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 B9410C282DD for ; Wed, 8 Jan 2020 15:50:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8333D2072A for ; Wed, 8 Jan 2020 15:50:52 +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="gzhPPRxb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728520AbgAHPuv (ORCPT ); Wed, 8 Jan 2020 10:50:51 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:43552 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726186AbgAHPuv (ORCPT ); Wed, 8 Jan 2020 10:50:51 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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=ZclNq8Gr7pU/JCTXFFTTfRWQ9njV8jVe1K8Bz3Pzsz0=; b=gzhPPRxbWxKaI0bZ0WbwrbmXR xlSTgzecSP6dVTnbBkKg9qkpoHergsjs7+VQhOuVJA5yY18MfdusUj+sC1u2dmzd3fG0V4ncwLsb8 yLJnCGRrWQ9v5J3QN2xm8R22Kh6EW/NR93PLH/hFGYY2+0PZeb7T1R8Q5QTjZd94Tje8wUD/f+d7l ongVbMqAms69fs7UDvXoOHKwVx5qtVYtSE0LsTrLZiF7/V8/wEMAiLMk+mA8ql4KJJoKWHf0D+kd0 iWreXHPDj0vq8sBh5hYqpY7/ti2FbxBUbBYAspjZmI8w23DD6uxivJ8guinjSEH0/HvTTYnU9Av7C dAcyzKaWg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=noisy.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.92.3 #3 (Red Hat Linux)) id 1ipDbX-0002mT-5L; Wed, 08 Jan 2020 15:50:43 +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 720FD30025A; Wed, 8 Jan 2020 16:49:07 +0100 (CET) Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 754D62B6157AC; Wed, 8 Jan 2020 16:50:40 +0100 (CET) Date: Wed, 8 Jan 2020 16:50:40 +0100 From: Peter Zijlstra To: Wanpeng Li Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Thomas Gleixner , Marcelo Tosatti , Konrad Rzeszutek Wilk , KarimAllah , Vincent Guittot , Ingo Molnar , Ankur Arora Subject: Re: [PATCH RFC] sched/fair: Penalty the cfs task which executes mwait/hlt Message-ID: <20200108155040.GB2827@hirez.programming.kicks-ass.net> References: <1578448201-28218-1-git-send-email-wanpengli@tencent.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1578448201-28218-1-git-send-email-wanpengli@tencent.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 Wed, Jan 08, 2020 at 09:50:01AM +0800, Wanpeng Li wrote: > From: Wanpeng Li > > To deliver all of the resources of a server to instances in cloud, there are no > housekeeping cpus reserved. libvirtd, qemu main loop, kthreads, and other agent/tools > etc which can't be offloaded to other hardware like smart nic, these stuff will > contend with vCPUs even if MWAIT/HLT instructions executed in the guest. > > The is no trap and yield the pCPU after we expose mwait/hlt to the guest [1][2], > the top command on host still observe 100% cpu utilization since qemu process is > running even though guest who has the power management capability executes mwait. > Actually we can observe the physical cpu has already enter deeper cstate by > powertop on host. > > For virtualization, there is a HLT activity state in CPU VMCS field which indicates > the logical processor is inactive because it executed the HLT instruction, but > SDM 24.4.2 mentioned that execution of the MWAIT instruction may put a logical > processor into an inactive state, however, this VMCS field never reflects this > state. So far I think I can follow, however it does not explain who consumes this VMCS state if it is set and how that helps. Also, this: > This patch avoids fine granularity intercept and reschedule vCPU if MWAIT/HLT > instructions executed, because it can worse the message-passing workloads which > will switch between idle and running frequently in the guest. Lets penalty the > vCPU which is long idle through tick-based sampling and preemption. is just complete gibberish. And I have no idea what problem you're trying to solve how. Also, I don't think the TSC/MPERF ratio is architected, we can't assume this is true for everything that has APERFMPERF. /me tries to reconstruct intent from patch So what you're doing is, mark the CPU 'idle' when the MPERF/TSC ratio < 1%, and then frob the vruntime such that it will hopefully preempt. That's pretty disgusting. Please, write a coherent problem statement and justify the magic choices. This is unreviewable.