Date: Tue, 15 Dec 2015 14:18:34 +0100
From: Jiri Olsa <jolsa@redhat.com>
To: Wang Nan <wangnan0@huawei.com>
Cc: acme@kernel.org, masami.hiramatsu.pt@hitachi.com, jolsa@kernel.org,
        linux-kernel@vger.kernel.org, pi3orama@163.com, lizefan@huawei.com,
        He Kuang <hekuang@huawei.com>, Alexei Starovoitov <ast@kernel.org>,
        Arnaldo Carvalho de Melo <acme@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>
Subject: Re: [PATCH v5 08/14] perf tools: Support perf event alias name
Message-ID: <20151215131834.GB31734@krava.brq.redhat.com>
References: <1450089563-122430-1-git-send-email-wangnan0@huawei.com>
 <1450089563-122430-9-git-send-email-wangnan0@huawei.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1450089563-122430-9-git-send-email-wangnan0@huawei.com>
User-Agent: Mutt/1.5.24 (2015-08-30)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2002
Lines: 55

On Mon, Dec 14, 2015 at 10:39:17AM +0000, Wang Nan wrote:
> From: He Kuang <hekuang@huawei.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.

we already have 'name=' term, but it's only for pmu events,
so I think your solution is better

> 
> 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 /
> 

so this alias should only help as a quick pointer
to setup the record session, right?

I'm not sure we want to see it as a part of name being stored
to perf.data and displayed by perf report and stat

  $ ./perf stat -e cyc=cycles ls

    Performance counter stats for 'ls':

         2,638,646      cyc=cycles                                                  

       0.001111614 seconds time elapsed

but I guess when you probably have a reason to use that
you want to see it in your report..  just a thought ;-)

anyway acking the change

Acked-by: Jiri Olsa <jolsa@kernel.org>

thanks,
jirka
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/