From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1030421AbWAXJXC (ORCPT ); Tue, 24 Jan 2006 04:23:02 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1030424AbWAXJXC (ORCPT ); Tue, 24 Jan 2006 04:23:02 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:21640 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1030422AbWAXJXA (ORCPT ); Tue, 24 Jan 2006 04:23:00 -0500 Date: Tue, 24 Jan 2006 10:23:30 +0100 From: Ingo Molnar To: "Paul E. McKenney" Cc: Lee Revell , linux-kernel , Linus Torvalds Subject: Re: RCU latency regression in 2.6.16-rc1 Message-ID: <20060124092330.GA7060@elte.hu> References: <1138089139.2771.78.camel@mindpipe> <20060124075640.GA24806@elte.hu> <1138089483.2771.81.camel@mindpipe> <20060124080157.GA25855@elte.hu> <1138090078.2771.88.camel@mindpipe> <20060124081301.GC25855@elte.hu> <1138090527.2771.91.camel@mindpipe> <20060124091730.GA31204@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060124091730.GA31204@us.ibm.com> User-Agent: Mutt/1.4.2.1i X-ELTE-SpamScore: -2.2 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.2 required=5.9 tests=ALL_TRUSTED,AWL autolearn=no SpamAssassin version=3.0.3 -2.8 ALL_TRUSTED Did not pass through any untrusted hosts 0.6 AWL AWL: From: address is in the auto white-list X-ELTE-VirusStatus: clean Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Paul E. McKenney wrote: > > Have not tested yet but it appears that will reduce it substantially: > > > > $ grep "dst_destroy (dst_rcu_free)" /proc/latency_trace | wc -l > > 3027 > > > > This implies the latency would be reduced to ~4ms, still not great but > > it will be overshadowed by rt_run_flush/rt_garbage_collect. > > The other patch to try would be Dipankar Sarma's patch at: > > http://marc.theaimsgroup.com/?l=linux-kernel&m=113657112726596&w=2 > > This patch was primarily designed to reduce memory overhead, but given > that it tends to reduce batch size, it should also reduce latency. if this solves Lee's problem, i think we should apply this as a fix, and get it into v2.6.16. The patch looks straightforward and correct to me. Ingo