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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Justin Capella <justincapella@gmail.com>
Cc:     Johannes Berg <johannes@sipsolutions.net>,
        linux-wireless <linux-wireless@vger.kernel.org>,
        make-wifi-fast@lists.bufferbloat.net, nbd@nbd.name,
        Yibo Zhao <yiboz@codeaurora.org>,
        John Crispin <john@phrozen.org>, lorenzo@kernel.org,
        rmanohar@codeaurora.org, kevinhayes@google.com,
        Kan Yan <kyan@google.com>
Subject: Re: [PATCH v11 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue
In-Reply-To: <CAMrEMU8FkUkoTB95K8cbBgcrUBPmE0cy6yUcROLTw1_BuSCKuQ@mail.gmail.com>
References: <20191119060610.76681-1-kyan@google.com> <20191119060610.76681-5-kyan@google.com> <CAMrEMU8FkUkoTB95K8cbBgcrUBPmE0cy6yUcROLTw1_BuSCKuQ@mail.gmail.com>
Date:   Thu, 27 Feb 2020 11:17:05 +0100
Message-ID: <8736awxrku.fsf@toke.dk>
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Justin Capella <justincapella@gmail.com> writes:

>> ieee80211_report_used_skb(). As an optimisation, we also subtract the
>> airtime on regular TX completion, zeroing out the value stored in the
>> packet afterwards, to avoid having to do an expensive lookup of the station
>> from the packet data on every packet.
>>
>> This patch does *not* include any mechanism to wake a throttled TXQ again,
>> on the assumption that this will happen anyway as a side effect of whatever
>> freed the skb (most commonly a TX completion).
>
> I recall a recent patch for ath10k sdio that disabled tx
> acknowledgement for performance gains and am wondering if that will be
> problematic? Presumably not since it would be caught at the dequeue,
> but thought I'd ask-- wondering what the effect of failed tx's or
> block acknowledgement is on this stuff I'll need to study the code
> some more
>
> https://lore.kernel.org/linux-wireless/0101016eb1903db0-ef7063b4-0f42-4a01-8886-327541e6c1a4-000000@us-west-2.amazonses.com/T/#t

It looks like that patch will just end up disabling AQL (because packets
will be immediately completed as far as mac80211 is concerned) and
replace it with whatever that credit-based scheme does? No idea how that
will impact latency; you should go ask the developers of that series! As
usual, the patch description only mentions throughput numbers :/

-Toke