Re: [PATCH] x86: create array based interface to change page attribute
From: Arjan van de Ven
Date: Mon Mar 31 2008 - 12:10:41 EST
Thomas Hellström wrote:
Let me rehprase. Not really time-critical but it is of some importance
that CPA is done quickly.
We're dealing with the tradeoff of reading from uncached device memory
uncached or write combining ?
vs taking the pages out of
AGP, setting up a cache-coherent mapping, read and then change back.
What we'd really would like to set up is a pool of completely unmapped
(like highmem) pages. Then we could, to a large extent, avoid the CPA
calls.
changing attributes by nature means a tlb flush and a bunch of expensive cache work.
That's never going to be cheap, I guess it all depends on how much work you do
on the memory for it to pay off or not...
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