From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751276AbWGHBZo (ORCPT ); Fri, 7 Jul 2006 21:25:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751286AbWGHBZn (ORCPT ); Fri, 7 Jul 2006 21:25:43 -0400 Received: from omx1-ext.sgi.com ([192.48.179.11]:14553 "EHLO omx1.americas.sgi.com") by vger.kernel.org with ESMTP id S1751276AbWGHBZn (ORCPT ); Fri, 7 Jul 2006 21:25:43 -0400 Date: Fri, 7 Jul 2006 18:25:22 -0700 (PDT) From: Christoph Lameter To: Andi Kleen cc: linux-kernel@vger.kernel.org, Martin Bligh , Christoph Hellwig , Marcelo Tosatti , Arjan van de Ven , Nick Piggin , KAMEZAWA Hiroyuki Subject: Re: [RFC 5/8] x86_64 without ZONE_DMA In-Reply-To: <200607080300.16931.ak@suse.de> Message-ID: References: <20060708000501.3829.25578.sendpatchset@schroedinger.engr.sgi.com> <200607080220.39100.ak@suse.de> <200607080300.16931.ak@suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Sat, 8 Jul 2006, Andi Kleen wrote: > > The savings are not only from the code paths. The VM itself is cleaner and > > the balancing issues are not that troublesome anymore. > > Doesn't help - it has to be fixed anyways for NUMA and other architectures. Some architectures like ours can run with a single zone since they have DMA that works anywhere. Same thing is true for my machines are home and at work. > Also in my experience empty zones are not a significant problem for VM > balancing. The problem is that the zones are not even empty! We keep 16M in some weird ZONE_DMA that barely anyone one uses anymore and add slabs to it that are only used by some confused device drivers. Also the empty zones are still a problem since they have to be scanned repeatedly (potentially on each allocation). They waste cachelines and result in loops where we could just have straight code.