Re: [RFC PATCH 1/1] proc: introduce /proc/<pid>/lbr_stack

From: Andi Kleen
Date: Mon Feb 23 2015 - 12:44:54 EST

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@xxxxxxxxx wrote:
> > From: Kan Liang <kan.liang@xxxxxxxxx>
> >
> > 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.


ak@xxxxxxxxxxxxxxx -- Speaking for myself only
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