linux-kernel - Re: [PATCH v2 1/4] perf probe: Generate event name with line number

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Date:   Tue, 12 Nov 2019 17:31:31 +0700
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-kernel@...r.kernel.org,
        Tom Zanussi <tom.zanussi@...ux.intel.com>,
        Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        Namhyung Kim <namhyung@...nel.org>
Subject: Re: [PATCH v2 1/4] perf probe: Generate event name with line number

Hi Arnaldo,

On Mon, 11 Nov 2019 11:07:33 -0300
Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> Em Mon, Nov 11, 2019 at 11:06:25AM -0300, Arnaldo Carvalho de Melo escreveu:
> > Em Mon, Nov 11, 2019 at 11:04:50AM -0300, Arnaldo Carvalho de Melo escreveu:
> > > Em Fri, Nov 08, 2019 at 01:27:58AM +0900, Masami Hiramatsu escreveu:
> > > > Generate event name from function name with line number
> > > > as <function>_L<line_number>. Note that this is only for
> > > > the new event which is defined by the line number of
> > > > function (except for line 0).
> > > > 
> > > > If there is another event on same line, you have to use
> > > > "-f" option. In that case, the new event has "_1" suffix.
> > > > 
> > > >  e.g.
> > > >   # perf probe -a kernel_read:1
> > > >   Added new events:
> > > >     probe:kernel_read_L1 (on kernel_read:1)
> > > 
> > > While testing this, using the same function (kernel_read), I found it
> > > confusing that it is possible to insert probes in lines seemingly with
> > > no code, for instance:
> > > 
> > > [root@...co ~]# perf probe -a kernel_read:1
> > > Added new event:
> > >   probe:kernel_read_L1 (on kernel_read:1)
> > > 
> > > You can now use it in all perf tools, such as:
> > > 
> > > 	perf record -e probe:kernel_read_L1 -aR sleep 1
> > > 
> > > [root@...co ~]# perf probe -a kernel_read:2
> > > Added new event:
> > >   probe:kernel_read_L2 (on kernel_read:2)
> > > 
> > > You can now use it in all perf tools, such as:
> > > 
> > > 	perf record -e probe:kernel_read_L2 -aR sleep 1
> > > 
> > > #
> > > # perf probe --list
> > >   probe:kernel_read_l1 (on kernel_read@...read_write.c)
> > >   probe:kernel_read_l2 (on kernel_read:1@...read_write.c)
> > 
> > 
> > Also look above at the listing, I would expect this instead:
> > 
> > # perf probe --list
> >   probe:kernel_read_l1 (on kernel_read:1@...read_write.c)
> >   probe:kernel_read_l2 (on kernel_read:2@...read_write.c)
> > 
> > Right?

Yes, it should be so.

> 
> And this one may be a problem with this specific patch, so I'll hold off
> processing this series till you have a chance to look at these problems
> and reply,

OK, let me check the reason why.

Thank you!

> 
> Thanks,
> 
> - Arnaldo


-- 
Masami Hiramatsu <mhiramat@...nel.org>