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Date: Thu, 27 Feb 2014 13:35:07 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Andy Lutomirski <luto@amacapital.net>
Cc: Andi Kleen <andi@firstfloor.org>, 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>,
        Arnaldo Carvalho de Melo <acme@infradead.org>
Subject: Re: [PATCH v3 00/14] perf, x86: Haswell LBR call stack support
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* Andy Lutomirski <luto@amacapital.net> wrote:

> 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. [...]

NACKed-by: Ingo Molnar <mingo@kernel.org>

> > [...] 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.

The sysctl is a usability non-starter, obviously.

Thanks,

	Ingo