From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757798Ab3FTKid (ORCPT ); Thu, 20 Jun 2013 06:38:33 -0400 Received: from nat28.tlf.novell.com ([130.57.49.28]:54624 "EHLO nat28.tlf.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756915Ab3FTKic convert rfc822-to-8bit (ORCPT ); Thu, 20 Jun 2013 06:38:32 -0400 Message-Id: <51C2F7C102000078000DF504@nat28.tlf.novell.com> X-Mailer: Novell GroupWise Internet Agent 12.0.2 Date: Thu, 20 Jun 2013 11:38:25 +0100 From: "Jan Beulich" To: "David Vrabel" Cc: "John Stultz" , "Thomas Gleixner" , , "Konrad Rzeszutek Wilk" , Subject: Re: [Xen-devel] [PATCH 1/4] xen: disable non-boot VCPUs during suspend References: <1371655523-15609-1-git-send-email-david.vrabel@citrix.com> <1371655523-15609-2-git-send-email-david.vrabel@citrix.com> In-Reply-To: <1371655523-15609-2-git-send-email-david.vrabel@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 8BIT Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org >>> On 19.06.13 at 17:25, David Vrabel wrote: > syscore_suspend() and syscore_resume() expect there to be only one > online CPU. e.g., hrtimers_resume() only triggers events for the > current CPU. Xen's suspend path was leaving all VCPUs online and then > attempting to fixup problems afterwards (e.g., with an explicit call > to clock_was_set() to trigger pending high resolution timers). > > Instead, disable non-boot CPUs before calling stop_machine() and > reenable them afterwards. In XenoLinux the so called "fast suspend" mode was specifically added for performance reasons, and it looks like to date pv-ops only ever supported that mode. So one question is whether there's going to be any bad performance effect from this. The other question is that about retaining the use of stop_machine() then - it seems pretty pointless if you already bring down all other CPUs. Jan