On 2016-09-08 21:59, Toke Høiland-Jørgensen wrote: > CoDel can be too aggressive if a station sends at a very low rate. This > gets worse the more stations are present, as each station gets more > bursty the longer the round-robin scheduling between stations takes. > > This is an attempt to dynamically adjust CoDel parameters per station. > It takes a rather simple approach and uses a simple binary designation > of a station as 'slow' if it has expected throughput less than eight > Mbps (i.e. the lowest couple of rates). In this case, CoDel is set to be > more lenient by adjusting its target to 50 ms and interval to 300 ms. > There's a built-in hysteresis so a station cannot flip between slow and > fast more than once every two seconds. > > In this version the check is performed every time a packet is enqueued > to the intermediate queues; and the overhead of doing this is alleviated > a bit by caching the result and by the above-mentioned hysteresis. It > can probably be smarter about both when and how to do the scaling, but > this seems to alleviate some of the starvation I've seen with very slow > stations. Since this is not dealing properly with firmware rate control anyway, I'd suggest calling the update from rate_control_set_rates in order to avoid putting more stuff into the tx hot path. You could add a separate code path to allow firmware rate control devices to provide a hint at a convenient point in time. - Felix
