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=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 ED1E8C33CAD for ; Mon, 13 Jan 2020 12:36:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BCA242081E for ; Mon, 13 Jan 2020 12:36:31 +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="gGBpvza+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727222AbgAMMgb (ORCPT ); Mon, 13 Jan 2020 07:36:31 -0500 Received: from merlin.infradead.org ([205.233.59.134]:33104 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726074AbgAMMga (ORCPT ); Mon, 13 Jan 2020 07:36:30 -0500 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=pJ1ajlLalSb1lnSWYzrZ3l95cR2DmPwww/lMVi/JmI8=; b=gGBpvza+J9GkHFPjo1zmKUMn+ anND46i/9BDOMeU7JceBSIFp5gTujs10uCYe3iG/R06NirqZMIRQDsVgmLY2AHkc4afOCqFnSh4vB 0Rpdp5jF4TQjAY021SKBbvURAawSBKXRrk0+vrq88VzjFhIWcD2ijHHnRFrBBhG6zQu+8QY9P/0cD tx8mZDbwkRuXktfh0FpKRJAGinJoDNMkFKXUk6klwdBLzi1iLUAVIe8i6LIQOHt7ivCNipOmVLubG OaTHrpXuli4LcHWKpVtzItd3N2qmBqGtCms5UVV3StB6soEF9YE8JpmYyQztuMnhUDEDIEZ74VRGX iEUqhlGmw==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1iqyws-000416-I6; Mon, 13 Jan 2020 12:36:02 +0000 Received: from hirez.programming.kicks-ass.net (hirez.programming.kicks-ass.net [192.168.1.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by noisy.programming.kicks-ass.net (Postfix) with ESMTPS id 33C63304121; Mon, 13 Jan 2020 13:34:23 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 8A4392B6B2F93; Mon, 13 Jan 2020 13:35:58 +0100 (CET) Date: Mon, 13 Jan 2020 13:35:58 +0100 From: Peter Zijlstra To: Paolo Bonzini Cc: Wanpeng Li , LKML , kvm , Thomas Gleixner , Marcelo Tosatti , Konrad Rzeszutek Wilk , KarimAllah , Vincent Guittot , Ingo Molnar , Ankur Arora , christopher.s.hall@intel.com, hubert.chrzaniuk@intel.com, len.brown@intel.com, thomas.lendacky@amd.com, rjw@rjwysocki.net Subject: Re: [PATCH RFC] sched/fair: Penalty the cfs task which executes mwait/hlt Message-ID: <20200113123558.GF2827@hirez.programming.kicks-ass.net> References: <1578448201-28218-1-git-send-email-wanpengli@tencent.com> <20200108155040.GB2827@hirez.programming.kicks-ass.net> <00d884a7-d463-74b4-82cf-9deb0aa70971@redhat.com> <20200113104314.GU2844@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Mon, Jan 13, 2020 at 12:52:20PM +0100, Paolo Bonzini wrote: > On 13/01/20 11:43, Peter Zijlstra wrote: > > So the very first thing we need to get sorted is that MPERF/TSC ratio > > thing. TurboStat does it, but has 'funny' hacks on like: > > > > b2b34dfe4d9a ("tools/power turbostat: KNL workaround for %Busy and Avg_MHz") > > > > and I imagine that there's going to be more exceptions there. You're > > basically going to have to get both Intel and AMD to commit to this. > > > > IFF we can get concensus on MPERF/TSC, then yes, that is a reasonable > > way to detect a VCPU being idle I suppose. I've added a bunch of people > > who seem to know about this. > > > > Anyone, what will it take to get MPERF/TSC 'working' ? > > Do we really need MPERF/TSC for this use case, or can we just track > APERF as well and do MPERF/APERF to compute the "non-idle" time? So MPERF runs at fixed frequency (when !IDLE and typically the same frequency as TSC), APERF runs at variable frequency (when !IDLE) depending on DVFS state. So APERF/MPERF gives the effective frequency of the core, but since both stop during IDLE, it will not be a good indication of IDLE. Otoh, TSC doesn't stop in idle (.oO this depends on X86_FEATURE_CONSTANT_TSC) and therefore the MPERF/TSC ratio gives how much !idle time there was between readings.