[linux-audio-dev] gettimeofday() realtime safe?

[David Olofson]

On Thursday 21 April 2005 16.28, Lee Revell wrote:
[...]
> Yes, Linux implements gettimeofday via rdtsc() on x86.

...except on some x86 clones that don't have a working RDTSC 
implementation. Generally, all Pentium compatibles and higher should 
have it, but some don't.

Also, RDTSC is essentially useless on some early systems with core 
clock throttling. Finally, RDTSC sometimes means trouble on SMP 
systems, where the TSCs are not guaranteed to be synchronized. AFAIK, 
both of these issues have been dealt with in current generation CPUs 
and chipsets, but it might be a good idea to check...


> Which is why if you 
> can get away with just using rdtsc directly for timing it's better
> than gettimeofday.

Yeah. It's probably ok to just assume it's there if you're dealing 
with P3 generation intels and alternatives, but for maximum x86 
portability (non-intel CPUs and pre-Pentium CPUs), and portability 
beyond x86, one needs a fallback.


//David Olofson - Programmer, Composer, Open Source Advocate

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