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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Miguel Catalan Cid <miguel.catalan@i2cat.net>
Cc:     make-wifi-fast@lists.bufferbloat.net,
        linux-wireless@vger.kernel.org
Subject: Re: [Make-wifi-fast] Support for airtime scheduling using ath10k
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Date:   Mon, 29 Jun 2020 12:25:56 +0200
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Miguel Catalan Cid <miguel.catalan@i2cat.net> writes:

> El mar., 23 jun. 2020 a las 11:35, Toke H=C3=B8iland-J=C3=B8rgensen
> (<toke@redhat.com>) escribi=C3=B3:
>>
>> Miguel Catalan Cid <miguel.catalan@i2cat.net> writes:
>>
>> > Hi,
>> >
>> > we are trying to apply different airtime weights to different stations=
 in
>> > order to have some prioritization among connected stations. While this=
 is
>> > working pretty well with ath9k, with ath10k we always obtain a fair
>> > distribution of the airtime (i.e. 50%-50% in the case of two stations),
>> > regardless of the airtime weight specified.
>> >
>> > E.g. STA1:
>> > RX: 0 us
>> > TX: 2295610622 us
>> >
>> > *Weight: 200*Deficit: VO: 256 us VI: 256 us BE: 34 us BK: 256 us
>> >
>> > E.g. STA2:
>> > RX: 0 us
>> > TX: 162597077 us
>>
>> 2295610622/162597077 ~=3D 14
>>
>> which is not *too* far from the 20/1 ratio you've configured? Does the
>> ratio change at all when you change the weights (i.e., if they are
>> equal, do you get closer to a 50/50 split?).
>>
>> Do the two stations have roughly the same signal strength / rate?
>
> In this case I started the STA1 a bit earlier, so it had a higher
> airtime aggregate. Indeed, to compare the airtime share, I was
> continuously monitoring the "airtime rate" (i.e. the difference
> between Airtime(now) and Airtime (now-4s)) and the results of both
> STAs were the same (i.e. 50/50 split) independently of the weight
> being used. But when using ath9k the same test runs perfectly
> according to the weights.
>
>>
>> > *Weight: 10*Deficit: VO: 256 us VI: 256 us BE: 9 us BK: 256 us
>> >
>> > We are using Compex WLE650V5-18A cards.
>> >
>> > So, does ath10k support airtime scheduling? In such a case, do we need
>> > specific Wi-Fi cards?
>>
>> It should. My guess would be that maybe you're not getting enough
>> backpressure for the scheduler to actually enforce things correctly. You
>> could try to look at the TXQ output and see if you actually have any
>> drops ('iw dev wlan0 station dump -v' and look at the drops/marks
>> columns).
>
> ok, i will check!

Another thing to check is the value of 'new_flows' in the TXQ output; if
that is high, it indicates that the queues run empty a lot, which can
prevent the airtime fairness scheduler from working properly.

>> What kernel version are you running? If it's not new enough to have AQL,
>> that might help moving the backlog to where the scheduler can do more
>> with it.
>
> Kernel 5.5.5.

Hmm, that should have AQL, actually.

-Toke