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Message-ID: <20080328135946.GB4404@ucw.cz> Date: Fri, 28 Mar 2008 14:59:47 +0100 From: Pavel Machek <pavel@....cz> To: Michael Meyer <mike65134@...oo.de> Cc: linux-kernel@...r.kernel.org Subject: Re: performance differences: "maxcpus=1" vs. "echo 0 > /sys/devices/system/cpu/cpu1/online" On Tue 2008-03-25 14:47:50, Michael Meyer wrote: > Hi, > > what is the difference between booting a dual core > machine with "maxcpus=1" or by deactivating the second > core at run time with "echo 0 > > /sys/devices/system/cpu/cpu1/online"? maxcpus=1 : core stays powered off 0 > online : core enters halt. > I observed a funny behaviour of apache ant: although > it uses javac which is single threaded, a compile run > with "maxcpus=1" is actually faster than a compile run > with both cores activated. But with the second core > deactivated using "echo 0 > > /sys/devices/system/cpu/cpu1/online" it is even slower > than with both cores. Thermal fun? Check cooling. > Is here any method to get the exact same behaviour of > "maxcpus=1" with disabling the second core only > temporarily? So that the second core could be disabled > before the ant execution and enabled after the ant > execution? Patch pushing 0 > online cores into C4 would be nice. -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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