Return-path: Received: from nbd.name ([46.4.11.11]:48114 "EHLO nbd.name" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751711Ab3CALbM (ORCPT ); Fri, 1 Mar 2013 06:31:12 -0500 Message-ID: <51309177.2040106@openwrt.org> (sfid-20130301_123117_326823_B82B96DC) Date: Fri, 01 Mar 2013 12:31:03 +0100 From: Felix Fietkau MIME-Version: 1.0 To: Mohammed Shafi CC: Adrian Chadd , Bob Copeland , "Luis R. Rodriguez" , Paul Stewart , Sujith Manoharan , linux-wireless Subject: Re: [RFC] ath9k: remove ath9k_rate_control References: <1360329197-72631-1-git-send-email-nbd@openwrt.org> <20757.1753.863278.858198@gargle.gargle.HOWL> <511508A6.8020104@openwrt.org> <51152D9E.1040106@openwrt.org> <20130227192030.GW12537@pogo> <512ECE01.8010102@openwrt.org> <20130228114724.GB16369@localhost> <512F5709.60907@openwrt.org> <512FAB01.2050104@openwrt.org> <51307F80.4010202@openwrt.org> <513082F8.8080002@openwrt.org> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 2013-03-01 12:18 PM, Mohammed Shafi wrote: > Hi Felix, > > On Fri, Mar 1, 2013 at 3:59 PM, Felix Fietkau wrote: >> On 2013-03-01 11:22 AM, Adrian Chadd wrote: >>> On 1 March 2013 02:14, Felix Fietkau 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. - Felix