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From: Johannes Berg <johannes@sipsolutions.net>
To: Toke =?ISO-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@redhat.com>
Cc: linux-wireless@vger.kernel.org, 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>, Kan Yan
 <kyan@google.com>,  Rajkumar Manoharan <rmanohar@codeaurora.org>, Kevin
 Hayes <kevinhayes@google.com>
Date: Fri, 08 Nov 2019 11:03:15 +0100
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 <157182474063.150713.16132669599100802716.stgit@toke.dk>
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Subject: Re: [Make-wifi-fast] [PATCH v6 1/4] mac80211: Shrink the size of
 ack_frame_id to make room for tx_time_est
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On Wed, 2019-10-23 at 11:59 +0200, Toke Høiland-Jørgensen wrote:
> From: Toke Høiland-Jørgensen <toke@redhat.com>
> 
> To implement airtime queue limiting, we need to keep a running account of
> the estimated airtime of all skbs queued into the device. Do to this
> correctly, we need to store the airtime estimate into the skb so we can
> decrease the outstanding balance when the skb is freed. This means that the
> time estimate must be stored somewhere that will survive for the lifetime
> of the skb.
> 
> To get this, decrease the size of the ack_frame_id field to 6 bits, and
> lower the size of the ID space accordingly. This leaves 10 bits for use for
> tx_time_est, which is enough to store a maximum of 4096 us, if we shift the
> values so they become units of 4us.
> 

I've applied this as preparation.

johannes