Hi, Sorry for the long time to review here ... On Thu, 2019-09-19 at 14:22 +0200, Toke Høiland-Jørgensen wrote: > From: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > > 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. > > Fortunately, we had a couple of bytes left in the 'status' field in the > ieee80211_tx_info; and since we only plan to calculate the airtime estimate > after the skb is dequeued from the FQ structure, on the control side we can > share the space with the codel enqueue time. And by rearranging the order > of elements it is possible to have the position of the new tx_time_est line > up between the control and status structs, so the value will survive from > when mac80211 hands the packet to the driver, and until the driver either > frees it, or hands it back through TX status. Seems reasonable to me, if we end up needing it and don't have an out- of-band path (that you seem to have been discussing in this long thread too) johannes
