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Re: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf probe and kprobe-tracer bugfixes
- From: Masami Hiramatsu <mhiramat at redhat dot com>
- To: Ingo Molnar <mingo at elte dot hu>
- Cc: Frederic Weisbecker <fweisbec at gmail dot com>, Steven Rostedt <rostedt at goodmis dot org>, lkml <linux-kernel at vger dot kernel dot org>, Thomas Gleixner <tglx at linutronix dot de>, Arnaldo Carvalho de Melo <acme at redhat dot com>, Mike Galbraith <efault at gmx dot de>, Paul Mackerras <paulus at samba dot org>, Peter Zijlstra <a dot p dot zijlstra at chello dot nl>, Christoph Hellwig <hch at infradead dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Jim Keniston <jkenisto at us dot ibm dot com>, "Frank Ch. Eigler" <fche at redhat dot com>, "H. Peter Anvin" <hpa at zytor dot com>, systemtap <systemtap at sources dot redhat dot com>, DLE <dle-develop at lists dot sourceforge dot net>
- Date: Mon, 19 Oct 2009 18:54:19 -0400
- Subject: Re: [PATCH -tip tracing/kprobes 0/9] tracing/kprobes, perf: perf probe and kprobe-tracer bugfixes
- References: <20091017000711.16556.69935.stgit@dhcp-100-2-132.bos.redhat.com> <20091017080203.GA4155@elte.hu> <20091017103427.GA31238@elte.hu> <4ADAAF50.9040604@redhat.com> <20091019075103.GF17960@elte.hu> <20091019110055.GA5549@nowhere> <20091019112125.GA12829@elte.hu> <4ADCC348.2020800@redhat.com>
Masami Hiramatsu wrote:
> Ingo Molnar wrote:
>> For example you might want to probe the point within schedule that calls
>> switch_mm() - this could be done via:
>>
>> perf probe schedule@switch_mm
>>
>> Or the point where 'next' gets assigned? Sure, you dont need to even
>> open the editor, if you know the rough outline of the function you can
>> probe it via:
>>
>> perf probe schedule@'next ='
>>
>> Note that i was able to specify both probes without having opened an
>> editor - just based on the general knowledge of the scheduler.
>
> It may be useful for return probe too :-)
>
> perf probe schedule@return
Hmm, IMHO,
>> perf probe schedule@switch_mm
might be confused as 'probe schedule() called from switch_mm()'.
BTW, there might be several local/inline functions which have
same name.
I think we'd better provide a syntax for solving this issue.
And current syntax uses @ for this purpose as below.
perf probe localfunc@file
Maybe, we still can use % for special matching,
perf probe schedule%switch_mm
These can be combined with each other, as below.
perf probe schedule@kernel/sched.c%switch_mm
Or, supporting lazy string pattern matching
(reusing glob matching in ftrace?)
perf probe schedule:'switch_mm(*);'
Just my thought.
Thank you,
--
Masami Hiramatsu
Software Engineer
Hitachi Computer Products (America), Inc.
Software Solutions Division
e-mail: mhiramat@redhat.com