From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263246AbTEPWtq (ORCPT ); Fri, 16 May 2003 18:49:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263281AbTEPWtq (ORCPT ); Fri, 16 May 2003 18:49:46 -0400 Received: from ebiederm.dsl.xmission.com ([166.70.28.69]:47448 "EHLO frodo.biederman.org") by vger.kernel.org with ESMTP id S263246AbTEPWtq (ORCPT ); Fri, 16 May 2003 18:49:46 -0400 To: Andi Kleen Cc: kraxel@suse.de, jsimmons@infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] Use MTRRs by default for vesafb on x86-64 References: <20030515145640.GA19152@averell> From: ebiederm@xmission.com (Eric W. Biederman) Date: 16 May 2003 16:58:39 -0600 In-Reply-To: <20030515145640.GA19152@averell> Message-ID: User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.1 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 Andi Kleen writes: > x86-64 cannot call the 32bit VESA BIOS. This means when vesafb is active > it does software copying in the vesa frame buffer. This is insanely slow > when the frame buffer is not marked for write combining. > > Some discussion showed that the use_mtrr flag was only off for some > old broken ET4000 ISA card. x86-64 has no ISA, so this is no concern. > Make the default depend on CONFIG_ISA. > > Patch for 2.5.69. Originally suggested by Gerd Knorr. I don't know if this affects the frame buffers per se. But often BIOS's on systems with large amounts of memory configure overlapping mtrrs (where an uncacheable mtrr would override a larger cacheable range). To date this has confused the linux mtrr code when it tries to modify things, and you cannot properly setup mtrrs. I believe this applies to both the fb case as well as X. Eric