Kan Yan <kyan@xxxxxxxxxx> writes: >> No, ath10k would continue to do what it was always doing. Drivers that >> can report after-the-fact airtime usage per-frame (like ath9k) will >> continue to do that. In both of those cases, the airtime estimate is >> only used to throttle the queue, not to schedule for fairness. > You are right, I didn't realize ath9k reports per frame airtime usage. > >> Yeah, I was wondering about that. Makes sense. Why 24ms, exactly? > The per interface 24 ms queue limit is an empirical number that works > well for both achieve low latency when there is a lot of stations and > get high throughput when there is only 1-2 stations. We could make it > configurable. Right. "Found by trial and error" is a fine answer as far as I'm concerned :) But yeah, this should probably be configurable, like BQL is. >> BTW, I think Felix' concern about powersave was in relation to AQL: If >> we don't handle power save in that, we can end up in a situation where >>the budget for packets allowed to be queued in the firmware is taken up >> entirely by stations that are currently in powersave mode; which would >> throttle the device completely. So we should take that into account for >> AQL; for the fairness scheduler, stations in powersave are already >> unscheduled, so that should be fine. > I think the accounting for the airtime of frames in the power saving > queue could affect both the fairness scheduler and AQL. > For chipset with firmware offload, PS handling is mostly done by > firmware, so host driver's knowledge of PS state could be slightly > out-of-dated. The power save behavior also make it harder to the > airtime_weight correct for the fairness scheduler. Hmm, maybe. I'm not sure how significant this effect would be, but I guess we'll need to find out :) > Powersave mode's impact to AQL is much smaller. The lower per station > queue limit is not impacted by other stations PS behavior, since the > estimated future airtime is not weighted for other stations and a > station won't get blocked due to others stations in PS mode. > Station in PS mode do affects AQL's higher per interface limit, but in > an inconsequential way. The per interface AQL queue limit is quite > large (24 ms), hence airtime from packets in PS queue is unlikely to > have a significant impact on it. Still, it will be better if the > packet in power saving queue can be taken into account. I guess the risk is lower when with a 24ms per-iface limit; but with enough stations I guess it could still happen, no? So we should probably handle this case... >> > make it easier to schedule multiple stations, I think it has some merit >> > that makes it worth trying out. We should probably get the AQL stuff >> > done first, though, and try the virtual time scheduler on top of that. >> Agree that we should get the AQL stuff done first since I believe it >> will help to fix the issue mentioned above. > That sounds like a good plan. The virtual time scheduler is more > involved and will take more work to get it right. It make sense to get > AQL done first. Cool. Are you going to submit a ported version of your implementation? Then we can work from the two submissions and see if we can't converge on something... -Toke
