakata Maho's PGP public keys: http://accc.riken.jp/maho/maho.pgp.txt
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