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=-5.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 C0CC4C04AB3 for ; Wed, 29 May 2019 07:57:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8FFA02070D for ; Wed, 29 May 2019 07:57:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="M3EnNLp1" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726131AbfE2H51 (ORCPT ); Wed, 29 May 2019 03:57:27 -0400 Received: from merlin.infradead.org ([205.233.59.134]:59908 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725895AbfE2H51 (ORCPT ); Wed, 29 May 2019 03:57:27 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=merlin.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=wFXL69+e9FA8T4bdG84SBXZny14soC0SfpQJDLWkYx4=; b=M3EnNLp1Cc9fiAjrltyjRQQfH YyyDpA9ZxG8zhyWf+mBrd+4sQAkmFloMRli3OaTx64lNU8GvoK6ZlYVGfoKzjDAfxHFTpCCI6oGoL FQEbcCJZ2MkxSrGAdOn/v3z6m5IXvXUXw5EUT9l/QxdNjul4FctOiJpE1sLApwKv2deMk6Zc0SBpq yCCKndWjw1+qmuB/9ZtXju8YJlLmf5bYSQdy+N2kf3P+KDIoSwoatgtXSdIahv5yam5lSt1j2SSvL Z4FVqGdTcTNRLZGNdwI00M4IM4BWkA+JKi+DOsYnBjXtQ8IzqBnZF84wG2lmQMzsE8YgnFl8RzZR+ EPPIX7X7g==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hVtSc-0002IT-1T; Wed, 29 May 2019 07:57:22 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id BCAA6201A7E41; Wed, 29 May 2019 09:57:20 +0200 (CEST) Date: Wed, 29 May 2019 09:57:20 +0200 From: Peter Zijlstra To: "Liang, Kan" 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 Subject: Re: [PATCH 4/9] perf/x86/intel: Support hardware TopDown metrics Message-ID: <20190529075720.GB2623@hirez.programming.kicks-ass.net> 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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2d693635-9697-2cf5-54dc-b91da4dfd14f@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.