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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 E706FC433ED for ; Fri, 21 May 2021 00:15:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BDD74610CB for ; Fri, 21 May 2021 00:15:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234733AbhEUARP (ORCPT ); Thu, 20 May 2021 20:17:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:52870 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234612AbhEUARN (ORCPT ); Thu, 20 May 2021 20:17:13 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id D794F6109F; Fri, 21 May 2021 00:15:51 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1621556151; bh=KN/xo1lyoIiciG9V+VqlWx19KUfp8J5f+WyREaqusoU=; h=Date:From:To:Cc:Subject:Reply-To:References:In-Reply-To:From; b=e6JBFVBMjMOtGuOw3ilgjfYaLUsfqnviBEew5unIppvInUsZXyizRTMSrQSWvYHuA kkfJktbLa2XxBrODrZqhxlrG66hNiDXSWcoK/krfiry6dPQb7t121a5YirPmzeJc2E s9qv2ejQWrwtmnPTvyeDV6eMta/yfZgNRvkJBPw/KBtlCe9W9o+FjbovdfnZdk3e0n uY9l2hRjQTvbKvrnhcN9OieseLRnBSJByVwTT88p6RRizfqwvhJ6XfoP7WE0fZ3E9J nx3b37oSJdq51xp/fOly1Opm6vCbxnVEj2OC21F5xFj/wP0xUYMZNbuVIS+DsNkeGu EE783aWZleRCA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id A05D15C023D; Thu, 20 May 2021 17:15:51 -0700 (PDT) Date: Thu, 20 May 2021 17:15:51 -0700 From: "Paul E. McKenney" To: Sergey Senozhatsky Cc: Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , Suleiman Souhlal , rcu@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] rcu/tree: consider time a VM was suspended Message-ID: <20210521001551.GS4441@paulmck-ThinkPad-P17-Gen-1> Reply-To: paulmck@kernel.org References: <20210516102716.689596-1-senozhatsky@chromium.org> <20210517162312.GG4441@paulmck-ThinkPad-P17-Gen-1> <20210518231514.GS4441@paulmck-ThinkPad-P17-Gen-1> <20210520145708.GK4441@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Fri, May 21, 2021 at 07:34:41AM +0900, Sergey Senozhatsky wrote: > On (21/05/20 07:57), Paul E. McKenney wrote: > > > > > > Sounds good. I can cook a patch and run some tests. > > > Or do you want to send a patch? > > > > Given that you have the test setup, things might go faster if you do > > the patch, especially taking timezones into consideration. Of course, > > if you run into difficulties, you know where to find me. > > OK. Sounds good to me. > > > > While VCPU-2 has PVCLOCK_GUEST_STOPPED set (resuming) and is in > > > check_cpu_stall(), the VCPU-3 is executing: > > > > > > apic_timer_interrupt() > > > tick_irq_enter() > > > tick_do_update_jiffies64() > > > do_timer() > > > > OK, but the normal grace period time is way less than one second, and > > the stall timeout in mainline is 21 seconds, so that would be a -lot- > > of jiffies of skew. Or does the restarting really take that long a time? > > That's a good question. I see huge jiffies spike in the logs. > I suspect that resuming a VM can take some time, especially on a "not > powerful at all" overcommitted host (more virtual CPUs than physical > ones). I really am just asking the question. ;-) After all, if restarting a VM can take that long, then it can take that long. Thanx, Paul