From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S935390AbXGLQgA (ORCPT ); Thu, 12 Jul 2007 12:36:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765718AbXGLQfR (ORCPT ); Thu, 12 Jul 2007 12:35:17 -0400 Received: from e3.ny.us.ibm.com ([32.97.182.143]:46945 "EHLO e3.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1764545AbXGLQfO (ORCPT ); Thu, 12 Jul 2007 12:35:14 -0400 Subject: Re: RFC: CONFIG_PAGE_SHIFT (aka software PAGE_SIZE) From: Dave Hansen To: Andrea Arcangeli Cc: David Chinner , linux-kernel@vger.kernel.org, David Kleikamp In-Reply-To: <20070712163123.GL28613@v2.random> References: <20070706222651.GG5777@v2.random> <20070708232031.GF12413810@sgi.com> <20070710101148.GJ1482@v2.random> <20070712001256.GI31489@sgi.com> <20070712111436.GG28613@v2.random> <20070712144449.GZ31489@sgi.com> <20070712163123.GL28613@v2.random> Content-Type: text/plain Date: Thu, 12 Jul 2007 09:34:57 -0700 Message-Id: <1184258097.26210.75.camel@localhost> Mime-Version: 1.0 X-Mailer: Evolution 2.10.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2007-07-12 at 18:31 +0200, Andrea Arcangeli wrote: > On Fri, Jul 13, 2007 at 12:44:49AM +1000, David Chinner wrote: > > That's crap. Just because a machine has lots of memory does not > > make it OK to waste lots of memory. > > It's not just wasted, it lowers overhead all over the place. Yes, the > benefit of wasting less pagecache may largely outweight the benefit of > having a larger page size, but if you've a lot of memory perhaps your > working set already fits in the cache, or perhaps you don't fit in the > cache regardless of the page size. Have you guys seen Shaggy's page cache tails? http://kernel.org/pub/linux/kernel/people/shaggy/OLS-2006/kleikamp.pdf We've had the same memory waste issue on ppc64 with 64k hardware pages. -- Dave