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=-4.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 3BA1BC28CC0 for ; Wed, 29 May 2019 14:42:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 18FEE23A78 for ; Wed, 29 May 2019 14:42:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726697AbfE2Omc (ORCPT ); Wed, 29 May 2019 10:42:32 -0400 Received: from mga07.intel.com ([134.134.136.100]:21770 "EHLO mga07.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726275AbfE2Omc (ORCPT ); Wed, 29 May 2019 10:42:32 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by orsmga105.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 May 2019 07:42:31 -0700 X-ExtLoop1: 1 Received: from linux.intel.com ([10.54.29.200]) by fmsmga008.fm.intel.com with ESMTP; 29 May 2019 07:42:31 -0700 Received: from [10.251.0.80] (kliang2-mobl.ccr.corp.intel.com [10.251.0.80]) (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 72BEE58054E; Wed, 29 May 2019 07:42:30 -0700 (PDT) Subject: Re: [PATCH 4/9] perf/x86/intel: Support hardware TopDown metrics To: Peter Zijlstra Cc: acme@kernel.org, mingo@redhat.com, linux-kernel@vger.kernel.org, tglx@linutronix.de, jolsa@kernel.org, eranian@google.com, alexander.shishkin@linux.intel.com, ak@linux.intel.com References: <20190521214055.31060-1-kan.liang@linux.intel.com> <20190521214055.31060-5-kan.liang@linux.intel.com> <20190528134845.GQ2623@hirez.programming.kicks-ass.net> <2d693635-9697-2cf5-54dc-b91da4dfd14f@linux.intel.com> <20190529075720.GB2623@hirez.programming.kicks-ass.net> From: "Liang, Kan" Message-ID: <09770caf-e717-5b11-d11f-f30cb027bb05@linux.intel.com> Date: Wed, 29 May 2019 10:42:29 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190529075720.GB2623@hirez.programming.kicks-ass.net> 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 5/29/2019 3:57 AM, Peter Zijlstra wrote: > On Tue, May 28, 2019 at 02:24:56PM -0400, Liang, Kan wrote: >> >> >> On 5/28/2019 9:48 AM, Peter Zijlstra wrote: >>> On Tue, May 21, 2019 at 02:40:50PM -0700, kan.liang@linux.intel.com wrote: >>>> diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h >>>> index b980b9e95d2a..0d7081434d1d 100644 >>>> --- a/include/linux/perf_event.h >>>> +++ b/include/linux/perf_event.h >>>> @@ -133,6 +133,11 @@ struct hw_perf_event { >>>> struct hw_perf_event_extra extra_reg; >>>> struct hw_perf_event_extra branch_reg; >>>> + >>>> + u64 saved_metric; >>>> + u64 saved_slots; >>>> + u64 last_slots; >>>> + u64 last_metric; >>> >>> This is really sad, and I'm thinking much of that really isn't needed >>> anyway, due to how you're not using some of the other fields. >> >> If we don't cache the value, we have to update all metrics events when >> reading any metrics event. I think that could bring high overhead. > > Since you don't support sampling, or even 'normal' functionality on this > FIXED3/SLOTS thing, you'll not use prev_count, sample_period, > last_period, period_left, interrupts_seq, interrupts, freq_time_stamp > and freq_count_stamp. > > So why do you then need to grow the data structure with 4 more nonsense > fields? > > Also, I'm not sure what you need those last things for, you reset the > value to 0 every time you read them, there is no delta to track. > The 'last things' are only for per-thread Topdown RDPMC. We have to save/restore slots and metrics value in context switch. It's used to calculate the delta between thread shced in and current read/sched out. I will split the patch into several patches, and try to make things clear. Thanks, Kan