Re: [Qemu-devel] [RFC v2 0/10] Support Receive-Segment-Offload(RSC) for WHQL test of Window guest

[Jason Wang <jasowang@redhat.com>]

On 02/01/2016 02:13 AM, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
>
> Patch v2 add detailed commit log.
>
> This patch is to support WHQL test for Windows guest, while this feature also
> benifits other guest works as a kernel 'gro' like feature with userspace implementation.
> Feature information:
>   http://msdn.microsoft.com/en-us/library/windows/hardware/jj853324
>
> Both IPv4 and IPv6 are supported, though performance with userspace virtio
> is slow than vhost-net, there is about 30-40 percent performance
> improvement to userspace virtio, this is done by turning this feature on
> and disable 'tso' on corresponding tap interface.

Maybe you can share us with the numbers?

>
> Test steps:
> Although this feature is mainly used for window guest, i used linux guest to help test
> the feature, to make things simple, i used 3 steps to test the patch as i moved on.
> 1. With a tcp socket client/server pair runnig on 2 linux guest, thus i can control
> the traffic and debugging the code as i want.
> 2. Netperf on linux guest test the throughput.
> 3. WHQL test with 2 Windows guest.
>
> Current status:
> IPv4 pass all the above tests. 
> IPv6 just passed test step 1 and 2 as described ahead, the virtio nic cannot receive
> any packet in WHQL test, debugging on the host side shows all the packets have been
> pushed to th vring, by replacing it with a linux guest, i add 10 extra packets before
> sending out the real packet, tcpdump running on guest only capture 6 packets, don't
> find out the root cause yet, will continue working on this.

Maybe you can try dropmonitor [1] in both host and guest to find the
reason of packet dropping.

[1] ./perf script net_dropmonitor
>
> Note:
> A 'MessageDevice' nic chose as 'Realtek' will panic the system sometimes during setup,
> this can be figured out by replacing it with an 'e1000' nic.
>
> Pending issues & Todo list:
> 1. Dup ack count not added in the virtio_net_hdr, but WHQL test case passes,
> looks like a bug in test case.
> 2. Missing a Feature Bit
> 3. Missing a few tcp/ip handling
>     ECN change.
>     TCP window scale.
>
> Wei Xu (10):
>   virtio-net rsc: Data structure, 'Segment', 'Chain' and 'Status'
>   virtio-net rsc: Initilize & Cleanup
>   virtio-net rsc: Chain Lookup, Packet Caching and Framework of IPv4
>   virtio-net rsc: Detailed IPv4 and General TCP data coalescing
>   virtio-net rsc: Create timer to drain the packets from the cache pool
>   virtio-net rsc: IPv4 checksum
>   virtio-net rsc: Checking TCP flag and drain specific connection
>     packets
>   virtio-net rsc: Sanity check & More bypass cases check
>   virtio-net rsc: Add IPv6 support
>   virtio-net rsc: Add Receive Segment Coalesce statistics
>
>  hw/net/virtio-net.c            | 626 ++++++++++++++++++++++++++++++++++++++++-
>  include/hw/virtio/virtio-net.h |   1 +
>  include/hw/virtio/virtio.h     |  65 +++++
>  3 files changed, 691 insertions(+), 1 deletion(-)
>