From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Sun, 24 Mar 2002 17:55:11 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Sun, 24 Mar 2002 17:55:01 -0500 Received: from userbb201.dsl.pipex.com ([62.190.241.201]:41900 "EHLO irishsea.home.craig-wood.com") by vger.kernel.org with ESMTP id ; Sun, 24 Mar 2002 17:54:45 -0500 Date: Sun, 24 Mar 2002 22:54:01 +0000 From: Nick Craig-Wood To: Andrew Morton Cc: Rogier Wolff , Linus Torvalds , yodaiken@fsmlabs.com, Andi Kleen , Paul Mackerras , linux-kernel@vger.kernel.org Subject: Re: [Lse-tech] Re: 10.31 second kernel compile Message-ID: <20020324225401.A30709@axis.demon.co.uk> In-Reply-To: <200203242112.WAA09406@cave.bitwizard.nl> <3C9E46BD.D0BEEB2A@zip.com.au> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 24, 2002 at 01:35:57PM -0800, Andrew Morton wrote: > Frankly, all the discussion I've seen about altering page sizes > threatens to add considerable complexity for very dubious gains. > The only place where I've seen a solid justification is for > scientific applications which have a huge working set, and need > large pages to save on TLB thrashing. A widely used example is mprime - the mersenne prime finding program ( http://www.mersenne.org/ ). This typically uses 8 or more MBytes of RAM which it completely thrashes. The program is written in very efficient assembler code and has been designed not to thrash the TLB as much as possible, but with a working set of > 8 MBs (which is iterated through many times a second at maximum memory bandwith) large pages would make a real improvement to it. Since each run takes weeks any improvement would be eagerly snatched at by the 1000s of people running this program ;-) If there was some hack where 4MB pages could be allocated for applications like this then I'd be very happy! -- Nick Craig-Wood ncw@axis.demon.co.uk