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Re: [Qemu-devel] [ RFC Patch v5 0/2] Support Receive-Segment-Offload(RSC

From: Jason Wang
Subject: Re: [Qemu-devel] [ RFC Patch v5 0/2] Support Receive-Segment-Offload(RSC) for WHQL
Date: Tue, 24 May 2016 16:03:04 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2

On 2016年05月24日 04:14, address@hidden wrote:
From: Wei Xu <address@hidden>

Changes in V5:
- Passed all IPv4/6 test cases
- Add new fields in 'virtio_net_hdr'
- Set 'gso_type' & 'coalesced packets' in new field.
- Bypass all 'tcp option' packet
- Bypass all 'pure ack' packet
- Bypass all 'duplicate ack' packet
- Change 'guest_rsc' feature bit to 'false' by default
- Feedbacks from v4, typo, etc.

Patch does not apply on master ...

There is still a few pending issues about the feature bit, and need to be
discussed with windows driver maintainer, so linux guests with this patch
won't work at current, haven't figure it out yet, but i'm guessing it's
caused by the 'gso_type' is set to 'VIRTIO_NET_HDR_GSO_TCPV4/6',
will fix it after get the final solution, the below test steps and
performance data is based on v4.

Can we split the patches into smaller ones to make review or merging easier? E.g can we send the patches without any feature negotiation and vnet header extension?

We can focus on the coalescing (maybe ipv4) without any guest involvement in this series. In this way, the issues were limited and can be converged soon. After this has been merged, we can add patches that co-operate with guests on top (since it needs agreement on virtio specs). Does this sounds a good plan?

Another suggestion from Jason is to adjust part of the code to make it
more readable, since there maybe still few change about the flowchart
in the future, such as timestamp, duplicate ack, so i'd like to delay it

Changes in V4:
- Add new host feature bit
- Replace using fixed header lenght with dynamic header lenght in VirtIONet
- Change ip/ip6 header union in NetRscUnit to void* pointer
- Add macro prefix, adjust code indent, etc.

Changes in V3:
- Removed big param list, replace it with 'NetRscUnit'
- Different virtio header size
- Modify callback function to direct call.
- Needn't check the failure of g_malloc()
- Other code format adjustment, macro naming, etc

Changes in 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
Feature information:

Both IPv4 and IPv6 are supported, though performance with userspace virtio
is slow than vhost-net, there is about 1.5x to 2x performance improvement to
userspace virtio, this is done by turning this feature on and disable
'tso/gso/gro' on corresponding tap interface and guest interface, while get
less improment with all these feature on.

Linux guest performance data(Netperf):
() port 0 AF_INET : nodelay
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

  87380  16384     64    6.00     1221.20
  87380  16384     64    6.00     1260.30

  87380  16384    128    6.00     1978.51
  87380  16384    128    6.00     2286.05

  87380  16384    256    6.00     2677.94
  87380  16384    256    6.00     4615.42

  87380  16384    512    6.00     2956.54
  87380  16384    512    6.00     5356.39

  87380  16384   1024    6.00     2798.17
  87380  16384   1024    6.00     4943.30

  87380  16384   2048    6.00     2681.09
  87380  16384   2048    6.00     4835.81

  87380  16384   4096    6.00     3390.14
  87380  16384   4096    6.00     5391.54

  87380  16384   8092    6.00     3008.27
  87380  16384   8092    6.00     5381.68

  87380  16384  10240    6.00     2999.89
  87380  16384  10240    6.00     5393.11

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 running on 2 linux guest, thus i can
the traffic and debugging the code as i want.
2. Netperf on linux guest test the throughput.
3. WHQL test with 2 Windows guests.

Wei Xu (2):
   virtio-net rsc: support coalescing ipv4 tcp traffic
   virtio-net rsc: support coalescing ipv6 tcp traffic

  hw/net/virtio-net.c                         | 623 +++++++++++++++++++++++++++-
  include/hw/virtio/virtio-net.h              |   2 +
  include/hw/virtio/virtio.h                  |  75 ++++
  include/standard-headers/linux/virtio_net.h |   2 +
  4 files changed, 699 insertions(+), 3 deletions(-)

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