Mapping the frame buffer with WC (Write Combined) memory type, can in practice cause
some memory transactions to be rate-limited at a fraction of the memory frame buffer
write rate. WC allows one core to queue up many globally visible write transactions.
Some unrelated transactions may end up having to wait for all the queued up PCI writes
to be flushed.
The solution is to map the frame buffer as uncachable which prevents the queueing of
more than one PCI write.
Submitted by: Marc De La Gueronniere <email@example.com>
MFC after: 1 week
Sponsored by: Verisign, Inc.