Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935768AbaDJVaO (ORCPT ); Thu, 10 Apr 2014 17:30:14 -0400 Received: from e32.co.us.ibm.com ([32.97.110.150]:60373 "EHLO e32.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753612AbaDJVaM (ORCPT ); Thu, 10 Apr 2014 17:30:12 -0400 Date: Thu, 10 Apr 2014 14:30:03 -0700 From: "Paul E. McKenney" To: Steven Rostedt Cc: Peter Zijlstra , Sebastian Andrzej Siewior , Clark Williams , LKML , linux-rt-users , Mike Galbraith , Paul Gortmaker , Thomas Gleixner , Frederic Weisbecker , Ingo Molnar Subject: Re: [RFC PATCH RT] rwsem: The return of multi-reader PI rwsems Message-ID: <20140410213003.GA21760@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20140409151922.5fa5d999@gandalf.local.home> <20140410094430.56ca9ee1@sluggy.gateway.2wire.net> <5346B2C8.6000207@linutronix.de> <20140410153617.GN10526@twins.programming.kicks-ass.net> <20140410151741.617f86d9@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140410151741.617f86d9@gandalf.local.home> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14041021-0928-0000-0000-00000124CAA9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 10, 2014 at 03:17:41PM -0400, Steven Rostedt wrote: > On Thu, 10 Apr 2014 17:36:17 +0200 > Peter Zijlstra wrote: > > > > It defaults to the total number of CPUs in the system, given the default > > setup (all CPUs in a single balance domain), this should result in all > > CPUs working concurrently on the boosted read sides. > > Unfortunately, it currently defaults to the number of possible CPUs in > the system. I should probably move the default assignment to after SMP > is setup. Currently it happens in early boot before all the CPUs are > running. On boot up, the limit is set to NR_CPUS which should be much > higher than what the system has, but shouldn't matter during boot. But > after all the CPUs are up and running, it can lower it to online CPUs. Another approach is to use nr_cpu_ids, which is the maximum number of CPUs that the particular booting system could ever have. I use this in RCU to resize the data structures down from their NR_CPUS compile-time hugeness. Thanx, Paul > I think I'll go and make v3 of this patch. > > -- Steve > -- 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/