From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964809AbXFGRjP (ORCPT ); Thu, 7 Jun 2007 13:39:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760781AbXFGRjA (ORCPT ); Thu, 7 Jun 2007 13:39:00 -0400 Received: from terminus.zytor.com ([192.83.249.54]:57337 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754470AbXFGRi7 (ORCPT ); Thu, 7 Jun 2007 13:38:59 -0400 Message-ID: <4668412D.3030506@zytor.com> Date: Thu, 07 Jun 2007 10:32:29 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.0 (X11/20070419) MIME-Version: 1.0 To: "Robert P. J. Day" CC: Satyam Sharma , Nick Piggin , Linux Kernel Mailing List , Ralf Baechle Subject: Re: why does the macro "ZERO_PAGE" take an argument? References: <4667EC18.4080904@yahoo.com.au> In-Reply-To: X-Enigmail-Version: 0.95.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Robert P. J. Day wrote: >> The comment above empty_zero_page and zero_page_mask >> declarations at arch/mips/mm/init.c:508 sheds light on this ... > > well, it *sort of* does. at line 64 of that file: > > /* > * We have up to 8 empty zeroed pages so we can map one of the right colour > * when needed. This is necessary only on R4000 / R4400 SC and MC versions > * where we have to avoid VCED / VECI exceptions for good performance at > * any price. Since page is never written to after the initialization we > * don't have to care about aliases on other CPUs. > */ > > although it's not clear where in the source tree are the invocations > that would actually make a difference to a MIPS system, which is why > i've CC'ed ralf on this. i'm sure he can clear this up. :-) x86 could also benefit from coloured zeropages. In fact, I thought it already had them (K8 wants as many as 8.) -hpa