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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Kan Yan <kyan@google.com>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        linux-wireless@vger.kernel.org,
        Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
        ath10k@lists.infradead.org, John Crispin <john@phrozen.org>,
        Lorenzo Bianconi <lorenzo@kernel.org>,
        Felix Fietkau <nbd@nbd.name>,
        Rajkumar Manoharan <rmanohar@codeaurora.org>,
        Kevin Hayes <kevinhayes@google.com>
Subject: Re: [PATCH v4 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue
In-Reply-To: <87tv7znact.fsf@toke.dk>
References: <157148503415.2989444.7391437309981941226.stgit@toke.dk> <157148503865.2989444.7118792679603045723.stgit@toke.dk> <CA+iem5sy16=xMZjJi1nKHrxP_xWHk-86G=ZLwtMMb04EOt5tQA@mail.gmail.com> <871rv5ovwr.fsf@toke.dk> <CA+iem5tZ95Jd9htLEdAJMubuFeWeUibK9MhTnTHLWNucX6_cRg@mail.gmail.com> <87tv7znact.fsf@toke.dk>
Date:   Wed, 23 Oct 2019 11:52:02 +0200
Message-ID: <87lftbn60t.fsf@toke.dk>
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Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com> writes:

> Kan Yan <kyan@google.com> writes:
>
>>> >> +               if (ieee80211_is_data_qos(hdr->frame_control)) {
>>> >> +                       qc =3D ieee80211_get_qos_ctl(hdr);
>>> >> +                       tid =3D qc[0] & 0xf;
>>> >> +                       ac =3D ieee80211_ac_from_tid(tid);
>>> >> +               } else {
>>> >> +                       ac =3D IEEE80211_AC_BE;
>>> >> +               }
>>> >
>>> > The tid/ac is incorrect either here or in __ieee80211_tx_status() whe=
n
>>> > 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