linux-kernel - Re: [PATCH 13/54] perf tools: Support perf event alias name

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Date:	Wed, 3 Feb 2016 21:35:55 -0200
From:	Arnaldo Carvalho de Melo <acme@...hat.com>
To:	Wang Nan <wangnan0@...wei.com>, Jiri Olsa <jolsa@...hat.com>
Cc:	Alexei Starovoitov <ast@...nel.org>,
	Brendan Gregg <brendan.d.gregg@...il.com>,
	Daniel Borkmann <daniel@...earbox.net>,
	"David S. Miller" <davem@...emloft.net>,
	He Kuang <hekuang@...wei.com>, Jiri Olsa <jolsa@...nel.org>,
	Li Zefan <lizefan@...wei.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>, pi3orama@....com,
	Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 13/54] perf tools: Support perf event alias name

Em Mon, Jan 25, 2016 at 09:56:00AM +0000, Wang Nan escreveu:
> From: He Kuang <hekuang@...wei.com>
> 
> This patch is useful when trying to pass a perf event to BPF map.
> Before this patch we are unable to pass an event with config term to
> BPF maps. For example:
> 
>  # perf record -a -e cycles/no-inherit,period=0x7fffffffffffffff/ \
>                   -e './test_bpf_map_2.c/maps:pmu_map.event=cycles/no-inherit,period=0x7fffffffffffffff//' ls /
>  event syntax error: '..ps:pmu_map.event=cycles/'
>                                    \___ Event not found for map setting
> 
> Because those '/' and ',' embarrass parser.
> 
> This patch adds new bison rules for specifying an alias name to a perf
> event, which allows cmdline refer to previous defined perf event through
> its name. With this patch user can give alias name to a perf event using
> following cmdline. The above goal can be achieved using:
> 
>  # perf record -a -e cyc=cycles/no-inherit,period=0x7fffffffffffffff/ \
>                   -e './test_bpf_map_2.c/maps:pmu_map.event=cyc/' ls /

In another thread Jiri suggested this as a way to get an alias
associated with some event:

 -----------------------------------------------------------------
On Tue, Feb 02, 2016 at 05:24:16PM +0100, Andreas Hollmann wrote:
> Jiri, how do you handle raw counters with this python stat__*
> callback? What is the name of the callback?

you can use 'name' term like:
  perf stat -e cycles,"cpu/config=0x6530160,name=krava/"

and use following callback in your script:
  def stat__krava(cpu, thread, time, val, ena, run):

 -----------------------------------------------------------------

Can't we go with that existing syntax? Jiri?

That would be:

  # perf record -a -e cycles/no-inherit,period=0x7fffffffffffffff,name=cyc/ \
                   -e './test_bpf_map_2.c/maps:pmu_map.event=cyc/' ls /

Your way is shorter, but we already have this name=foo method :-\

- Arnaldo