Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:

From: Ingo Molnar
Date: Mon Oct 28 2013 - 06:34:11 EST

* Pekka Enberg <penberg@xxxxxx> wrote:

> On 10/26/2013 02:16 PM, Frank Ch. Eigler wrote:
> >Pekka Enberg <penberg@xxxxxxxxxx> writes:
> >
> >>Is there a technical reason why 'perf list' could not show all the
> >>available SDT markers on a system and that the 'mark to event'
> >>mapping cannot happen automatically? [...]
> >A quick experiment with:
> >
> > find `echo $PATH | tr : ' '` -type f -perm -555 |
> > xargs readelf -n 2>/dev/null |
> > grep STAP 2>/dev/null
> >
> >suggests reasonable performance for my F19 workstation (a second or
> >two over ~6000 executables), once all the ELF content is in the block
> >cache. According to a stap eventcount.stp run, that required about
> >50000 events.
> >
> >Note that a $PATH search excludes shared libraries, which can also
> >carry <sys/sdt.h> markers. Adding /usr/lib* in more than doubles the
> >work, then there's /usr/libexec etc.
> Thanks for providing numbers to the discussion. AFAICT, we might
> even be able to just scan everything for 'perf list' by default.

That should definitely be better in the long run than any whitelist
(or no list at all).


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