Re: [Qemu-devel] [QA-virtio]:Why vring size is limited to 1024?

[Avi Kivity]

On 10/08/2014 01:55 PM, Michael S. Tsirkin wrote:
> > Inline descriptors will amortize the cache miss over 4 descriptors, and will
> > allow the hardware to prefetch, since the descriptors are linear in memory.
> If descriptors are used in order (as they are with current qemu)
> then aren't they amortized already?

The descriptors are only in-order for non-zero-copy net.  They are out 
of order for block and zero-copy net.

(also, the guest has to be careful in how it allocates descriptors).