From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031257AbXDZPSs (ORCPT ); Thu, 26 Apr 2007 11:18:48 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031259AbXDZPSs (ORCPT ); Thu, 26 Apr 2007 11:18:48 -0400 Received: from holomorphy.com ([66.93.40.71]:60839 "EHLO holomorphy.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031257AbXDZPSr (ORCPT ); Thu, 26 Apr 2007 11:18:47 -0400 Date: Thu, 26 Apr 2007 08:19:03 -0700 From: William Lee Irwin III To: Nick Piggin Cc: Andy Whitcroft , Christoph Lameter , "Eric W. Biederman" , linux-kernel@vger.kernel.org, Mel Gorman , David Chinner , Jens Axboe , Badari Pulavarty , Maxim Levitsky Subject: Re: [00/17] Large Blocksize Support V3 Message-ID: <20070426151903.GI19966@holomorphy.com> References: <46303A98.9000605@yahoo.com.au> <46304C74.9040304@yahoo.com.au> <46305177.7060102@yahoo.com.au> <463057D9.9030804@yahoo.com.au> <46309D16.70109@shadowen.org> <4630C061.10309@yahoo.com.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4630C061.10309@yahoo.com.au> Organization: The Domain of Holomorphy User-Agent: Mutt/1.5.13 (2006-08-11) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Andy Whitcroft wrote: >> To my knowledge, moving to a higher base page size has its advantages in >> TLB reach, but brings with it some pretty serious downsides. Especially >> in caching small files. Internal fragmentation in the page cache >> significantly affecting system performance. So much so that development >> is ongoing to see if supporting sub-base-page objects in the buffer >> cache could be beneficial. On Fri, Apr 27, 2007 at 01:08:17AM +1000, Nick Piggin wrote: > I think 16K would be pretty reasonable (ia64 tends to use it). I guess > powerpc went to 64k either because that's what databases want or because > their TLB refills are too slow, so the internal fragmentation bites > them a lot harder. > But that was more of a side comment, because I still think io controllers > should be easily capable of operation on 4K pages. Graphics cards are, > aren't they? Base page size need only be a power-of-two multiple of the MMU pagesize. ISTR the 64KB PAGE_SIZE in ppc64 being motivated by TLB considerations. There is not going to be a way to improve how well IO controllers deal with 4K pages. The scatter/gather lists for smaller fragments will require more device communication overhead no matter what, and furthermore, the more discontiguity, the more seekiness. -- wli