Re: [PATCH net-next 1/2] selftests/net: GRO coalesce test

Hello,

On Thu, 2021-08-05 at 07:36 +0000, Coco Li wrote:

Implement a GRO testsuite that expects Linux kernel GRO behavior.
All tests pass with the kernel software GRO stack. Run against a device
with hardware GRO to verify that it matches the software stack.

gro.c generates packets and sends them out through a packet socket. The
receiver in gro.c (run separately) receives the packets on a packet
socket, filters them by destination ports using BPF and checks the
packet geometry to see whether GRO was applied.

gro.sh provides a wrapper to run the gro.c in NIC loopback mode.
It is not included in continuous testing because it modifies network
configuration around a physical NIC: gro.sh sets the NIC in loopback
mode, creates macvlan devices on the physical device in separate
namespaces, and sends traffic generated by gro.c between the two
namespaces to observe coalescing behavior.

I like this idea a lot!

Have you considered additionally run the same test of top of a veth
pair, and have such tests always enabled, so we could have some
coverage regardless of specific H/W available?

To do the above you should disable TSO on the veth sender peer and
enable GRO on the other end.

[...]

+  setup_ns
+  # Each test is run 3 times to deflake, because given the receive timing,
+  # not all packets that should coalesce will be considered in the same flow
+  # on every try.

I thought that tuning 'gro_flush_timeout' appropriatelly, you should be
able to control exactly which packets will be aggregated ???

Thanks!

Paolo