On Sat, Oct 04, 2003 at 04:39:03PM +0200, Mikulas Patocka wrote:I installed FreeBSD 4.9RC1 on P4 3GHz with hyperthreading and I see drastic slowdown when kernel with hyperthreading is booted. For example program compilation took this time:
hyperthreading kernel, make -j 1 --- 1:09 hyperthreading kernel, make -j 2 --- 0:42 singlethreading kernel, make -j 1 --- 0:45 singlethreading kernel, make -j 2 --- 0:41
Compilation does very few system calls so when I compile with only one process (-j 1), it should be as fast as with singlethreading kernel. Do you have any idea why is it so slow?
Do you realise that hyperthreading != a secret extra CPU in your system?
Kris
I didn't see anywhere in the message where he implied that. To me, the interesting thing is that there is such a larger difference between the compile time for -j1 and -j2 when using hyperthreading as compared to the difference between -j1 and -j2 for a single threaded kernel. It's over a 50% slowdown.
Richard Coleman
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