On Wed, 2019-12-11 at 15:47 +0100, Toke Høiland-Jørgensen wrote: > > Say you have some queues - some (Q1-Qn) got a LOT of traffic, and > > another (Q0) just has some interactive traffic. > > > > You could then end up in a situation where you have 24ms queued up on > > Q1-Qn (with n high enough to not have hit the per-queue AQL limit), > > right? > > > > Say also the last frame on Q0 was dequeued by the hardware, but the > > tx_dequeue() got NULL because of the AQL limit having been eaten up by > > all the packets on Q1-Qn. > > > > Now you'll no longer get a new dequeue attempt on Q0 (it was already > > empty last time, so no hardware reclaim to trigger new dequeues), and a > > new dequeue on the *other* queues will not do anything for this queue. > > Oh, right, I see; yeah, that could probably happen. I guess we could > either kick all available queues whenever the global limit goes from > "above" to "below"; or we could remove the "return NULL" logic from > tx_dequeue() and rely on next_txq() to throttle. I think the latter is > probably simpler, but I'm a little worried that the throttling will > become too lax (because the driver can keep dequeueing in the same > scheduling round)... I honestly have no idea what's better ... :) You're the expert, I'm just poking holes into it ;-) johannes
