I'm running X + DRI2 + KMS on i915 hardware (intel HD4500, actually) and I'm getting the following message in dmesg:
After some googling, It seems that I need an MTRR entry for video memory in write-combining mode, which I don't have according to /proc/mtrr.
mtrr: type mismatch for e0000000,10000000 old: write-back new: write-combining
[drm] MTRR allocation failed. Graphics performance may suffer.
It seems this problem happens because of my 4GB RAM and maybe x86_64.
reg00: base=0x000000000 ( 0MB), size=32768MB, count=1: write-back
reg01: base=0x0e0000000 ( 3584MB), size= 512MB, count=1: uncachable
reg02: base=0x0ddc00000 ( 3548MB), size= 4MB, count=1: uncachable
reg03: base=0x0de000000 ( 3552MB), size= 32MB, count=1: uncachable
It might be a kernel issue, so I tried the following options, as some users suggested:
That didn't fix it.
But now I remember that some work about DRI2 was about moving from static to dynamic memory management (GEM objects).
So, is this somehow related to the DRI2 transition? Or any ideas about how to fix that?