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Re: [Qemu-devel] [ Patch 0/2] Support Receive-Segment-Offload(RSC) for W

From: Jason Wang
Subject: Re: [Qemu-devel] [ Patch 0/2] Support Receive-Segment-Offload(RSC) for WHQL test of Window guest
Date: Fri, 18 Mar 2016 10:22:12 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.1

On 03/18/2016 12:57 AM, Wei Xu wrote:
> On 2016年03月17日 23:44, Michael S. Tsirkin wrote:
>> On Thu, Mar 17, 2016 at 11:21:28PM +0800, Wei Xu wrote:
>>> On 2016年03月17日 14:47, Jason Wang wrote:
>>>> On 03/15/2016 05:17 PM,address@hidden  wrote:
>>>>> From: Wei Xu<address@hidden>
>>>>> Fixed issues based on rfc patch v2:
>>>>> 1. Removed big param list, replace it with 'NetRscUnit'
>>>>> 2. Different virtio header size
>>>>> 3. Modify callback function to direct call.
>>>>> 4. Needn't check the failure of g_malloc()
>>>>> 5. Other code format adjustment, macro naming, etc
>>>>> 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 1x to 3x 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.
>>>>> 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 control
>>>>> the traffic and debugging the code as i want.
>>>>> 2. Netperf on linux guest test the throughput.
>>>>> 3. WHQL test with 2 Windows guests.
>>>>> 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, looks like the test traffic is
>>>>> not sent from
>>>>> on the support machine, test device can access both host and
>>>>> another linux
>>>>> guest, tried a lot of ways to work it out but failed, maybe debug
>>>>> from windows
>>>>> guest driver side can help figuring it out.
>>>> I think you need figure out where was the packet dropped first. If the
>>>> packet was not dropped by windows guest, you may want to try
>>>> dropmonitor.
>>> Yes, there is something wrong with my previous description, i add
>>> some debug
>>> code and did new test, the packets are received by
>>> virtio_net_receive() and
>>> are finished putting to the vring with no error and sent to win guest
>>> already, but wireshark on win guest doesn't get it, because the test
>>> case
>>> did some hacking on the filter, it installed another lightweight
>>> filter, i'm
>>> not sure how these packets go in the guest, maybe they are received but
>>> dropped by driver or stack, etc.
>> Add some debug output in the driver, rebuild it and see packets
>> as they are received and passed up the stack.
> Yes, but this is to win guest, i tried to build a windows debug binary
> but failed, is there any possible missing path in virtio between
> pushed it to vring and notified the guest successfully? i'm sure at
> this by debugging it with gdb.

Is the packet always dropped or does it help if you turn off some
configuration (e.g checksum offloads) works?

>>> I tried 'dropmonitor', it's very interesting but it helps very
>>> limitedly for
>>> windows guest, i can only use it with qemu on the host.
>>>>> 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.
>>>>> Todo:
>>>>> More sanity check and tcp 'ecn' and 'window' scale test.
>>>>> Wei Xu (2):
>>>>>    virtio-net rsc: support coalescing ipv4 tcp traffic
>>>>>    virtio-net rsc: support coalescing ipv6 tcp traffic
>>>>>   hw/net/virtio-net.c            | 602
>>>>> ++++++++++++++++++++++++++++++++++++++++-
>>>>>   include/hw/virtio/virtio-net.h |   1 +
>>>>>   include/hw/virtio/virtio.h     |  75 +++++
>>>>>   3 files changed, 677 insertions(+), 1 deletion(-)

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