Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754710AbbB0H6l (ORCPT ); Fri, 27 Feb 2015 02:58:41 -0500 Received: from casper.infradead.org ([85.118.1.10]:33351 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750889AbbB0H6j (ORCPT ); Fri, 27 Feb 2015 02:58:39 -0500 Date: Fri, 27 Feb 2015 08:58:29 +0100 From: Peter Zijlstra To: Andi Kleen 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//lbr_stack Message-ID: <20150227075829.GC21418@twins.programming.kicks-ass.net> References: <1424663021-82663-1-git-send-email-kan.liang@intel.com> <20150223164957.GB5029@twins.programming.kicks-ass.net> <20150223174448.GE27767@tassilo.jf.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150223174448.GE27767@tassilo.jf.intel.com> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1334 Lines: 29 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 > > > > > > 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//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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/