Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759614AbZAGPQ1 (ORCPT ); Wed, 7 Jan 2009 10:16:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751623AbZAGPQR (ORCPT ); Wed, 7 Jan 2009 10:16:17 -0500 Received: from casper.infradead.org ([85.118.1.10]:39972 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751348AbZAGPQR (ORCPT ); Wed, 7 Jan 2009 10:16:17 -0500 Subject: Re: [PATCH] configure HAVE_UNSTABLE_SCHED_CLOCK for SGI_SN systems From: Peter Zijlstra To: Dimitri Sivanich Cc: Robin Holt , Nick Piggin , "Luck, Tony" , "linux-ia64@vger.kernel.org" , Greg KH , "linux-kernel@vger.kernel.org" , Gregory Haskins , Tony Luck In-Reply-To: <20090107133230.GA28694@sgi.com> References: <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> <20090107030030.GH3390@wotan.suse.de> <1231313289.11687.172.camel@twins> <20090107094328.GD3850@sgi.com> <1231322037.11687.178.camel@twins> <20090107133230.GA28694@sgi.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Wed, 07 Jan 2009 16:16:14 +0100 Message-Id: <1231341374.11687.303.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.24.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 786 Lines: 18 On Wed, 2009-01-07 at 07:32 -0600, Dimitri Sivanich wrote: > Peter, > > On Wed, Jan 07, 2009 at 10:53:57AM +0100, Peter Zijlstra wrote: > > > > Clock state is kept per-cpu, and locked with a spinlock. When we request > > Admittedly I have not looked at this possibility too closely, but my > initial concern upon looking at sched_clock_cpu() for the UNSTABLE > case was the lock_double_clock() and what sort of contention that > might cause on larger systems under certain conditions. Similar contention would already exist on rq->lock. -- 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/