Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762094AbXEKQxS (ORCPT ); Fri, 11 May 2007 12:53:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755384AbXEKQxM (ORCPT ); Fri, 11 May 2007 12:53:12 -0400 Received: from gw1.cosmosbay.com ([86.65.150.130]:34978 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755051AbXEKQxL (ORCPT ); Fri, 11 May 2007 12:53:11 -0400 Message-ID: <46449F61.2060004@cosmosbay.com> Date: Fri, 11 May 2007 18:52:49 +0200 From: Eric Dumazet User-Agent: Thunderbird 1.5.0.10 (Windows/20070221) MIME-Version: 1.0 To: Ingo Molnar CC: Peter Zijlstra , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Oleg Nesterov , Andrew Morton , Thomas Gleixner , Nick Piggin Subject: Re: [PATCH 0/2] convert mmap_sem to a scalable rw_mutex References: <20070511131541.992688403@chello.nl> <20070511155621.GA13150@elte.hu> In-Reply-To: <20070511155621.GA13150@elte.hu> 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]); Fri, 11 May 2007 18:52:54 +0200 (CEST) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1214 Lines: 37 Ingo Molnar a ?crit : > * 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). >> >> 2-way x86_64 pentium D box: >> >> 2.6.21 >> >> /usr/bin/time ./ebizzy -m -P >> 59.49user 137.74system 1:49.22elapsed 180%CPU (0avgtext+0avgdata 0maxresident)k >> 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps >> >> 2.6.21-rw_mutex >> >> /usr/bin/time ./ebizzy -m -P >> 57.85user 124.30system 1:42.99elapsed 176%CPU (0avgtext+0avgdata 0maxresident)k >> 0inputs+0outputs (0major+33555877minor)pagefaults 0swaps > > nice! This 6% runtime reduction on a 2-way box will i suspect get > exponentially better on systems with more CPUs/cores. As long you only have readers, yes. But I personally find this new rw_mutex not scalable at all if you have some writers around. percpu_counter_sum is just a L1 cache eater, and O(NR_CPUS) - 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/