Re: PThread profiling

[Mark Wielaard <mjw at redhat dot com>]

Hi Daniel,

On Wed, 2009-02-25 at 12:08 +0100, Daniel Tralamazza wrote:
> I was surprised with the low performance of static markers so did some
> oprofiling. Good news (as expected), there is no difference between
> the original glibc and the one with markers added.

I assume when you say "original glibc" you mean, run with dynamic
markers added instead of static markers?

> Here are some results http://pastebin.com/ffcf4cc3 for static markers
> (sunspider benchmark on firefox). Over 1/3 of all samples comes from
> traps (traps_64.c:71), I didn't know that even static markers use
> int3.
> Sunspider results for static markers http://tinyurl.com/bsjrof
> And baseline http://tinyurl.com/ct4pwm

It seems the slowdown is terrible on the string tests. Any idea what
they do that they seem to hit the pthread probes so much? Or do they hit
a probe with a really high overhead?

Might it be a somewhat unfortunately placed marker that is really hit a
lot of times in this particular case? Maybe you can try running with
stap -t to get some rough statistic on how many times and with how much
overhead each probe is being hit?

Thanks,

Mark