Re: Hyper-Threading Vulnerability

[dean gaudet <dean-list-linux-kernel@arctic.org>]

On Sat, 14 May 2005, Arjan van de Ven wrote:

> it's a matter of time (my estimate is a year or two) before processors
> get variable frequencies based on temperature targets etc...
> and then rdtsc is really useless for this kind of thing..

what do you mean "a year or two"?  processors have been doing this for 
many years now.

i'm biased, but i still think transmeta did this the right way... the tsc 
operates at the top frequency of the processor always.

i do a hell of a lot of microbenchmarking on various processors and i 
always use tsc -- but i'm just smart enough to take multiple samples and i 
try to make each sample smaller than a time slice... which avoids most of 
the pitfalls, and would even work on smp boxes with tsc differences.

-dean
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