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Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- From: Ingo Molnar <mingo at kernel dot org>
- To: Pekka Enberg <penberg at iki dot fi>
- Cc: "Frank Ch. Eigler" <fche at redhat dot com>, Pekka Enberg <penberg at kernel dot org>, Hemant Kumar <hkshaw at linux dot vnet dot ibm dot com>, LKML <linux-kernel at vger dot kernel dot org>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>, Peter Zijlstra <peterz at infradead dot org>, Oleg Nesterov <oleg at redhat dot com>, hegdevasant at linux dot vnet dot ibm dot com, Ingo Molnar <mingo at redhat dot com>, anton at redhat dot com, systemtap at sourceware dot org, Namhyung Kim <namhyung at kernel dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, aravinda at linux dot vnet dot ibm dot com
- Date: Mon, 28 Oct 2013 11:34:02 +0100
- Subject: Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- Authentication-results: sourceware.org; auth=none
- References: <20131023044511 dot 1886 dot 82571 dot stgit at hemant-fedora> <20131023050502 dot 1886 dot 15779 dot stgit at hemant-fedora> <CAOJsxLFKm3TxeTmGjbpr1r4sZ8fHcM481-5BM_Cq0J8hhtvBqQ at mail dot gmail dot com> <y0mbo2cs2oa dot fsf at fche dot csb> <526E2304 dot 1000407 at iki dot fi>
* Pekka Enberg <penberg@iki.fi> wrote:
> On 10/26/2013 02:16 PM, Frank Ch. Eigler wrote:
> >Pekka Enberg <penberg@kernel.org> 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 syscall.read 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).
Thanks,
Ingo