Messages in this thread | | | From | Segher Boessenkool <> | Subject | Re: [PATCH] ppc32/64: Map prefetchable PCI without guarded bit | Date | Thu, 24 Mar 2005 19:20:43 +0100 |
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> While experimenting with framebuffer access performances, we noticed a > very significant improvement in write access to it when not setting > the "guarded" bit on the MMU mappings. This bit basically says that > reads and writes won't have side effects (it allows speculation).
Unless the data is already in cache.
> It appears that it also disables write combining.
When the page is also cache-inhibited, it indeed does.
Btw, did you ever get to fix the problem with mapping the last page of physical address space via /dev/mem ?
Segher
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