linux-kernel - Re: [PATCH 3/3] perf, tool: Add new event group management

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Date:	Tue, 20 Mar 2012 23:36:36 +0100
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	acme@...hat.com, mingo@...e.hu, paulus@...ba.org,
	cjashfor@...ux.vnet.ibm.com, fweisbec@...il.com,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 3/3] perf, tool: Add new event group management

On Tue, Mar 20, 2012 at 07:44:41PM +0100, Peter Zijlstra wrote:
> On Tue, 2012-03-20 at 19:15 +0100, Jiri Olsa wrote:
> > Examples (first event in brackets is group leader):
> > 
> >   # 1 group (cpu-clock,task-clock)
> >   perf record --group -e cpu-clock,task-clock ls
> >   perf record --group parsed -e cpu-clock,task-clock ls
> > 
> >   # 2 groups (cpu-clock,task-clock) (minor-faults,major-faults)
> >   perf record --group parsed -e cpu-clock,task-clock \
> >    -e minor-faults,major-faults ls
> > 
> >   # 1 group (cpu-clock,task-clock,minor-faults,major-faults)
> >   perf record --group -e cpu-clock,task-clock \
> >    -e minor-faults,major-faults ls
> > 
> >   # 2 groups (cpu-clock,task-clock) (minor-faults,major-faults)
> >   perf record --group parsed -e cpu-clock,task-clock \
> >    -e minor-faults,major-faults -e instructions ls
> > 
> >   # 1 group (cpu-clock,task-clock,minor-faults,major-faults,instructions)
> >   perf record --group -e cpu-clock,task-clock \
> >    -e minor-faults,major-faults -e instructions ls 
> 
> I can't help but dislike the --group/--group parsed thing...
> 
> How about something like:
> 
>   event_group = "{", events, "}" , [ ":", event_group_mod ]
> 
> Such that you can write things like:
> 
>   perf record -e "{cpu-clock,cache-misses,cache-references}"
> 
>   perf stat -e "{cpu-clock,cycles},{cpu-clock,cache-misses,cache-references}"
>   perf stat -e "{cpu-clock,cycles}" -e "{cpu-clock,cache-misses,cache-references}"

there should be no problem with that

> 
> I'm not sure what the current behaviour of --group is, if you create a
> group like this, do they all sample?

I think so.. the --group switch just set the group_fd for the event syscall, nothing else

> 
> If so, we need some option like:
> 
>   perf record -e "{cpu-clock,cache-misses,cache-references}:1"
> 
> to mean, only sample on cpu-clock but use PERF_SAMPLE_READ and
> PERF_FORMAT_GROUP to read all siblings on every cpu-clock sample.

never happy, are you.. ;) seems like nice feature, will check

> 
> Now the disadvantage is that {} needs quotes on bash, the advantage is
> that its completely natural on how to construct groups, without weird
> --group/--group parsed. Also it provides a place for group modifiers.

looks like Arnaldo could use [] but I get different results:

[jolsa@...p-26-214 perf]$ ./perf stat -e [cycles,instructions] ls
invalid or unsupported event: 't'

need to check.. maybe escaping is small price for good readability,
but I'll think about some other way as well.

thanks for comments,
jirka
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