Re: [Xen-devel] USB virt status --- Help please!!!

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 14 Nov 2005, at 17:30, Stephen C. Tweedie wrote:

> Having swiotlb the default would also have dealt with the network DMA
> problem we had recently, with pci_map_single() refusing to work over
> page boundaries.
>
> That got fixed that by adding an arch-specific __alloc_skb which 
> avoided
> crossing page boundaries by disabling CONFIG_DEBUG_SLAB for the skb
> caches.  But that fix is also something that I doubt maintainers will
> allow to go upstream.  I wonder if we'll find enough such special cases
> that we really want to have a swiotlb available, just in case, at all
> times?
swiotlb performance is pretty poor since it involves memcpy. The 
alloc_skb fix was pretty clean, if we're allowed an arch hook for 
alloc_skb. We didn;t need to hack the slab allocator itself.
 -- Keir


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel