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From: Andy Lutomirski <luto@amacapital.net>
To: Andi Kleen <andi@firstfloor.org>
Cc: Stephane Eranian <eranian@google.com>,
	"Yan, Zheng" <zheng.z.yan@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Ingo Molnar <mingo@kernel.org>,
	Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support
Date: Wed, 26 Feb 2014 10:59:17 -0800	[thread overview]
Message-ID: <CALCETrVQ8SBg+YLuPmDevL+f2dzBjLJucfMvVHaB04E8QJSGXw@mail.gmail.com> (raw)
In-Reply-To: <20140226185513.GL22728@two.firstfloor.org>

On Wed, Feb 26, 2014 at 10:55 AM, Andi Kleen <andi@firstfloor.org> wrote:
>> I'm suggesting a perf event option, just like the way that PEBS works.
>
> Right now it's a somewhat experimental feature and just having
> the sysctl is fine. If it turns out that is what everyone uses
> such an option could be still added later.

I'm a bit worried that the syscall will be stuck as ABI forever,
though.  Its presence will make adding a different configuration
mechanism awkward.

>
> I suspect most people would still use FP if they can, just use
> the LBRs if that doesn't work.

I wonder if anyone who uses perf for userspace profiling *ever* uses
FP and gets away with it.  There's precious little userspace software
compiled with frame pointers these days on most architectures.

I have a concrete reason for this question: it would be nice to
compile the vDSO with frame pointers off.  IIRC there would be a
significant performance gain, and I think the only thing that would
break is perf.  But it looks like perf will have nice elfutils unwind
support in 3.15, and if FP support is useless anyway...

--Andy

  reply	other threads:[~2014-02-26 18:59 UTC|newest]

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-18  6:07 [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 01/14] perf, x86: Reduce lbr_sel_map size Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 02/14] perf, core: introduce pmu context switch callback Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 03/14] perf, x86: use context switch callback to flush LBR stack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 04/14] perf, x86: Basic Haswell LBR call stack support Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 05/14] perf, core: pmu specific data for perf task context Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 06/14] perf, core: always switch pmu specific data during context switch Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 07/14] perf, x86: track number of events that use LBR callstack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 08/14] perf, x86: allocate space for storing LBR stack Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 09/14] perf, x86: Save/resotre LBR stack during context switch Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 10/14] perf, core: simplify need branch stack check Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 11/14] perf, core: Pass perf_sample_data to perf_callchain() Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 12/14] perf, x86: use LBR call stack to get user callchain Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 13/14] perf, x86: enable LBR callstack when recording callchain Yan, Zheng
2014-02-18  6:07 ` [PATCH v3 14/14] perf, x86: Discard zero length call entries in LBR call stack Yan, Zheng
2014-02-23 19:47 ` [PATCH v3 00/14] perf, x86: Haswell LBR call stack support Stephane Eranian
2014-02-24  1:07   ` Yan, Zheng
2014-02-24  7:14 ` Peter Zijlstra
2014-02-26  2:39 ` Andy Lutomirski
2014-02-26  7:04   ` Stephane Eranian
2014-02-26  8:57     ` Yan, Zheng
2014-02-26 16:03     ` Andy Lutomirski
2014-02-26 18:55       ` Andi Kleen
2014-02-26 18:59         ` Andy Lutomirski [this message]
2014-02-26 19:19           ` David Ahern
2014-02-26 19:25             ` Andy Lutomirski
2014-02-26 20:14               ` David Ahern
2014-02-26 20:26                 ` Andy Lutomirski
2014-04-09 11:48                   ` Peter Zijlstra
2014-04-09 16:48                     ` Andi Kleen
2014-04-09 17:40                       ` Andi Kleen
2014-02-26 20:32                 ` Peter Zijlstra
2014-02-26 20:53                 ` Andi Kleen
2014-02-26 21:15                   ` Peter Zijlstra
2014-02-26 21:33                     ` Andi Kleen
2014-02-26 21:34                   ` David Ahern
2014-02-26 21:42                     ` Andi Kleen
2014-02-27  9:09                       ` Stephane Eranian
2014-02-27 12:35           ` Ingo Molnar
2014-02-27 16:08             ` Andi Kleen

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