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 CF306ECE562 for ; Mon, 17 Sep 2018 07:57:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8D6B4214C2 for ; Mon, 17 Sep 2018 07:57:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8D6B4214C2 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 S1728081AbeIQNYG (ORCPT ); Mon, 17 Sep 2018 09:24:06 -0400 Received: from mga18.intel.com ([134.134.136.126]:3339 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726652AbeIQNYG (ORCPT ); Mon, 17 Sep 2018 09:24:06 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Sep 2018 00:57:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,384,1531810800"; d="scan'208";a="74882249" Received: from linux.intel.com ([10.54.29.200]) by orsmga006.jf.intel.com with ESMTP; 17 Sep 2018 00:57:42 -0700 Received: from [10.125.252.52] (abudanko-mobl.ccr.corp.intel.com [10.125.252.52]) by linux.intel.com (Postfix) with ESMTP id 3130658014B; Mon, 17 Sep 2018 00:57:39 -0700 (PDT) Subject: Re: [PATCH] perf/x86/intel/lbr: Optimize context switches for LBR To: linux-kernel-owner@vger.kernel.org, Andi Kleen Cc: 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: Alexey Budankov Organization: Intel Corp. Message-ID: <0ffedf2e-0557-1351-045c-2758b207f019@linux.intel.com> Date: Mon, 17 Sep 2018 10:57:38 +0300 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: Content-Type: text/plain; charset=utf-8 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 Hello Kan and Andi, On 14.09.2018 17:57, linux-kernel-owner@vger.kernel.org wrote: > > > 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 for your support. Best regards, Alexey > > Thanks, > Kan >