Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758891AbXELP1L (ORCPT ); Sat, 12 May 2007 11:27:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754672AbXELP06 (ORCPT ); Sat, 12 May 2007 11:26:58 -0400 Received: from gw1.cosmosbay.com ([86.65.150.130]:36191 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754017AbXELP06 (ORCPT ); Sat, 12 May 2007 11:26:58 -0400 Message-ID: <4645DCA2.80408@cosmosbay.com> Date: Sat, 12 May 2007 17:26:26 +0200 From: Eric Dumazet User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Esben Nielsen CC: Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Andrew Morton , Ingo Molnar , Thomas Gleixner , Nick Piggin Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex References: <20070511131541.992688403@chello.nl> <1178964103.6810.55.camel@twins> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [86.65.150.130]); Sat, 12 May 2007 17:26:34 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1132 Lines: 35 Esben Nielsen a ?crit : > > > On Sat, 12 May 2007, Peter Zijlstra wrote: > >> On Sat, 2007-05-12 at 11:27 +0200, Esben Nielsen wrote: >>> >>> On Fri, 11 May 2007, Peter Zijlstra wrote: >>> >>>> >>>> I was toying with a scalable rw_mutex and found that it gives ~10% >>>> reduction in >>>> system time on ebizzy runs (without the MADV_FREE patch). >>>> >>> >>> You break priority enheritance on user space futexes! :-( >>> The problems is that the futex waiter have to take the mmap_sem. And as >>> your rw_mutex isn't PI enabled you get priority inversions :-( >> >> Do note that rwsems have no PI either. >> PI is not a concern for mainline - yet, I do have ideas here though. >> >> > If PI wasn't a concern for mainline, why is PI futexes merged into the > mainline? If you really care about futexes and mmap_sem, just use private futexes, since they dont use mmap_sem at all. - 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/