Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754730Ab0AEPQy (ORCPT ); Tue, 5 Jan 2010 10:16:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753568Ab0AEPQw (ORCPT ); Tue, 5 Jan 2010 10:16:52 -0500 Received: from nlpi157.sbcis.sbc.com ([207.115.36.171]:33110 "EHLO nlpi157.prodigy.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754820Ab0AEPQt (ORCPT ); Tue, 5 Jan 2010 10:16:49 -0500 Date: Tue, 5 Jan 2010 09:14:21 -0600 (CST) From: Christoph Lameter X-X-Sender: cl@router.home To: KAMEZAWA Hiroyuki cc: Linus Torvalds , Minchan Kim , Peter Zijlstra , "Paul E. McKenney" , Peter Zijlstra , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "hugh.dickins" , Nick Piggin , Ingo Molnar Subject: Re: [RFC][PATCH 6/8] mm: handle_speculative_fault() In-Reply-To: <20100105143046.73938ea2.kamezawa.hiroyu@jp.fujitsu.com> Message-ID: References: <20100104182429.833180340@chello.nl> <20100104182813.753545361@chello.nl> <20100105092559.1de8b613.kamezawa.hiroyu@jp.fujitsu.com> <28c262361001042029w4b95f226lf54a3ed6a4291a3b@mail.gmail.com> <20100105134357.4bfb4951.kamezawa.hiroyu@jp.fujitsu.com> <20100105143046.73938ea2.kamezawa.hiroyu@jp.fujitsu.com> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1067 Lines: 21 On Tue, 5 Jan 2010, KAMEZAWA Hiroyuki wrote: > I'd like to hear use cases of really heavy users, too. Christoph ? A typical use case is a highly parallel memory intensive process (simulations f.e.). Those are configured with the number of hardware threads supported in mind to max out the performance of the underlying hardware. On startup they start N threads and then each thread begins initializing its memory (to get proper locality it has to be done this way, you also want concurrency during this expensive operation). The larger the number of threads the more contention on the cachelines containing mmap_sem and the other cacheline containing the rss counters. In extreme cases we had to wait 30mins to an hour in order for the cacheline bouncing to complete (startup of a big HPC app on IA64 with 1k threads). -- 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/