"Michael S. Tsirkin" <m...@redhat.com> writes: > On Thu, Feb 21, 2013 at 08:54:44PM +0800, Liu Ping Fan wrote: >> This is a emulation to virtio-blk dataplane, which push the data >> handling out of biglock. And it is a try to implement this process >> in userspace, while vhost-net in kernel. > > What's the motivation for doing this?
I haven't looked carefully at the patches, but I don't think we should "cheat" when it comes to virtio-net. I think it's useful to have a baseline proof of concept but I think we should focus on making the network layer re-entrant. In terms of why even bother, if we can make virtio-net a viable alternative to vhost-net, it's a huge win. Being in userspace is a huge advantage. I understand the challenges with zero-copy but we really need a proper userspace implementation to determine how much it really matters. Zero-copy tap is also not entirely outside the realm of possibility. >> The iperf's result show it improving the perfermance of base line, >> but still slower than vhost-net (maybe the rx path need optimized). >> >> Todo: >> implement fine lock for net-subsystem > > vhost-net is currently the only way to get zero copy transmit > on linux (and zero copy receive in the future) > so at least in theory it'll always be faster. It might always be faster. But that doesn't mean we should limit the performance of virtio-net in userspace. Some people may be willing to take a small performance hit in order to obtain the security offered by being in userspace. Regards, Anthony Liguori > >> Liu Ping Fan (9): >> vring: split the modification and publish of used ring >> vring: introduce vring_restore() to restore from img >> event poll: make epoll work for normal fd >> event poll: pass event type to event callback >> event poll: enable event poll handle more than one event each time >> virtio net: introduce dataplane for virtio net >> tap: make tap peer work on dedicated data-plane thread >> virtio net: enable dataplane for virtio net >> configure: make virtio net dataplane configurable >> >> configure | 12 ++ >> hw/dataplane/Makefile.objs | 4 +- >> hw/dataplane/event-poll.c | 69 +++++-- >> hw/dataplane/event-poll.h | 14 ++- >> hw/dataplane/virtio-blk.c | 8 +- >> hw/dataplane/virtio-net.c | 444 >> ++++++++++++++++++++++++++++++++++++++++++++ >> hw/dataplane/virtio-net.h | 32 ++++ >> hw/dataplane/vring.c | 37 ++++ >> hw/dataplane/vring.h | 3 + >> hw/virtio-net.c | 94 +++++----- >> hw/virtio-net.h | 64 +++++++ >> hw/virtio-pci.c | 2 +- >> include/net/tap.h | 6 + >> net/tap.c | 92 +++++++++- >> 14 files changed, 806 insertions(+), 75 deletions(-) >> create mode 100644 hw/dataplane/virtio-net.c >> create mode 100644 hw/dataplane/virtio-net.h >> >> -- >> 1.7.4.4 >>
