Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261678AbVBDJa2 (ORCPT ); Fri, 4 Feb 2005 04:30:28 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261292AbVBDJa1 (ORCPT ); Fri, 4 Feb 2005 04:30:27 -0500 Received: from mail.suse.de ([195.135.220.2]:2008 "EHLO Cantor.suse.de") by vger.kernel.org with ESMTP id S263601AbVBDJ2R (ORCPT ); Fri, 4 Feb 2005 04:28:17 -0500 Date: Fri, 4 Feb 2005 10:28:01 +0100 From: Andi Kleen To: Paul Mackerras Cc: Christoph Lameter , Rik van Riel , Marcelo Tosatti , David Woodhouse , linux-mm@kvack.org, linux-kernel@vger.kernel.org, akpm@osdl.org Subject: Re: A scrub daemon (prezeroing) Message-ID: <20050204092801.GE10347@wotan.suse.de> References: <1106828124.19262.45.camel@hades.cambridge.redhat.com> <20050202153256.GA19615@logos.cnet> <20050202163110.GB23132@logos.cnet> <16898.46622.108835.631425@cargo.ozlabs.ibm.com> <16899.2175.599702.827882@cargo.ozlabs.ibm.com> <16899.15980.791820.132469@cargo.ozlabs.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <16899.15980.791820.132469@cargo.ozlabs.ibm.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 870 Lines: 18 > > advantage of all the optimizations that modern memory subsystems have for > > linear accesses. And if hardware exists that can offload that from the cpu > > then the cpu caches are only minimally affected. > > I can believe that prezeroing could provide a benefit on some > machines, but I don't think it will provide any on ppc64. On modern x86 clears can be done quite quickly (no memory read access) with write combining writes. The problem is just that this will force the page out of cache. If there is any chance that the CPU will be accessing the data soon it's better to do the slower cached RMW clear. -Andi - 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/