On Tue, Nov 15, 2005 at 10:23:40AM +0000, Keir Fraser wrote:
> Not expensive in time, but it does waste memory if it's unused.
> Currently we allocate a 64MB aperture if the machine has memory mapped 
> above 2GB (this catches devices like aacraid that can only address 31 
> bits). I could also allocate an aperture of, say, 2MB for smaller 
> systems. There is of course a tension between not wasting memory yet 
> having a big enough aperture that the system will not run out of iommu 
> space and crash even when stressed.
Since Andi's ZONE_DMA32 patches went in last night, how about
foregoing the up-front allocation of bounce buffers and allocating
them as necessary from ZONE_DMA32? once we have that, we should be
able to switch to swiotlb by default.
Cheers,
Muli
-- 
Muli Ben-Yehuda
http://www.mulix.org | http://mulix.livejournal.com/
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