From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <ak@linux.intel.com>
Cc: kan.liang@intel.com, linux-kernel@vger.kernel.org,
mingo@redhat.com, acme@kernel.org
Subject: Re: [RFC PATCH 1/1] proc: introduce /proc/<pid>/lbr_stack
Date: Fri, 27 Feb 2015 08:58:29 +0100 [thread overview]
Message-ID: <20150227075829.GC21418@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20150223174448.GE27767@tassilo.jf.intel.com>
On Mon, Feb 23, 2015 at 09:44:48AM -0800, Andi Kleen wrote:
> On Mon, Feb 23, 2015 at 05:49:57PM +0100, Peter Zijlstra wrote:
> > On Mon, Feb 23, 2015 at 03:43:41AM +0000, kan.liang@intel.com wrote:
> > > From: Kan Liang <kan.liang@intel.com>
> > >
> > > Haswell has a new feature that utilizes the existing Last Branch Record
> > > facility to record call chains. It has been implemented in perf. The
> > > call chains information is saved during perf event context.
> > >
> > > This patch exposes a /proc/<pid>/lbr_stack file that shows the saved LBR
> > > call chain information.
> >
> > But why? I mean, this thing is only useful if you have a concurrently
> > running perf record that selects the LBR-stack stuff.
> >
> > And if you have that, you might as well look at its output instead. Why
> > add this unconditional proc file that doesn't function on its own?
>
> perf record doesn't show where you're currently blocked.
Of course it does; look at perf inject -s.
http://article.gmane.org/gmane.linux.kernel/1225774
http://article.gmane.org/gmane.linux.kernel/1225775
next prev parent reply other threads:[~2015-02-27 7:58 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-23 3:43 [RFC PATCH 1/1] proc: introduce /proc/<pid>/lbr_stack kan.liang
2015-02-23 16:49 ` Peter Zijlstra
2015-02-23 17:44 ` Andi Kleen
2015-02-27 7:58 ` Peter Zijlstra [this message]
2015-02-27 17:54 ` Andi Kleen
2015-02-27 22:05 ` Peter Zijlstra
2015-02-27 23:57 ` Andi Kleen
2015-02-28 10:18 ` Peter Zijlstra
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