performance differences: "maxcpus=1" vs. "echo 0 > /sys/devices/system/cpu/cpu1/online"

[Michael Meyer <mike65134@yahoo.de>]

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"?

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.

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?

Thanks a lot!


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