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_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 398E2C48BD6 for ; Wed, 26 Jun 2019 19:21:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 010DE217D9 for ; Wed, 26 Jun 2019 19:21:23 +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="uxdz562l" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726503AbfFZTVV (ORCPT ); Wed, 26 Jun 2019 15:21:21 -0400 Received: from merlin.infradead.org ([205.233.59.134]:47614 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726227AbfFZTVV (ORCPT ); Wed, 26 Jun 2019 15:21:21 -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-Transfer-Encoding: Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To:From:Date: Sender:Reply-To: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=V0jLxYAn+nqGzG0R8aNQz9MoPnspgo1/uyky7k+5p+k=; b=uxdz562loKTGsLdJtWlp/cwLTe GT+1eM+P/R1wFx79woFof2wJjB3Y9vYfQmzpdcIaIU83pKIZREcTNlzD+0rQbxJwujSJKNBgvz9IV LfVVZ6NxKM9RyPIIiCojd62gd1v+4J2V/GBk5FOPvpYUHzl3whUUNTdAOcHZTcjTpPdM/mz61drdu oo61DWBQRp82BvcQCC0MBkBHPF41qM8CnNL0XyGaV4JF23Vez0fIIQIxizHvdYj+Y5W2IPqa2Beyi zcX6IUhMf3KUcXS+1oP8DCrEk6svsMb7I5V++fYKN5uW4u74Lcyxrw/VVZ73r6dddBMWyTsKxrZL5 l/KTyAEg==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by merlin.infradead.org with esmtpsa (Exim 4.92 #3 (Red Hat Linux)) id 1hgDTb-0001Mk-E0; Wed, 26 Jun 2019 19:21:03 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id A49CC209CEDA7; Wed, 26 Jun 2019 21:21:00 +0200 (CEST) Date: Wed, 26 Jun 2019 21:21:00 +0200 From: Peter Zijlstra To: "Raslan, KarimAllah" Cc: "tglx@linutronix.de" , "konrad.wilk@oracle.com" , "boris.ostrovsky@oracle.com" , "joao.m.martins@oracle.com" , "kvm@vger.kernel.org" , "kernellwp@gmail.com" , "linux-kernel@vger.kernel.org" , "mtosatti@redhat.com" , "pbonzini@redhat.com" , "ankur.a.arora@oracle.com" , "rkrcmar@redhat.com" Subject: Re: cputime takes cstate into consideration Message-ID: <20190626192100.GP3419@hirez.programming.kicks-ass.net> References: <20190626145413.GE6753@char.us.oracle.com> <20190626161608.GM3419@hirez.programming.kicks-ass.net> <20190626183016.GA16439@char.us.oracle.com> <1561575336.25880.7.camel@amazon.de> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1561575336.25880.7.camel@amazon.de> 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, Jun 26, 2019 at 06:55:36PM +0000, Raslan, KarimAllah wrote: > If the host is completely in no_full_hz mode and the pCPU is dedicated to a  > single vCPU/task (and the guest is 100% CPU bound and never exits), you would  > still be ticking in the host once every second for housekeeping, right? Would  > not updating the mwait-time once a second be enough here? People are trying very hard to get rid of that remnant tick. Lets not add dependencies to it. IMO this is a really stupid issue, 100% time is correct if the guest does idle in pinned vcpu mode.