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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Johannes Berg <johannes@sipsolutions.net>,
        Kan Yan <kyan@google.com>
Cc:     linux-wireless@vger.kernel.org,
        make-wifi-fast@lists.bufferbloat.net, nbd@nbd.name,
        yiboz@codeaurora.org, john@phrozen.org, lorenzo@kernel.org,
        rmanohar@codeaurora.org, kevinhayes@google.com
Subject: Re: [PATCH v11 2/4] mac80211: Import airtime calculation code from mt76
In-Reply-To: <3e7bea0cc643714ec90978a7999022544a39b118.camel@sipsolutions.net>
References: <20191119060610.76681-1-kyan@google.com> <20191119060610.76681-3-kyan@google.com> <3e7bea0cc643714ec90978a7999022544a39b118.camel@sipsolutions.net>
Date:   Fri, 22 Nov 2019 13:56:25 +0100
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Johannes Berg <johannes@sipsolutions.net> writes:

> On Mon, 2019-11-18 at 22:06 -0800, Kan Yan wrote:
>> From: Toke H=C3=B8iland-J=C3=B8rgensen <toke@redhat.com>
>>=20
>> Felix recently added code to calculate airtime of packets to the mt76
>> driver. Import this into mac80211 so we can use it for airtime queue lim=
it
>> calculations.
>>=20
>> The airtime.c file is copied verbatim from the mt76 driver, and adjusted=
 to
>> be usable in mac80211. This involves:
>>=20
>> - Switching to mac80211 data structures.
>> - Adding support for 160 MHz channels and HE mode.
>> - Moving the symbol and duration calculations around a bit to avoid
>>   rounding with the higher rates and longer symbol times used for HE rat=
es.
>
> :)
>
> I'll apply this, I guess,

Great!

> but I do wonder to what extent it overlaps with
> cfg80211_calculate_bitrate()?

Well, one calculates bitrates while the other calculates airtime? ;)

But yeah, I get what you mean. I think Felix went through quite some
pains to structure this code to avoid divisions in the fast path. I
guess that is the main blocker for cfg80211_calculate_bitrate() to be
used instead (assuming we do want to consolidate them eventually). Not
sure if that can be fixed easily though?

-Toke