From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754462Ab0AHXxm (ORCPT ); Fri, 8 Jan 2010 18:53:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754372Ab0AHXxl (ORCPT ); Fri, 8 Jan 2010 18:53:41 -0500 Received: from tomts5.bellnexxia.net ([209.226.175.25]:40577 "EHLO tomts5-srv.bellnexxia.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753893Ab0AHXxk (ORCPT ); Fri, 8 Jan 2010 18:53:40 -0500 Date: Fri, 8 Jan 2010 18:53:38 -0500 From: Mathieu Desnoyers To: Steven Rostedt Cc: paulmck@linux.vnet.ibm.com, Oleg Nesterov , Peter Zijlstra , linux-kernel@vger.kernel.org, Ingo Molnar , akpm@linux-foundation.org, josh@joshtriplett.org, tglx@linutronix.de, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, laijs@cn.fujitsu.com, dipankar@in.ibm.com Subject: Re: [RFC PATCH] introduce sys_membarrier(): process-wide memory barrier Message-ID: <20100108235338.GA18050@Krystal> References: <20100107044007.GA22863@Krystal> <1262852862.4049.78.camel@laptop> <20100107183010.GA14980@redhat.com> <20100107183946.GL6764@linux.vnet.ibm.com> <1262890782.28171.3738.camel@gandalf.stny.rr.com> <20100107191657.GN6764@linux.vnet.ibm.com> <1262893243.28171.3753.camel@gandalf.stny.rr.com> <20100107205830.GR6764@linux.vnet.ibm.com> <1262900140.28171.3773.camel@gandalf.stny.rr.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Content-Disposition: inline In-Reply-To: <1262900140.28171.3773.camel@gandalf.stny.rr.com> X-Editor: vi X-Info: http://krystal.dyndns.org:8080 X-Operating-System: Linux/2.6.27.31-grsec (i686) X-Uptime: 18:51:55 up 23 days, 8:10, 6 users, load average: 0.24, 0.14, 0.10 User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Steven Rostedt (rostedt@goodmis.org) wrote: > Well, if we just grab the task_rq(task)->lock here, then we should be > OK? We would guarantee that curr is either the task we want or not. > Hrm, I just tested it, and there seems to be a significant performance penality involved with taking these locks for each CPU, even with just 8 cores. So if we can do without the locks, that would be preferred. Thanks, Mathieu -- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68