On 2013-03-01 1:32 PM, Mohammed Shafi wrote: > On Fri, Mar 1, 2013 at 5:01 PM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >> On 2013-03-01 12:18 PM, Mohammed Shafi wrote: >>> Hi Felix, >>> >>> On Fri, Mar 1, 2013 at 3:59 PM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >>>> On 2013-03-01 11:22 AM, Adrian Chadd wrote: >>>>> On 1 March 2013 02:14, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >>>>> >>>>>>> Having access to schedule which peer and how much to send to each peer >>>>>>> would be nice. Stuff like "peer X only can have up to x ms in this WME >>>>>>> class this round", so you don't have a busy, close peer monopolising >>>>>>> the air. It also means you can start doing smart things with far away >>>>>>> peers who retransmit a lot - they're likely tying up a lot of airtime. >>>>>>> >>>>>>> None of this is new. It's just, you know, new to open source. :-) >>>>> >>>>>> In my opinion this doesn't really belong into a rate control module. >>>>>> There should be a tx scheduling API to take care of this. Before I >>>>>> implement something like this, I plan on exposing all per-station driver >>>>>> queues to mac80211. This is necessary for a few other things anyway, >>>>>> e.g. unifying software aggregation logic and fixing its buffer management. >>>>> >>>>> Sure, but then some more clever tricks end up being difficult to >>>>> implement. For example, knowing if a client is tying up too much >>>>> airtime at the given rate and whether to back them off for a bit. Or >>>>> to use smaller aggregation limits for certain clients because your'e >>>>> trying to be "fairer" when trying to keep latency low. That kind of >>>>> thing. >>>>> >>>>> I think "rate control" should likely be expanded to "tx scheduling" as >>>>> a whole, rather than sitting as a separate thing that just selects the >>>>> rate for a node who has already been chosen to transmit. >>>> Even with client airtime use, I still don't see how tx scheduling and >>>> rate control belong together. In my opinion, the rate selection should >>>> not be based on client airtime usage or the current load, as it can >>>> optimize for throughput/airtime ratio without it. >>>> >>> >>> Algorithm folks and Engineers had spent considerable time on ath9k rate control. >>> Wouldn't be a great idea to remove it completely, We can have it optional. >>> With lot of throughput tests ran over internally and with the test >>> team verification, >>> it wouldn't be fair to throw it away. >> Regardless of how much time was spent tuning it, it still has a really >> bad design, bad implementation and a number of practical issues. >> It seems to be tuned entirely for artificial benchmarks in clean air. It >> also starts with a very high rate without having proven that it works. >> I don't think anybody is going to fix all of these issues, and even if >> somebody does, it would invalidate pretty much all of the tuning/testing >> that went into this code. >> > > We can certainly question the design and implementation, but it was proven > to work well and had been tested by more hands(even with propitiatory stuff). > Even if some one thinks it as bad, we should still allow it as an option. > For instance if the environment is pretty good/pretty bad, we should give > the users an option to choose between the two, that's why we should retain > it. I agree that we should keep it for a while, but we should probably change the default soon. As for giving *users* the option of choosing rate control based on the environment, I think it's a bad idea! Regular users can't really be expected to know enough about the details of rate control to make a meaningful decision, nor should they be. Simply being lazy and telling every user to just test which one works better for them is also a bad idea. The default implementation needs to be good for all kinds of environments. minstrel_ht is already tuned to work quite well in tough environments with heavy interference, so closing the performance gap in clean environments should be quite easy. The main thing I need to get that done is good quality test feedback - something that I didn't get a lot of, neither from users, nor from QCA. > Further its been tested internally, by customers and more folks. Right, and a few of those customers complained about bad performance with ath9k, and also reported that switching to minstrel_ht fixed their issues :) Good to know that it's been tested, but where are the results? Who is going to take care of the long standing *known* issues? One of these issues (too high bitrate before rate feedback is available) led to somebody from Google hacking up a crappy workaround in wpa_supplicant that disables high bitrates during connect. Saying that it has been tested does not necessarily imply that it's any good or that it works properly in all normal scenarios ;) > Its been also worked by some serious developers and Engineers. Well, I do consider myself a serious developer and engineer as well :) - Felix -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
