linux-kernel - Re: [PATCH -tip 0/4] perf-probe updates: string support, etc.

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Date:	Mon, 5 Jul 2010 21:54:09 -0300
From:	Arnaldo Carvalho de Melo <acme@...radead.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Chase Douglas <chase.douglas@...onical.com>,
	Ingo Molnar <mingo@...e.hu>,
	lkml <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Mike Galbraith <efault@....de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	systemtap <systemtap@...rces.redhat.com>,
	DLE <dle-develop@...ts.sourceforge.net>
Subject: Re: [PATCH -tip 0/4] perf-probe updates: string support, etc.

Em Mon, Jul 05, 2010 at 02:44:50PM -0300, Arnaldo Carvalho de Melo escreveu:
> Em Mon, Jul 05, 2010 at 10:30:47AM -0400, Chase Douglas escreveu:
> > On May 19, 2010, at 3:57 PM, Masami Hiramatsu wrote:
> > > Here is a series of patches which improves perf probe to
> > > add below features. I cleared some coding style issues.

> > > - String support, which enables dynamic events to trace string
> > >  variables instead of its address.

> > > - Fixed-index array entry support, which allows user to trace
> > >  an array entry with digit index, e.g. array[0].

> > > - Global/static variable support, which allows user to trace
> > >  global or static variables, as same as local one.

> > What's the status of these patches? They seem very useful to me, but I
> > don't see them in Arnaldo's tree at git.kernel.org.

> Thanks for reminding me about these ones, will look at them to get them
> in perf/core.

Masami, I fixed up a minor conflict and while trying it this happened:

[root@...lia ~]# perf probe -a 'bio_split bi->bi_io_vec[0]'
kprobe_events file does not exist - please rebuild kernel with CONFIG_KPROBE_EVENT.
  Error: Failed to add events. (-1)

But on a second try:

[root@...lia ~]# l /sys/kernel/debug/tracing/kprobe_events 
-rw-r--r-- 1 root root 0 Jul  5 18:37 /sys/kernel/debug/tracing/kprobe_events
[root@...lia ~]# cat /sys/kernel/debug/tracing/kprobe_events 
[root@...lia ~]#
[root@...lia ~]# perf probe -a 'bio_split bi->bi_io_vec[0]'
Add new event:
  probe:bio_split      (on bio_split with bi_io_vec=bi->bi_io_vec[0])

You can now use it on all perf tools, such as:

	perf record -e probe:bio_split -aR sleep 1

[root@...lia ~]# cat /sys/kernel/debug/tracing/kprobe_events 
p:probe/bio_split bio_split bi_io_vec=+0(+72(%di)):u64
[root@...lia ~]# 

I'll push it as is, posting the pull request with the patches today,
please check if everything is ok and send fixups if needed,

Thanks,

- Arnaldo
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