AW: observations with git X server intel/MTRR/performance

Tobias Hain tobias.hain at
Fri Nov 7 15:56:49 PST 2008

> On Thu, 2008-11-06 at 14:03 +0100, Tobias Hain wrote:
>> Hello,
>> Problem 2: MTRR not being set on intel
>> ==========
>> [...] 
>> And on every exit of the x session:
>> waiting for X server to shut down error setting MTRR (base = 0xe0000000,
>> size = 0x10000000, type = 1) Invalid argument (22)
>> But how to properly fix that? Who exactly is supposed to set up
>> the MTRR registers?

Eric wrote:
> Things that use libpciaccess (the X Server) should be getting correct wc
> mappings thanks to using the resource_wc sysfs file.  If you update your
> kernel, the kernel also gets wc mappings using the new io_map_atomic
> interfaces.  So at that point, the MTRR shouldn't be necessary.

I do see the different interfaces for controlling address space cache

If I use these stock ubuntu 8.10 compoents:
. libpciaccess 0.10.3
. x-server 1.5.2
. xf86-video-intel 2.4.2 (which is labelled 2.4.1 in ubuntu)
I don't get the above MTRR error messages.

But the self compiled
. x-server master or 1.5.3
. xf86-video-intel master or 2.5.0
throw these regardless of 2.6.28-rc2 or 2.6.28-rc3 or your drm-intel-next
branch and regardless of PAT or nopat kernel.

I don't see a performance difference anyway when manually applying a MTRR WC
region so I'm assuming the libpciaccess does the right thing. Still these
MTRR messages are confusing - I don't know which module of the xserver is
thowing them and why. And whether it tries to mess with old fashioned MTRRs
or whether it's just deprecated information logging.


Talking about performance: Going from 2.6.28-rc2 -> rc3 of your
drm-intel-next branch did improve glxgears performance from 800 -> 1000fps
on GM965 @T7500. Wobby windows are noticeable smoother on WUXGA screens now.

Performance didn't go up for me when going classic -> TTM -> GEM. But for
some reason it just did. Good work! Even if that wasn't the focus anyway.


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