Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934105Ab2JXItN (ORCPT ); Wed, 24 Oct 2012 04:49:13 -0400 Received: from mail-lb0-f174.google.com ([209.85.217.174]:48473 "EHLO mail-lb0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933623Ab2JXItK (ORCPT ); Wed, 24 Oct 2012 04:49:10 -0400 MIME-Version: 1.0 In-Reply-To: <1351058350-9159-1-git-send-email-zheng.z.yan@intel.com> References: <1351058350-9159-1-git-send-email-zheng.z.yan@intel.com> Date: Wed, 24 Oct 2012 10:49:08 +0200 Message-ID: Subject: Re: [PATCH V2 0/7] perf, x86: Haswell LBR call stack support From: Stephane Eranian To: "Yan, Zheng" Cc: LKML , Peter Zijlstra , "ak@linux.intel.com" Content-Type: text/plain; charset=UTF-8 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1512 Lines: 33 On Wed, Oct 24, 2012 at 7:59 AM, Yan, Zheng wrote: > From: "Yan, Zheng" > > Haswell has a new feature that utilizes the existing Last Branch Record > facility to record call chains. When the feature is enabled, function > call will be collected as normal, but as return instructions are executed > the last captured branch record is popped from the on-chip LBR registers. > The LBR call stack facility can help perf to get call chains of progam > without frame pointer. > > The LBR call stack has following known limitations > 1. Zero length calls are not filtered out by hardware > 2. Exception handing such as setjmp/longjmp will have calls/returns not > match > 3. Pushing different return address onto the stack will have calls/returns > not match > > The patch series depends on Andi's "perf PMU support for Haswel" patches > The part that is missing here is that you don't explain that you are now fitting LBR cstack under PERF_SAMPLE_CALLCHAIN. It is dynamically enabled based on users callstack request mode. > --- > Changes since v1 > - not expose PERF_SAMPLE_BRANCH_CALL_STACK to user space > - save/restore LBR stack on context switch for all sampling branch modes > - reduce lbr_sel_map size -- 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/