From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD504ECDFD0 for ; Fri, 14 Sep 2018 14:57:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79FDE20861 for ; Fri, 14 Sep 2018 14:57:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 79FDE20861 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728323AbeINUM1 (ORCPT ); Fri, 14 Sep 2018 16:12:27 -0400 Received: from mga03.intel.com ([134.134.136.65]:47909 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727838AbeINUM1 (ORCPT ); Fri, 14 Sep 2018 16:12:27 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 14 Sep 2018 07:57:33 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,373,1531810800"; d="scan'208";a="90494483" Received: from linux.intel.com ([10.54.29.200]) by orsmga001.jf.intel.com with ESMTP; 14 Sep 2018 07:57:33 -0700 Received: from [10.251.9.37] (kliang2-mobl1.ccr.corp.intel.com [10.251.9.37]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by linux.intel.com (Postfix) with ESMTPS id 7217058053F; Fri, 14 Sep 2018 07:57:32 -0700 (PDT) Subject: Re: [PATCH] perf/x86/intel/lbr: Optimize context switches for LBR To: Andi Kleen Cc: Alexey Budankov , linux-kernel-owner@vger.kernel.org, peterz@infradead.org, tglx@linutronix.de, acme@kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, jolsa@redhat.com, namhyung@kernel.org References: <1536869331-63561-1-git-send-email-kan.liang@linux.intel.com> <20180914085409.GA27886@tassilo.jf.intel.com> <529b2498-0515-e33c-ebcc-af2a5ca7d974@linux.intel.com> <20180914142733.GB27886@tassilo.jf.intel.com> From: "Liang, Kan" Message-ID: Date: Fri, 14 Sep 2018 10:57:31 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180914142733.GB27886@tassilo.jf.intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/14/2018 10:27 AM, Andi Kleen wrote: > On Fri, Sep 14, 2018 at 08:39:36AM -0400, Liang, Kan wrote: >> >> >> On 9/14/2018 5:22 AM, Alexey Budankov wrote: >>> >>> Hi Andi, >>> >>> On 14.09.2018 11:54, Andi Kleen wrote: >>>>>> In principle the LBRs need to be flushed between threads. So does >>>>>> current code. >>>>> >>>>> IMHO, ideally, LBRs stack would be preserved and restored when >>>>> switching between execution stacks. That would allow implementing >>>>> per-thread statistical call graph view in Perf tools, fully based >>>>> on HW capabilities. It could be advantageous for some cases, in >>>>> comparison with traditional dwarf based call graph. >>>> >>>> This is already supported when you use LBR call stack mode >>>> (perf record --call-graph lbr) >>> >>> Which kernel versions does it make sense to try? >>> >> >> The optimization for LBR call stack has been merged into 4.19. >> commit id: 8b077e4a69bef5c4121426e99497975860191e53 >> perf/x86/intel/lbr: Optimize context switches for the LBR call stack > > I think he mean support for LBR call stack in general. This has been there > for a long time (since Haswell) Any reasonable kernel version should > support it. > Oh I see. Yes, the feature of LBR call stack was added long time ago. But I still recommend 4.19. Because it includes a recent bug fix for LBR call stack. commit id: 0592e57b24e7e05ec1f4c50b9666c013abff7017 perf/x86/intel/lbr: Fix incomplete LBR call stack Thanks, Kan