Messages in this thread | | | Date | Fri, 28 Mar 2008 14:59:47 +0100 | From | Pavel Machek <> | Subject | Re: performance differences: "maxcpus=1" vs. "echo 0 > /sys/devices/system/cpu/cpu1/online" |
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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
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