[Make-wifi-fast] tx queue stuck for many minutes

[Joshua Zhao]

and, BTW, what's best way to disable or skip AQM for comparison purposes?

Thanks!
Joshua

On Thu, Apr 11, 2019 at 4:38 PM Joshua Zhao <swzhao at gmail.com> wrote:

> Hi,
> I run into a weird symptom that occasionally the aqm tx queue can get
> stuck for quite long time (maybe around 30min).  What happened is that
> we're sending a low bandwidth UDP traffic from the host to multiple peers
> over a WiFi radio simultaneously. We're running opensource mac80211 +
> ath10k driver. Very occasionally when there are temporary issues causing
> trouble on the host sending to one of the peers, the queue to all peers can
> get stuck and stay stuck for quite long (even though the link trouble had
> been gone or TX had been stopped). Only after quite a while, then the queue
> cleans up.
> The following dump shows an example that the backlog-packets count stays
> at 74 for around 30min after the TX had totally stopped. Here when video
> queue is stuck, other TID's traffic can go through.
> I wonder why it takes so long for the queue to clean up. Shouldn't packets
> be dropped quickly if they cannot be sent?
>
> Many thanks!
>
> cat /sys/kernel/debug/ieee80211/phy0/netdev:wlan3/stations/xx:xx:xx/aqm
>
> target 19999us interval 99999us ecn yes
>
> tid ac backlog-bytes backlog-packets new-flows drops marks overlimit
> collisions tx-bytes tx-packets
>
> 0 2 0 0 3 0 0 0 0 390 3
>
> 1 3 0 0 0 0 0 0 0 0 0
>
> 2 3 0 0 0 0 0 0 0 0 0
>
> 3 2 0 0 0 0 0 0 0 0 0
>
> 4 1 0 0 0 0 0 0 0 0 0
>
> 5 1 112344 74 1627 0 0 0 0 2373618 1632
>
> 6 0 0 0 0 0 0 0 0 0 0
>
> 7 0 0 0 1 0 0 0 0 32 1
>
> 8 2 0 0 0 0 0 0 0 0 0
>
> 9 3 0 0 0 0 0 0 0 0 0
>
> 10 3 0 0 0 0 0 0 0 0 0
>
> 11 2 0 0 0 0 0 0 0 0 0
>
> 12 1 0 0 0 0 0 0 0 0 0
>
> 13 1 0 0 0 0 0 0 0 0 0
>
> 14 0 0 0 0 0 0 0 0 0 0
>
> 15 0 0 0 0 0 0 0 0 0 0
>
>
>
>
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