Hyperthreading slowdown

[Kris Kennaway]

On Sat, Oct 04, 2003 at 04:39:03PM +0200, Mikulas Patocka wrote:
> Hi
> 
> 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
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