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Date: Fri, 27 Feb 2015 08:58:29 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Andi Kleen <ak@...ux.intel.com> Cc: kan.liang@...el.com, linux-kernel@...r.kernel.org, mingo@...hat.com, acme@...nel.org Subject: Re: [RFC PATCH 1/1] proc: introduce /proc/<pid>/lbr_stack 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@...el.com wrote: > > > From: Kan Liang <kan.liang@...el.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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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