Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752406AbbGVT2o (ORCPT ); Wed, 22 Jul 2015 15:28:44 -0400 Received: from e33.co.us.ibm.com ([32.97.110.151]:47749 "EHLO e33.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752068AbbGVT2m (ORCPT ); Wed, 22 Jul 2015 15:28:42 -0400 X-Helo: d03dlp03.boulder.ibm.com X-MailFrom: paulmck@linux.vnet.ibm.com X-RcptTo: linux-kernel@vger.kernel.org Date: Wed, 22 Jul 2015 12:28:34 -0700 From: "Paul E. McKenney" To: Christoph Lameter Cc: Andy Lutomirski , Chris Metcalf , Gilad Ben Yossef , Steven Rostedt , Ingo Molnar , Peter Zijlstra , Andrew Morton , Rik van Riel , Tejun Heo , Frederic Weisbecker , Thomas Gleixner , Viresh Kumar , "linux-doc@vger.kernel.org" , Linux API , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v4 1/5] nohz_full: add support for "cpu_isolated" mode Message-ID: <20150722192834.GA32511@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <1436817481-8732-1-git-send-email-cmetcalf@ezchip.com> <1436817481-8732-2-git-send-email-cmetcalf@ezchip.com> <55A4271B.9040506@ezchip.com> <55AE993E.6040501@ezchip.com> <20150721203622.GX3717@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 15072219-0009-0000-0000-00000CB1AAC6 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1232 Lines: 29 On Wed, Jul 22, 2015 at 08:57:45AM -0500, Christoph Lameter wrote: > On Tue, 21 Jul 2015, Paul E. McKenney wrote: > > > > > In the current version, there's also the vmstat_update() that > > > > may schedule delayed work and interrupt the core again > > > > shortly before realizing that there are no more counter updates > > > > happening, at which point it quiesces. Currently we handle > > > > this in cpu_isolated mode simply by spinning and waiting for > > > > the timer interrupts to complete. > > > > > > Perhaps we should fix that? > > > > Didn't Christoph Lameter fix this? Or is this an additional problem? > > Well the vmstat update must realize first that there are no outstanding > updates before switching itself off. So typically there is one extra tick. > But we could add another function that will simply fold the differential > immediately and turn the kworker task in the expectation that the > processor will stay quiet. Got it, thank you! Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/