The sixty second pmc howto

Robert Watson rwatson at FreeBSD.org
Thu Feb 23 07:32:08 PST 2006


On Thu, 23 Feb 2006, Andrew Gallatin wrote:

> Robert Watson writes:
>
> > (2) Run "pmcstat -S instructions -O /tmp/sample.out" to start sampling of
> >      instruction retirement events, saving the results to /tmp/sample.out.
>
> Dumb question, but what does "instructions" really mean?  The number of 
> instructions, the time spent executing them, ?

pmcstat magically translates 'instructions' into 'p4-instr-retired', which 
might well refer to what happens to an instruction when it is believed to have 
successfully executed.  Presumably this happens once you know it hasn't been 
mispredicted, etc, but I'm sure someone can give a better and more detailed 
answer.

Robert N M Watson


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