From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031232AbXDZOsQ (ORCPT ); Thu, 26 Apr 2007 10:48:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031233AbXDZOsQ (ORCPT ); Thu, 26 Apr 2007 10:48:16 -0400 Received: from smtp109.mail.mud.yahoo.com ([209.191.85.219]:32585 "HELO smtp109.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1031232AbXDZOsP (ORCPT ); Thu, 26 Apr 2007 10:48:15 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:X-YMail-OSG:Message-ID:Date:From:User-Agent:X-Accept-Language:MIME-Version:To:CC:Subject:References:In-Reply-To:Content-Type:Content-Transfer-Encoding; b=KYFu3FZ4R9smg108qV5DKqL/ovnU6Ok7MqzE7vAMxj+HqwoKkhsEBeWqt4N1Ug7o7UXAjGRJmyv+rUKB3AXIrMymf7e2+crH0xjkEXGY8tNcAC8m68SqY0F0HjOcahaWNgiVDdd2EkOLs138uls7Aedmu7USsJRdwoYidQ+Rbn8= ; X-YMail-OSG: d3qmOY4VM1mGfwF8yKSnjLK6mHWg1XLEBYepBbeGwgCLfyYlG2Rcrnjye4hxdLKPBZNYLzae3Q-- Message-ID: <4630BB95.80209@yahoo.com.au> Date: Fri, 27 Apr 2007 00:47:49 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.12) Gecko/20051007 Debian/1.7.12-1 X-Accept-Language: en MIME-Version: 1.0 To: Mel Gorman CC: Christoph Lameter , "Eric W. Biederman" , linux-kernel@vger.kernel.org, William Lee Irwin III , David Chinner , Jens Axboe , Badari Pulavarty , Maxim Levitsky Subject: Re: [00/17] Large Blocksize Support V3 References: <20070424222105.883597089@sgi.com> <463048FE.5000600@yahoo.com.au> <20070426100652.GB27620@skynet.ie> In-Reply-To: <20070426100652.GB27620@skynet.ie> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mel Gorman wrote: > On (25/04/07 23:46), Christoph Lameter didst pronounce: > >>On Thu, 26 Apr 2007, Nick Piggin wrote: >> >> >>>Yeah. IMO anti-fragmentation and defragmentation is the hack, and we >>>should stay away from higher order allocations whenever possible. >> >>Right and we need to create series of other approaches that we then label >>"non-hack" to replace it. >> > > > To date, there hasn't been a credible alternative to dealing with > fragmentation. Breaking the 1:1 virtual:physical mapping and defragmenting > would incur a serious performance hit. Depends what you mean by "dealing with", I guess. I would say there has been no credible alternative to virtually mapping the kernel. >>>Hardware is built to handle many small pages efficintly, and I don't >>>understand how it could be an SGI-only issue. Sure, you may have an >>>order of magnitude or more memory than anyone else, but even my lowly >>>desktop _already_ has orders of magnitude more pages than it has TLB >>>entries or cache -- if a workload is cache-nice for me, it probably >>>will be on a 1TB machine as well, and if it is bad for the 1TB machine, >>>it is also bad on mine. >> >>There have been numbers of people that have argued the same point. Just >>because we have developed a way of thinking to defend our traditional 4k >>values does not make them right. >> >> >>>If this is instead an issue of io path or reclaim efficiency, then it >>>would be really nice to see numbers... but I don't think making these >>>fundamental paths more complex and slower is a nice way to fix it >>>(larger PAGE_SIZE would be, though). >> >>The code paths can stay the same. You can switch CONFIG_LARGE pages off >>if you do not want it and it is as it was. >> > > > It may not even need that that much effort. The most stressful use of the > high order allocation paths here require the creation of a filesystem and > is a deliberate action by the user. Saying "oh this stuff may not always work quite right for everyone, but it is OK because it is a special purpose solution for now" IMO is a big sign saying that it is a bad design, and including it means we're lumped with it forever. -- SUSE Labs, Novell Inc.