Hi Antony I think this is not the case. I tested TurboBoost on/off on Ubuntu, GotoBLAS achieved 95% of theoretical perfomance for both cases.
cf. http://www.intel.com/support/processors/sb/cs-023143.htm and http://blog.goo.ne.jp/nakatamaho/e/86c0f4ac529fd5b530454ed795e6b466 (written in Japanese, tho) Thanks From: Antony Mawer <[email protected]> Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 Date: Mon, 12 Apr 2010 23:58:17 +1000 > This may well be the same sort of issue that was discussed in this thread > here: > > http://lists.freebsd.org/pipermail/freebsd-hackers/2010-March/031004.html > > In short, the Core i7 CPUs have a feature called "TurboBoost" where > the clock speed of one or more cores is boosted when other cores are > idle and in a C2 or C3 sleep status ... if the appropriate power > saving mode isn't active on the system (which I don't think FreeBSD > does by default?), the idle cores are never put into the appropriate > power saving state, and as a result TurboBoost never kicks in... > > It _may_ be that Ubuntu configures this correctly whereas FreeBSD does > not (out of the box)? > > Of course it may be something else entirely, but worth checking out... > > --Antony > > On Mon, Apr 12, 2010 at 7:31 PM, Adrian Chadd <[email protected]> wrote: >> Of course, what would be helpful is actually figuring out what is >> going on rather than some conjecture. :) >> >> With what he said, tweaking memory allocation under FreeBSD and/or >> linux would change the performance characteristics and either validate >> or disprove his assumptions? >> >> >> Adrian >> >> On 12 April 2010 12:12, Maho NAKATA <[email protected]> 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 amd64 >>> using dgemm >>> (a linear algebra routine, matrix-matrix multiplication). >>> I obtained only 70% of theoretical peak performance on FreeBSD 8/amd64 and >>> 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 >>> computing. 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 still >>>> not very will >>>> sophisticated, but on *BSDs, its worst; they uses too fine memory >>>> allocation 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 kind >>>> 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 : FLOPS : percent in peak >>> FreeBSD : 32.0 GFlops : 71% >>> Ubuntu : 42.0-42.7GFlops : 93.8%-95.3% >>> >>> 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 >>> >>> >>> >>> >>> _______________________________________________ >>> [email protected] mailing list >>> http://lists.freebsd.org/mailman/listinfo/freebsd-stable >>> To unsubscribe, send any mail to "[email protected]" >>> >> _______________________________________________ >> [email protected] mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-stable >> To unsubscribe, send any mail to "[email protected]" >> > _______________________________________________ > [email protected] mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-stable > To unsubscribe, send any mail to "[email protected]" > _______________________________________________ [email protected] mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-stable To unsubscribe, send any mail to "[email protected]"
