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Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- From: fche at redhat dot com (Frank Ch. Eigler)
- To: Pekka Enberg <penberg at kernel dot org>
- Cc: 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: Sat, 26 Oct 2013 07:16:05 -0400
- 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>
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.
- FChE