Re: performance counter ~0.4% error finding retired instructioncount

[Ingo Molnar]

* Paul Mackerras <paulus@xxxxxxxxx> 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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