[ovs-dev] [PATCH v4 3/3] netdev-dpdk: Add TCP Segmentation Offload support

Ilya Maximets i.maximets at ovn.org
Fri Jan 17 16:10:33 UTC 2020


On 17.01.2020 15:23, Stokes, Ian wrote:
> 
> 
> On 1/16/2020 5:00 PM, Flavio Leitner wrote:
>> Abbreviated as TSO, TCP Segmentation Offload is a feature which enables
>> the network stack to delegate the TCP segmentation to the NIC reducing
>> the per packet CPU overhead.
>>
>> A guest using vhostuser interface with TSO enabled can send TCP packets
>> much bigger than the MTU, which saves CPU cycles normally used to break
>> the packets down to MTU size and to calculate checksums.
>>
>> It also saves CPU cycles used to parse multiple packets/headers during
>> the packet processing inside virtual switch.
>>
>> If the destination of the packet is another guest in the same host, then
>> the same big packet can be sent through a vhostuser interface skipping
>> the segmentation completely. However, if the destination is not local,
>> the NIC hardware is instructed to do the TCP segmentation and checksum
>> calculation.
>>
>> It is recommended to check if NIC hardware supports TSO before enabling
>> the feature, which is off by default. For additional information please
>> check the tso.rst document.
> 
> Thanks for the patch Flavio,
> 
> Ciara has vaidated the series and no issues found on our side.
> 
> @Ilya, any concerns on your side? Any reason to blocking this to merge?

I'm looking at patches now.  Will reply soon with results.

One thing is that I'm asking to rename patches before pushing them
to master due to incorrect 'area':

vhost: Disable multi-segmented buffers
-->  netdev-dpdk: Disable multi-segmented buffers for vhost.

netdev-dpdk: Add TCP Segmentation Offload support
-->  userspace: Add TCP Segmentation Offload support.

Best regards, Ilya Maximets.


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