Received-SPF: pass (google.com: best guess record for domain of linux-wireless-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Message-ID: <1580323191.26012.48.camel@gmail.com>
Subject: Strange performance issue when using two devices at once
From:   Marlon Smith <marlon.smith10@gmail.com>
To:     linux-wireless@vger.kernel.org
Date:   Wed, 29 Jan 2020 13:39:51 -0500
Content-Type: text/plain; charset="UTF-8"
Mime-Version: 1.0
Content-Transfer-Encoding: 8bit
Sender: linux-wireless-owner@vger.kernel.org
Precedence: bulk

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