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Subject: Re: Strange performance issue when using two devices at once
To:     Marlon Smith <marlon.smith10@gmail.com>,
        linux-wireless@vger.kernel.org
References: <1580323191.26012.48.camel@gmail.com>
From:   Ben Greear <greearb@candelatech.com>
Organization: Candela Technologies
Message-ID: <2e80a485-892d-3b29-19c7-38a9caa14f4b@candelatech.com>
Date:   Wed, 29 Jan 2020 10:42:07 -0800
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On 1/29/20 10:39 AM, Marlon Smith wrote:
> 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.

Out of curiosity, are both of the RT5370 used on the same client device?

Did you check that they have unique MAC addresses?

Thanks,
Ben

> 
> 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
> 


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