Re: [Qemu-devel] [PATCH v3 0/5] Add netmap backend offloadings support

[Stefan Hajnoczi]

On Mon, Jan 20, 2014 at 06:07:00PM +0100, Vincenzo Maffione wrote:
> The purpose of this patch series is to add offloadings support
> (TSO/UFO/CSUM) to the netmap network backend, and make it possible
> for the paravirtual network frontends (virtio-net and vmxnet3) to
> use it.
> In order to achieve this, these patches extend the existing
> net.h interface to add abstract operations through which a network
> frontend can manipulate backend offloading features, instead of
> directly calling TAP-specific functions.
> 
> Guest-to-guest performance before this patches for virtio-net + netmap:
> 
>     TCP_STREAM                  5.0 Gbps
>     TCP_RR                      12.7 Gbps
>     UDP_STREAM (64-bytes)       790 Kpps
> 
> Guest-to-guest performance after this patches for virtio-net + netmap:
> 
>     TCP_STREAM                  21.4 Gbps
>     TCP_RR                      12.7 Gbps
>     UDP_STREAM (64-bytes)       790 Kpps
> 
> Experiment details:
>     - Processor: Intel i7-3770K CPU @ 3.50GHz (8 cores)
>     - Memory @ 1333 MHz
>     - Host O.S.: Archlinux with Linux 3.11
>     - Guest O.S.: Archlinux with Linux 3.11
> 
>     - QEMU command line:
>         qemu-system-x86_64 archdisk.qcow -snapshot -enable-kvm -device 
> virtio-net-pci,ioeventfd=on,mac=00:AA:BB:CC:DD:01,netdev=mynet -netdev 
> netmap,ifname=vale0:01,id=mynet -smp 2 -vga std -m 3G
> 
> 
> ******** Changes against the previous version ***********
> NOTE: Now the VALE switch supports the offloadings, meaning that TCP/UDP will 
> work
>       even between a virtio-net guest with offloadings enabled and another
>       guest with offloadings disabled. This has been achieved without 
> performance loss
>       on the "fast" case (e.g. two virtio-net-guest communicating with 
> offloadings on).
> 
> (1) removed the second commit of the previous version, which was
>     intended to remove tap_using_vnet_hdr()
> (2) the last commit has been revised: NETMAP_BDG_OFFSET becomes
>     NETMAP_BDG_VNET_HDR, netmap_set_offload() implemented and
>     netmap_has_vnet_hdr_len() rewritten.
> 
> 
> Vincenzo Maffione (5):
>   net: change vnet-hdr TAP prototypes
>   net: extend NetClientInfo for offloading
>   net: TAP uses NetClientInfo offloading callbacks
>   net: virtio-net and vmxnet3 use offloading API
>   net: add offloading support to netmap backend
> 
>  hw/net/virtio-net.c | 16 +++++--------
>  hw/net/vmxnet3.c    | 12 ++++------
>  include/net/net.h   | 19 +++++++++++++++
>  include/net/tap.h   |  4 ++--
>  net/net.c           | 55 +++++++++++++++++++++++++++++++++++++++++++
>  net/netmap.c        | 68 
> ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  net/tap-win32.c     |  8 +++----
>  net/tap.c           | 12 +++++++---
>  8 files changed, 167 insertions(+), 27 deletions(-)

Look good but we should finish by making tap_*() static and adding the
missing function pointer assignments in tap-win32.c.