netdev - net: tso: add UDP segmentation support: adds regression for ax200 upload

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Message-ID: <5664fa0f-aef2-c336-651a-093c9eed23ab@candelatech.com>
Date:   Wed, 16 Dec 2020 15:09:22 -0800
From:   Ben Greear <greearb@...delatech.com>
To:     netdev <netdev@...r.kernel.org>, edumazet@...gle.com
Subject: net: tso: add UDP segmentation support: adds regression for ax200
 upload

Hello Eric,

The patch below evidently causes TCP throughput to be about 50Mbps instead of 700Mbps
when using ax200 to upload tcp traffic.

When I disable TSO, performance goes back up to around 700Mbps.

I recall ~5 years ago we had similar TCP related performance issues with ath10k.
I vaguely recall that there might be some driver-level socket pacing tuning value, but I cannot
find the right thing to search for.  Is this really a thing?  If so, maybe it will
be a way to resolve this issue?

See this more thorough bug report:

https://bugzilla.kernel.org/show_bug.cgi?id=209913

Patch description:
net: tso: add UDP segmentation support
Note that like TCP, we do not support additional encapsulations,
and that checksums must be offloaded to the NIC.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>

Thanks,
Ben

-- 
Ben Greear <greearb@...delatech.com>
Candela Technologies Inc  http://www.candelatech.com