From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932232AbWAZTnF (ORCPT ); Thu, 26 Jan 2006 14:43:05 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932257AbWAZTnF (ORCPT ); Thu, 26 Jan 2006 14:43:05 -0500 Received: from e33.co.us.ibm.com ([32.97.110.151]:1701 "EHLO e33.co.us.ibm.com") by vger.kernel.org with ESMTP id S932232AbWAZTnE (ORCPT ); Thu, 26 Jan 2006 14:43:04 -0500 Date: Fri, 27 Jan 2006 01:12:33 +0530 From: Dipankar Sarma To: "Paul E. McKenney" Cc: Andrew Morton , Linus Torvalds , linux-kernel@vger.kernel.org Subject: Re: [patch 1/2] rcu batch tuning Message-ID: <20060126194233.GG4166@in.ibm.com> Reply-To: dipankar@in.ibm.com References: <20060126184010.GD4166@in.ibm.com> <20060126184127.GE4166@in.ibm.com> <20060126193317.GD6182@us.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060126193317.GD6182@us.ibm.com> User-Agent: Mutt/1.5.10i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 26, 2006 at 11:33:17AM -0800, Paul E. McKenney wrote: > On Fri, Jan 27, 2006 at 12:11:27AM +0530, Dipankar Sarma wrote: > > > > This patch adds new tunables for RCU queue and finished batches. > > There are two types of controls - number of completed RCU updates > > invoked in a batch (blimit) and monitoring for high rate of > > incoming RCUs on a cpu (qhimark, qlowmark). By default, > > the per-cpu batch limit is set to a small value. If > > the input RCU rate exceeds the high watermark, we do two things - > > force quiescent state on all cpus and set the batch limit > > of the CPU to INTMAX. Setting batch limit to INTMAX forces all > > finished RCUs to be processed in one shot. If we have more than > > INTMAX RCUs queued up, then we have bigger problems anyway. > > Once the incoming queued RCUs fall below the low watermark, the batch limit > > is set to the default. > > Looks good to me! We might have to have more sophisticated adjustment > of blimit, but starting simple is definitely the right way to go. Yes. Once I am set up to do latency measurements, I will look at the possible need for more sophisticated adjustment of blimit. Thanks Dipankar