Re: Semaphore assembly-code bug

[Chris Friesen]

Linus Torvalds wrote:

> On Intel, if I recall correctly, rdtsc is totally serializing, so you're
> testing not just the instructions between the rdtsc's, but the length of
> the pipeline, and the time it takes for stuff around it to calm down.  

Actually, the Intel docs say that rdtsc is not serializing (specifically for the 
P6 series, but linked off the P4 section of the site) and their sample 
performance measuring code for the P4 shows it using a serializing instruction 
before the call to rdtsc.

Chris
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