> > > >---- Original Message ---- >From: rei...@bellatlantic.net >To: debian-user@lists.debian.org >Subject: Re: Debian stock kernel config -- CONFIG_NR_CPUS=32? >Date: Fri, 22 Oct 2010 20:05:49 -0400 > >>On Friday 22 October 2010 11:34:19 ow...@netptc.net wrote: >> >>> In fact IIRC the additional overhead follows the square of the >number >>> of CPUs. I seem to recall this was called Amdahl's Law after Gene >>> Amdahl of IBM (and later his own company) >> >> Either that's not it, or there's more than one "Amdahl's law" -- >>the oen I know is about diminishing returns from increasing effort >>to parallelize code. I don't know it in its pithy form, but >>the gist of it is that you can only parallelize *some* of your >>code, because all algorithms have a certain amount of set-up >>and tear-down overhead that's typically serial. Even if you >>perfectly parallelize the parallelizable part of the code, >>so it runs N times faster, your application as a whole will >>run something less than N times faster, and as N gets large, >>this "serial offset" contribution will come to dominate the >>execution time, at which point additional investments in >>parallelization are probably wasted. >> Actually Amdahl's Law IS a law of diminishing returns but is intended to be applied to hardware, not software. The usual application is to compute the degree to which adding another processor increases the processing power of the system Larry >> -- A. >>-- >>Andrew Reid / rei...@bellatlantic.net >> >> >>-- >>To UNSUBSCRIBE, email to debian-user-requ...@lists.debian.org >>with a subject of "unsubscribe". Trouble? Contact >listmas...@lists.debian.org >>Archive: http://lists.debian.org/201010222005.49579.rei...@bellatlan >tic.net >> >>
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