Date: Mon, 15 Sep 2008 19:36:43 -0500 From: Stephen Montgomery-Smith <stephen@math.missouri.edu> To: cpghost <cpghost@cordula.ws> Cc: freebsd-current@freebsd.org Subject: Re: Improved multiprocessor usage on amd64 Message-ID: <48CEFF9B.2080505@math.missouri.edu> In-Reply-To: <20080915185446.GB69615@phenom.cordula.ws> References: <48CDBC78.4010409@math.missouri.edu> <20080915185446.GB69615@phenom.cordula.ws>
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cpghost wrote: > On Sun, Sep 14, 2008 at 08:38:00PM -0500, Stephen Montgomery-Smith wrote: >> I have a dual core amd64 on which I run a processor intensive numerical >> program. I had been frustrated because it seemed to run 3 or 4 times >> faster under Linux. But with a recent upgrade of FreeBSD-CURRENT, it >> now goes at about the same speed as Linux. >> >> The program takes about an hour. For the first minute, the program runs >> rather slowly, but then it is as if the operating system finds its way, >> and suddenly it speeds up. "top -H" suggests that for the first minute >> that one thread is going really slowly, and is perhaps being starved or >> something. >> >> My question is - why is this happening, and is this something I should >> expect? Are there certain switches or sysctls I can set to make it go >> fast from the get go? > > It looks like you're running powerd (see in /etc/rc.conf). It can take up > to a minute for the load average of the machine to exceed a certain > threshold where powerd would finally bump the cpu(s) to full speed. > > As for sysctls, check the speed with something like: > > # sysctl dev.cpu.0 Excellent idea! I should have thought of that myself. Unfortunately it didn't help much when I switched powerd off.
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