Re: [Qemu-devel] [RFC PATCH RDMA support v4: 03/10] more verbose documentation of the RDMA transport

[Michael S. Tsirkin]

On Tue, Mar 19, 2013 at 06:52:59PM +0100, Paolo Bonzini wrote:
> Il 19/03/2013 18:40, Michael R. Hines ha scritto:
> > registration scheme would not work with cgroups because we would be 
> > attempting to pin zero pages (for no reason) that cgroups has already
> > kicked out, which would defeat the purpose of using cgroups.
> 
> Yeah, pinning would be a problem.
> 
> > So, if I submit a separate patch to fix this, would you guys review it?
> > (Using /dev/pagemap).
> 
> Sorry about the ignorance, but what is /dev/pagemap? :)
> 
> > Unless there is a better idea? Does KVM expose the necessary mappings?
> 
> We could have the balloon driver track the pages.  I and Michael had
> some initial work a few months ago on extending the virtio-balloon spec
> to allow this.  It went nowhere, though.
> 
> Still, at this point this is again an RDMA-specific problem, I don't
> think it would be that bad if the first iterations of RDMA didn't
> support ballooning/overcommit.
> 
> Paolo

My problem is with the protocol. If it assumes at the protocol level
that everything is pinned down on the destination, we'll have to rework
it all to make it really useful.

-- 
MST