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Re: Should i turn off my intel HT?

cwinl wrote:
> my server is dual P4 Xeon 2.8G with HT tech.
> someone told me that i should turn off HT because of bad performance.
> i'd never heard about that before.
> is it a good advice and worth to do that right now?

What I really recommend is that you should benchmark your system and
determine that for yourself.  Run first one task.  Then two tasks
simultaneously.  Then three and so on.  Try that both with
hyperthreading on and then with it off.

What I found is that the first two logical cpus were on the same
physical cpu.  So two running tasks would be located there.  Each
would run at half speed because they each get only half of a physical
cpu.  The other cpu in the dual cpu system would be idle until a third
task came along at which it would run that task at full speed.
Hyperthreading was actually hurting a multi-cpu system because the
kernel task scheduler did not know about it.  This was with linux 2.4
and I do not know if 2.6 improves upon the situation.


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