[Bug 210780] Re: MTRRs set up incorrectly with 4GB RAM -> X slow

pittipatti pittipatti at web.de
Sat Dec 13 13:02:02 UTC 2008


Hi Lean,

I'm using the same hardware as the original poster Mika (Samsung Q45,
Intel GM965 graphics, 4GB ram) and cannot confirm MTTR's beeing setup
correctly in 2.6.27-9-server.

I'm using the server kernel image as the generic kernel only detects
3GB of ram, but that's a different issue.

With 2.6.27-9 the MTTRs are set up like this:

reg00: base=0xc0000000 (3072MB), size=1024MB: uncachable, count=1
reg01: base=0x00000000 (   0MB), size=4096MB: write-back, count=1
reg02: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
reg03: base=0xbf700000 (3063MB), size=   1MB: uncachable, count=1
reg04: base=0xbf800000 (3064MB), size=   8MB: uncachable, count=1


After applying the changes proposed by the tool mttr-uncover from D. Hugh Redelmeier I get the following layout which allows the X-server to enable write-combining:

reg00: base=0x00000000 (   0MB), size=2048MB: write-back, count=1
reg01: base=0x80000000 (2048MB), size=1024MB: write-back, count=1
reg02: base=0x100000000 (4096MB), size=1024MB: write-back, count=1
reg03: base=0xbf700000 (3063MB), size=   1MB: uncachable, count=1
reg04: base=0xbf800000 (3064MB), size=   8MB: uncachable, count=1
reg05: base=0xd0000000 (3328MB), size= 256MB: write-combining, count=1

Is there anything I can test/help to resolve this issue?

-- 
MTRRs set up incorrectly with 4GB RAM -> X slow
https://bugs.launchpad.net/bugs/210780
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