Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756129Ab2EVRHu (ORCPT ); Tue, 22 May 2012 13:07:50 -0400 Received: from www.linutronix.de ([62.245.132.108]:39404 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750826Ab2EVRHt (ORCPT ); Tue, 22 May 2012 13:07:49 -0400 Date: Tue, 22 May 2012 19:07:46 +0200 (CEST) From: Thomas Gleixner To: Steven Rostedt cc: LKML , RT , Clark Williams , Peter Zijlstra Subject: Re: [RFC][PATCH RT] rwsem_rt: Another (more sane) approach to mulit reader rt locks In-Reply-To: <1337705539.13348.81.camel@gandalf.stny.rr.com> Message-ID: References: <1337090625.14207.304.camel@gandalf.stny.rr.com> <1337701801.13348.56.camel@gandalf.stny.rr.com> <1337705539.13348.81.camel@gandalf.stny.rr.com> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1244 Lines: 30 On Tue, 22 May 2012, Steven Rostedt wrote: > On Tue, 2012-05-22 at 18:40 +0200, Thomas Gleixner wrote: > > > > I'm all for benchmarks. But right now, making all readers pass through a > > > single mutex is a huge bottle neck for a lot of loads. Yes, they are > > > mostly Java loads, but for some strange reason, our customers seems to > > > like to run Java on our RT kernel :-p > > > > I'm well aware that mmap_sem is a PITA but replacing one nightmare > > with the next one is not the best approach. > > Perhaps we could just change the mmap_sem to use this approach. Create a > new type of rwsem/lock for -rt that we can be picky about. > > Yeah, mmap_sem is a real PITA and it would be nice to have a solution > that can be used until we can convert it to an RCU lock. That still wants to be verified with numbers on a machine with at least 32 cores and workloads which are mmap heavy. And before we don't have such numbers we can really stop arguing about that solution. Thanks, tglx -- 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/