Messages in this thread | | | Date | Sun, 4 May 2008 13:23:17 -0700 | From | "Yinghai Lu" <> | Subject | Re: [git head] Should X86_PAT really default to yes? |
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On Sun, May 4, 2008 at 12:10 AM, Frans Pop <elendil@planet.nl> 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
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