linux-kernel - Re: [PATCH -tip 0/9] perf-probe updates

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Message-ID: <4B16E1C0.7000401@redhat.com>
Date:	Wed, 02 Dec 2009 16:53:04 -0500
From:	Masami Hiramatsu <mhiramat@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
CC:	Frederic Weisbecker <fweisbec@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Jim Keniston <jkenisto@...ibm.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Christoph Hellwig <hch@...radead.org>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	Jason Baron <jbaron@...hat.com>,
	"K.Prasad" <prasad@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...hat.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [PATCH -tip 0/9] perf-probe updates

Ingo Molnar wrote:
>
> * Masami Hiramatsu<mhiramat@...hat.com>  wrote:
>
>> Hi,
>>
>> Here are bugfixes and updates for perf-probe and kprobe-tracer. I've
>> fixed some minor bugs and added --list option and simple probe naming.
>
> Applied, thanks Masami!
>
>> TODO:
>>   - Support build-id checking.
>>   - Support --del option to remove probes.
>>   - Support --line option to show which lines user can probe.
>>   - Support lazy string matching.
>
> ok, cool!
>
> One other small detail i noticed wrt. probe naming. Right now if we
> insert a single probe into a function it gets named schedule_0:
>
>   # perf probe schedule
>   Could not open vmlinux/module file. Try to use symbols.
>   Added new event: p:probe/schedule_0 schedule+0
>
> the next one gets named schedule_1, schedule_2, etc.
>
> It would be nice to special-case the first one and name it 'schedule'.
> Most of the time people insert a single probe into a function, so the _0
> postfix is extra and in most cases unnecessary typing for them.

Sure, that's reasonable.

>
> Another small detail is that i dont think we should emit this line:
>
>   Could not open vmlinux/module file. Try to use symbols.
>
> when we can create a probe successfully - it's just unnecessary noise,
> the user does not care how we pulled it off, as long as we were able to
> get a reliable symbol address and the insertion worked fine.

OK, I'll make it a debug message.

> A third detail is this line:
>
>   Added new event: p:probe/schedule_0 schedule+0
>
> If that is pasted to perf stat directly it wont work because the syntax
> is probe:schedule_0. So i'd suggest to print something like:
>
>   Added new event: probe/schedule_0 (on schedule+0)

Sure, perf always use ':' for event group separator, so

Added new event: probe:schedule (on schedule+0 [with ...(args)])

>
> Perhaps even print another line:
>
>    You can now use it on all perf tools, such as:
>
>      perf probe -e probe/schedule_0 -a sleep 1
>      perf record -e probe/schedule_0 -a sleep 1

OK.

Thank you for good advice!

>
> ... to show people how to make use of it.
>
> Thanks,
>
> 	Ingo

-- 
Masami Hiramatsu

Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division

e-mail: mhiramat@...hat.com

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