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SubjectRe: performance counter ~0.4% error finding retired instruction count

* Paul Mackerras <paulus@samba.org> wrote:

> Ingo Molnar writes:
>
> > I measured 2000, but generally a few thousand cycles per
> > invocation sounds about right.
>
> We could actually do a bit better than we do, fairly easily. We
> could attach the counters to the child after the fork instead of
> the parent before the fork, using a couple of pipes for
> synchronization. And there's probably a way to get the dynamic
> linker to resolve the execvp call early in the child so we avoid
> that overhead. I think we should be able to get the overhead down
> to tens of userspace instructions without doing anything
> unnatural.

Definitely so.

Ingo


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