Re: [Xen-devel] Any work on sharing of large multi-page segments?

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 17.03.15 at 01:46, <andreww591@xxxxxxxxx> wrote:
> On 3/16/15, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>> So where do you expect the major performance / scalability
>> improvement to be gained? Internally to Xen, each page will need
>> to be tracked separately anyway, as what appears physically
>> contiguous in the granting guest may (and likely will) not be
>> contiguous in machine memory (i.e. from Xen's perspective).
>> Furthermore the public interface is currently written such that
>> grant lengths must be less than 64k. I.e. already at the very
>> simple first steps you'd be faced with implementing bigger length
>> counterparts of (almost) all existing interfaces.
> 
> Since I'm looking to grant OpenGL buffers that can be many megabytes
> in size, I would think there would be a fair bit of overhead if the
> backend domain had to make a hypercall to map every single page of a
> buffer. I guess what I could do would be to add a hypercall that maps
> a contiguous group of grant entries (contiguous in the grant table,
> not necessarily contiguous in memory).

And how would that be significantly different from the batching
that's already built into the grant table hypercall?

Jan


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