Re: [PATCH v4 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue

Toke Høiland-Jørgensen
2019-10-23T09:52:18Z

Toke Høiland-Jørgensen <toke@redhat.com> writes:

> Kan Yan <kyan@google.com> writes:
>
>>> >> + if (ieee80211_is_data_qos(hdr->frame_control)) {
>>> >> + qc = ieee80211_get_qos_ctl(hdr);
>>> >> + tid = qc[0] & 0xf;
>>> >> + ac = ieee80211_ac_from_tid(tid);
>>> >> + } else {
>>> >> + ac = IEEE80211_AC_BE;
>>> >> + }
>>> >
>>> > The tid/ac is incorrect either here or in __ieee80211_tx_status() when
>>> > tested with ath10k. The ac is set to AC_BE with test done using BK
>>> > class traffic, hence the pending airtime get updated for the wrong
>>> > txq.
>>>
>>> Huh, well that won't do, obviously :)
>>>
>>> Any idea why it might be wrong?
>>
>> somehow ieee80211_is_data_qos() returns false. Besides, qos_control
>> field doesn't seems to be set in ieee80211_build_hdr().
>>
>>> Hmm, I guess we could just get the ac using skb_get_queue_mapping().
>>> I'll send an update with this fixed for you to try :)
>> Thanks for the quick update. It is getting much better, but
>> unfortunately the pending airtime accounting sometimes is still not
>> correct and cause txq stuck occasionally.
>
> OK, so that has to mean that there are packets getting dropped somewhere
> without going through ieee80211_report_used_skb(). Assuming you're not
> hitting the underflow warnings, just seeing the counter not get back
> down to zero?
>
> Could you see if you can find out if ath10k does that anywhere? I'll go
> hunting in mac80211.
>
> Looking for calls to kfree_skb() or kfree_skb_list() should hopefully
> turn up something...

Aha! Turns out I was doing the sta lookup completely wrong in
ieee80211_report_used_skb(); so anything frames that were dropped and
went through there would not get its airtime subtracted correctly. Will
send a v6 with a fix :)

-Toke