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Re: hyperthreading or not



Emmanuel Fleury wrote:

Paul Brook wrote:
The only way to reliably tell is to try it.

Right.

Hyperthreading helps some things and hurts others.

I have an AMD64 hyperthreaded box at home and I don't see when it should
harm... :-/

The point of hyperthreading is to use unused ressources of the processor
for the second thread/process (the scheduler must be good enough to not
block everything).

Just an uneducated guess...

Regards
The problem with hyperthreading is that there's only a bare minimum of distinct hardware - almost all resources are shared. notably, a pipeline stall on one thread (where the pipelines on a p4 are ridiculously long) will flufh the hyperthread's pipeline too.

Hyperthreading gives an illusion of responsiveness on the desktop, but no vendor in their right minds ships servers with HT turned on.



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