From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758257AbYEDUX1 (ORCPT ); Sun, 4 May 2008 16:23:27 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756153AbYEDUXT (ORCPT ); Sun, 4 May 2008 16:23:19 -0400 Received: from rv-out-0506.google.com ([209.85.198.229]:24691 "EHLO rv-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756563AbYEDUXR (ORCPT ); Sun, 4 May 2008 16:23:17 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Msy3fswJsQrZIflPXXB4hVO73Ise01F4ql7nSyL5YnGfjW7XevzwY2IcR6+dU/YYtkGgZAI0DbGuMjRrVAGJrEYeUnOfk3Y4L6foy1m2MWC+zn4RY2QgCLsq/T7zhn8DslZvz6AURvZRC/yNLQvPb/wbX1kXsONeR2EsgcVe1mw= Message-ID: <86802c440805041323s1484a8ecx5dbe639d658d015b@mail.gmail.com> Date: Sun, 4 May 2008 13:23:17 -0700 From: "Yinghai Lu" To: "Frans Pop" Subject: Re: [git head] Should X86_PAT really default to yes? Cc: "Jesse Barnes" , "Pallipadi, Venkatesh" , linux-kernel@vger.kernel.org, "Ingo Molnar" , "Packard, Keith" In-Reply-To: <200805040910.57088.elendil@planet.nl> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <200805022122.03576.elendil@planet.nl> <924EFEDD5F540B4284297C4DC59F3DEEFB8D3D@orsmsx423.amr.corp.intel.com> <200805021340.24987.jesse.barnes@intel.com> <200805040910.57088.elendil@planet.nl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 4, 2008 at 12:10 AM, Frans Pop wrote: > On Friday 02 May 2008, Jesse Barnes wrote: > > This is just a transient issue during VT switch or server exit though, > > right? X functionality isn't affected, and your VTs work fine? > > Transient only. I've just tested again and this time the band > was visible on top of the text on VT1 for about 2 seconds. Then it > disappeared. > The artifacts also appear when I log out from KDE (i.e. without exiting the > server), and I also get the messages when logging out and logging in again. > > I do not see any performance issues, but I've only used this kernel for a > very short time. > > > > If so, it might not be a PAT issue but just a different memory layout or > > something (and therefore it would really just be a cosmetic bug in the X > > driver). > > The artifacts may not be a PAT issue directly, but it is a clear regression > for me as I currently have a nice clean screen when X shuts down. I'm also > 100% sure that it is caused by enabling PAT. A kernel with same config and > only PAT disabled does not show the artifacts. > > Would you like me to file a bug against X for these artifacts? > If so, against what component? The i810 driver or the server? > > > On Saturday 03 May 2008, Jesse Barnes wrote: > > > I don't see these error messages on my 965 here. May be I have different > > > x version. > > > Hm, yeah that could be. strace would tell us. > > Would you like me to do an strace? > > Attached my Xorg log for basic info (versions are current Debian unstable) > and the config I used. > > Also attached a dmesg that shows the messages. As you can see there are some > repeats. > - first 22 "expected mapping type" when X is started > - second 22 "expected mapping type" when logging in > - 9 "freeing invalid memtype" when logging out > - 22 "expected mapping type" when logging in again > - 9 "freeing invalid memtype" when logging out again > - last series "expected mapping type" when restarting X server > > > > On Saturday 03 May 2008, Jesse Barnes wrote: > > More recent versions of X will use sysfs rather than /dev/mem (though > > we're still using the mprotect hack there to give us UC-), so yeah this > > warning should already be gone in more recent builds. > > On Friday 02 May 2008, Pallipadi, Venkatesh wrote: > > ... and should not cause any side-effects other than little annoyance. > > > On Friday 02 May 2008, Jesse Barnes wrote: > > I really think PAT should be on by default; if you're running into real > > functional or performance problems we'd better get them fixed rather than > > disabling PAT... > > I must say that I'm fairly disappointed by your (plural) attitude to these > regressions, especially given that you both seem to feel it is important > that people will actually use PAT. > > I would say that 40+ messages each time I start X is more than "a little > annoyance", especially if you run logcheck (as I do). > > I also think you both seriously underestimate how it will impact enabling > PAT, especially by distributions. Although the errors and the artifacts may > be minor from a technical point of view, they are the sort of issues that > users file bug reports about. Loads of them! > So I expect distros will be extremely reluctant to enable PAT when they know > they can expect this. The fact that the messages will go away at some point > in the future is absolutely not relevant. > > Add to that the current warning in the Kconfig help: > Say N here if you see bootup problems (boot crash, boot hang, > spontaneous reboots) or a non-working video driver. > > Do you really think that distros can afford the risk of such issues in their > generic kernel images even if it would only affect a small minority of > their user base? If this warning is realistic then IMHO X86_PAT should > default to N and be marked "experimental". > > You can be sure that I at least will not be enabling X86_PAT in the near > future because of these two issues. And given the nature of this option I'm > quite likely to completely forget about it afterwards... > > > That said, I'll be happy to help trace and get these issues fixed. can you boot with pat=off and send out /proc/mtrr? YH