On Fri, Jun 13, 2014 at 10:10 PM, Paolo Bonzini <pbonz...@redhat.com> wrote: > Il 13/06/2014 15:41, Vincent JARDIN ha scritto: >> I do repeat this use case that you had removed because vhost-user does >> not solve it yet: >> >>>> - ivshmem -> framework to be generic to have shared memory for many >>>> use cases (HPC, in-memory-database, a network too like memnic). > > > Right, ivshmem is better for guest-to-guest. vhost-user is not restricted > to networking, but it is indeed more focused on guest-to-host. ivshmem is > usable for guest-to-host, but I would prefer still some "hybrid" that uses > vhost-like messages to pass the shared memory fds to the external program.
ivshmem has a performance disadvantage for guest-to-host communication. Since the shared memory is exposed as PCI BARs, the guest has to memcpy into the shared memory. vhost-user can access guest memory directly and avoid the copy inside the guest. Unless someone steps up and maintains ivshmem, I think it should be deprecated and dropped from QEMU. Stefan
