Large mmio resources and 4G+ of RAM...

Eric W. Biederman ebiederman at
Tue Jun 1 00:42:01 CEST 2004

For the longest time I have been fighting what to do with machines
that have 4GB or more of memory and large memory mapped I/O resources.
As the conflict in memory space can cause a loss of 1/2GB of memory.
Which does not tend to be good for performance.

Looking the large memory mapped I/O resources all have 64bit BARs.  So
I am just going to modify the LinuxBIOS resource allocator to put
64bit BARs on x86-64 boxes at least above the top of memory.

There are a couple of short term hacks that I can do with relocating
memory but on the Opteron the more memory I add the more problems
I run into.  And moving BARS above 4G looks like the right term

Any objections?


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