Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759786AbZAGDAm (ORCPT ); Tue, 6 Jan 2009 22:00:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753838AbZAGDAc (ORCPT ); Tue, 6 Jan 2009 22:00:32 -0500 Received: from ns2.suse.de ([195.135.220.15]:58768 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753120AbZAGDAc (ORCPT ); Tue, 6 Jan 2009 22:00:32 -0500 Date: Wed, 7 Jan 2009 04:00:30 +0100 From: Nick Piggin To: Peter Zijlstra Cc: Robin Holt , "Luck, Tony" , Dimitri Sivanich , "linux-ia64@vger.kernel.org" , Greg KH , "linux-kernel@vger.kernel.org" , Gregory Haskins , Tony Luck Subject: Re: [PATCH] configure HAVE_UNSTABLE_SCHED_CLOCK for SGI_SN systems Message-ID: <20090107030030.GH3390@wotan.suse.de> References: <20090106162741.GA7991@sgi.com> <57C9024A16AD2D4C97DC78E552063EA35CB95575@orsmsx505.amr.corp.intel.com> <20090106201950.GA3850@sgi.com> <57C9024A16AD2D4C97DC78E552063EA35CB955B4@orsmsx505.amr.corp.intel.com> <1231275441.11687.110.camel@twins> <20090106225054.GB3850@sgi.com> <1231283763.11687.135.camel@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1231283763.11687.135.camel@twins> User-Agent: Mutt/1.5.9i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 916 Lines: 20 On Wed, Jan 07, 2009 at 12:16:03AM +0100, Peter Zijlstra wrote: > > > > But doesn't scheduler tick advance the rq->clock? Why do the others > > need to fiddle with a remote runqueue's clock? When that cpu starts > > taking ticks again, it will update it's rq->clock field and start the > > processes. I guess I am a lot underinformed about the new scheduler > > design. > > We try to do better than tick based time accounting these days. But if you contain the drift to within one tick, it shouldn't be much problem to just truncate negative deltas I would have thought? The time between events on different CPUs is pretty fuzzy at the ns level anyway, I think ;) -- 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/