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Re: [PATCH v4 2/3] Support for perf to probe into SDT markers:
- From: Pekka Enberg <penberg at iki dot fi>
- To: Ingo Molnar <mingo at kernel dot org>, Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Hemant Kumar <hkshaw at linux dot vnet dot ibm dot com>, LKML <linux-kernel at vger dot kernel dot org>, 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 10:56:04 +0200
- 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> <20131025125921 dot GA29424 at linux dot vnet dot ibm dot com> <20131026095023 dot GF14237 at gmail dot com>
On 10/26/2013 12:50 PM, Ingo Molnar wrote:
I think in 99% of the usecases people will either use pre-built
markers that come with their distro, or will be intimately aware of
the markers because they are in the very app they are developing.
So I wouldn't worry about 'user has a weird binary' case too much.
I agree with Pekka that making them easily discoverable and visible
as a coherent whole is really important.
I wouldn't worry about the weird binary case either.
Even a build-time whitelist would help. Just put libc and libjvm
there and you're already covering a lot of interesting cases.
And if you then add a printout:
Use 'perf list --scan' to find more tracepoints on your
system.
you're now effectively covering 100% of the cases.
The trick of making the UI not suck is not to force the user
to think about the different mechanisms like SDT markers,
uprobes, or ktap scripts but to make them as transparent
as possible, provide useful defaults, and actively guide the
user towards learning about more command line options
for the complex cases.
Pekka