linux-kernel - Re: [patch v3] perf tools: perf list broken on ARM

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Date:	Mon, 16 Dec 2013 14:14:39 +0900
From:	Namhyung Kim <namhyung@...nel.org>
To:	Vince Weaver <vincent.weaver@...ne.edu>
Cc:	linux-kernel@...r.kernel.org,
	Chad Paradis <chad.paradis@...t.maine.edu>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>, Jiri Olsa <jolsa@...hat.com>,
	Paul Mackerras <paulus@...ba.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [patch v3] perf tools: perf list broken on ARM

Hi Vince,

On Sat, 14 Dec 2013 15:25:18 -0500 (EST), Vince Weaver wrote:
> OK, here's an updated version that reuses evsel and hopefully doesn't leak 
> memory like the previous patch I posted.
>
>
> "perf list" listing of hardware events doesn't work on older ARM devices.
> The change enabling event detection:
>
>  commit b41f1cec91c37eeea6fdb15effbfa24ea0a5536b
>  Author: Namhyung Kim <namhyung.kim@....com>
>  Date:   Tue Aug 27 11:41:53 2013 +0900
>
>      perf list: Skip unsupported events
>
>
> uses the following code in tools/perf/util/parse-events.c:
>
>         struct perf_event_attr attr = {
>                 .type = type,
>                 .config = config,
>                 .disabled = 1,
>                 .exclude_kernel = 1,
>         };
>
> On ARM machines pre-dating the Cortex-A15 this doesn't work, as
> these machines don't support .exclude_kernel.  So starting with 3.12
> "perf list" does not report any hardware events at all on older
> machines (seen on Rasp-Pi, Pandaboard, Beagleboard, etc).
>
> This version of the patch makes changes suggested by Namhyung Kim
> to check for EACCESS and retry (instead of just dropping
> the exclude_kernel) so we can properly handle machines where 
> /proc/sys/kernel/perf_event_paranoid is set to 2.
>
> Reported-by: Chad Paradis <chad.paradis@...t.maine.edu>
> Signed-off-by: Vince Weaver <vincent.weaver@...ne.edu>

Acked-by: Namhyung Kim <namhyung@...nel.org>

Thanks,
Namhyung
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