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From: Namhyung Kim <namhyung@kernel.org>
To: kan.liang@intel.com
Cc: acme@kernel.org, jolsa@redhat.com, a.p.zijlstra@chello.nl,
	eranian@google.com, linux-kernel@vger.kernel.org,
	mingo@redhat.com, paulus@samba.org, ak@linux.intel.com
Subject: Re: [PATCH V3 1/3] perf tools: enable LBR call stack support
Date: Tue, 18 Nov 2014 14:54:48 +0900	[thread overview]
Message-ID: <87ppclqcif.fsf@sejong.aot.lge.com> (raw)
In-Reply-To: <1415972652-17310-2-git-send-email-kan.liang@intel.com> (kan liang's message of "Fri, 14 Nov 2014 08:44:10 -0500")

On Fri, 14 Nov 2014 08:44:10 -0500, kan liang wrote:
> From: Kan Liang <kan.liang@intel.com>
>
> Currently, there are two call chain recording options, fp and dwarf.
> Haswell has a new feature that utilizes the existing LBR facility to
> record call chains. So it provides the third options to record call
> chain. This patch enables the lbr call stack support.
>
> LBR call stack has some limitations. It reuses current LBR facility, so
> LBR call stack and branch record can not be enabled at the same time. It
> is only available for user callchain.
> However, LBR call stack can work on the user app which doesn't have
> frame-pointer or dwarf debug info compiled. It is a good alternative
> when nothing else works.

So this is only for Haswell or later, right?  What if user gives it to
the other CPUs - is it fail or ignore silently?  I think we need to warn
user about it more kindly..

Thanks,
Namhyung

  reply	other threads:[~2014-11-18  5:54 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-11-14 13:44 [PATCH V3 0/3] perf tool: Haswell LBR call stack support (user) kan.liang
2014-11-14 13:44 ` [PATCH V3 1/3] perf tools: enable LBR call stack support kan.liang
2014-11-18  5:54   ` Namhyung Kim [this message]
2014-11-18 13:57     ` Liang, Kan
2014-11-14 13:44 ` [PATCH V3 2/3] perf tool: Move cpumode resolve code to add_callchain_ip kan.liang
2014-11-17 13:57   ` Jiri Olsa
2014-11-17 14:00   ` Jiri Olsa
2014-11-18  8:24   ` Jiri Olsa
2014-11-21 15:06     ` Liang, Kan
2014-11-21 15:19       ` Arnaldo Carvalho de Melo
2014-11-14 13:44 ` [PATCH V3 3/3] perf tools: Construct LBR call chain kan.liang
2014-11-17 15:54   ` Jiri Olsa
2014-11-17 17:41     ` Liang, Kan
2014-11-18  6:13       ` Namhyung Kim
2014-11-18  7:55         ` Jiri Olsa
2014-11-18 14:37           ` Liang, Kan
2014-11-18 19:40             ` Liang, Kan
2014-11-19  5:57               ` Namhyung Kim
2014-11-17 15:55   ` Jiri Olsa
2014-11-18  6:14     ` Namhyung Kim
2014-11-18  6:25   ` Namhyung Kim
2014-11-18 14:01     ` Liang, Kan
2014-11-19  6:01       ` Namhyung Kim
2014-11-19 13:37         ` Liang, Kan
2014-11-17 16:01 ` [PATCH V3 0/3] perf tool: Haswell LBR call stack support (user) Jiri Olsa

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