Strange performance issue when using two devices at once

[Marlon Smith <marlon.smith10@gmail.com>]

Hi everyone,

I have two RT5370 devices connected to the same access point. Both
devices are very slow, but the instant I disconnect one device, the
other speeds up by a factor of 10.

The really strange part is that one device will perform slowly even if
the other device is basically idle! I've confirmed this with a packet
sniffer.

I've been trying to do some debugging, and I've found that when both
devices are connected to the access point, they report a large number
of duplicate frames. I added some debug output
in ieee80211_rx_h_check_dup() to confirm that this only happens while
both devices are connected. The packet sniffer also shows a large
number of retries while this is occurring.

Using backports 5.3-rc4 for this, but also tested on 4.14-rc2.

I did post about this previously on this mailing list (RT5370
performance issues), but I thought I'd post again with this new
information and more descriptive title. I'm a little bit stuck on this
for a while now, so any ideas are much appreciated.

Thanks!

Marlon