linux-kernel - Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support

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Date:	Wed, 26 Feb 2014 16:57:02 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	Stephane Eranian <eranian@...gle.com>,
	Andy Lutomirski <luto@...capital.net>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support

On 02/26/2014 03:04 PM, Stephane Eranian wrote:
> On Wed, Feb 26, 2014 at 3:39 AM, Andy Lutomirski <luto@...capital.net> wrote:
>> On 02/17/2014 10:07 PM, Yan, Zheng wrote:
>>>
>>> This patch series adds LBR call stack support. User can enabled/disable
>>> this through an sysfs attribute file in the CPU PMU directory:
>>>  echo 1 > /sys/bus/event_source/devices/cpu/lbr_callstack
>>
>> This seems like an unpleasant way to control this.  It would be handy to
>> be able to control this as an option to perf record.
>>
> That would mean you'd be root for perf.
> Or are you suggesting a perf event option? But then, you'd expose arch-specific
> feature at the API level.
> 

Another option is enable this feature by default if hardware supports it. But it
causes LBR contention between events that want callstack and evnets that want LBR.

Regards
Yan, Zheng
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