netdev - Performance regression on lan966x when extracting frames

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Date: Mon, 15 May 2023 11:12:26 +0200
From: Horatiu Vultur <horatiu.vultur@...rochip.com>
To: <edumazet@...gle.com>, <netdev@...r.kernel.org>
Subject: Performance regression on lan966x when extracting frames

Hi,

I have noticed that on the HEAD of net-next[0] there is a performance drop
for lan966x when extracting frames towards the CPU. Lan966x has a Cortex
A7 CPU. All the tests are done using iperf3 command like this:
'iperf3 -c 10.97.10.1 -R'

So on net-next, I can see the following:
[  5]   0.00-10.01  sec   473 MBytes   396 Mbits/sec  456 sender
And it gets around ~97000 interrupts.

While going back to the commit[1], I can see the following:
[  5]   0.00-10.02  sec   632 MBytes   529 Mbits/sec   11 sender
And it gets around ~1000 interrupts.

I have done a little bit of searching and I have noticed that this
commit [2] introduce the regression.
I have tried to revert this commit on net-next and tried again, then I
can see much better results but not exactly the same:
[  5]   0.00-10.01  sec   616 MBytes   516 Mbits/sec    0 sender
And it gets around ~700 interrupts.

So my question is, was I supposed to change something in lan966x driver?
or is there a bug in lan966x driver that pop up because of this change?

Any advice will be great. Thanks!

[0] befcc1fce564 ("sfc: fix use-after-free in efx_tc_flower_record_encap_match()")
[1] d4671cb96fa3 ("Merge branch 'lan966x-tx-rx-improve'")
[2] 8b43fd3d1d7d ("net: optimize ____napi_schedule() to avoid extra NET_RX_SOFTIRQ")

-- 
/Horatiu