From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.toke.dk (mail.toke.dk [IPv6:2001:470:dc45:1000::1]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id A608F3B29E for ; Tue, 24 Apr 2018 10:34:02 -0400 (EDT) From: Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=toke.dk; s=20161023; t=1524580441; bh=pg8fRMfsT5IjQ62PgMY2K1bpBRLyO3Y2pO5bZJU2O3E=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=iFhk0ep74CG6WcdUTK760XYR3r+Y9Bum+BHWw0lPwmUKcelxTfyX2jSmR9R5iVsrv kZDomog1Q2WXblOoiNFEiJy/Frb0snV3lM04Rn+fgUAc5xfFgQRM3fZStmbSxw69BJ Q74W94/ZrXLN9I/7yKqN9f2pFoy2Khscg6PlYl9jJsMLLQ203Ad4GqJGLmjUoePgYh LxJ08k/YaJ31GT3G5Mh2HAiMuA+INpv03BMdCzb9H/N+wYSluH/2c5MBTojdT8+2vq yLTS6FFuHH+/ezpGKPzPag3SO1sNKRyyrOoXt3IfVuTrh5DOPHwDSxHkGck7T7zS6E YT7lRaGEYOyXg== To: Pete Heist Cc: make-wifi-fast@lists.bufferbloat.net In-Reply-To: <1BA3CECA-8C05-4E94-9E2A-1AEA3C2F20B3@eventide.io> References: <66BDCA6E-D7C4-4E76-8591-8FDC35B09EA3@eventide.io> <871sf495vs.fsf@toke.dk> <87po2o7lwb.fsf@toke.dk> <1BA3CECA-8C05-4E94-9E2A-1AEA3C2F20B3@eventide.io> Date: Tue, 24 Apr 2018 16:34:00 +0200 X-Clacks-Overhead: GNU Terry Pratchett Message-ID: <87k1sw7jxj.fsf@toke.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Make-wifi-fast] mesh deployment with ath9k driver changes X-BeenThere: make-wifi-fast@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 24 Apr 2018 14:34:02 -0000 Pete Heist writes: >> On Apr 24, 2018, at 3:51 PM, Toke H=C3=B8iland-J=C3=B8rgensen wrote: >>=20 >> Assuming you have debugfs enabled you should be able to get aggregate >> statistics from /sys/kernel/debug/ieee80211/phy0/ath9k/xmit - at least >> that contains retries, but not backoff data, unfortunately. > > If it=E2=80=99s the ratio of "AMPDUs Completed=E2=80=9D to "AMPDUs Retrie= d=E2=80=9D or =E2=80=9CAMPDUs > XRetried=E2=80=9D we=E2=80=99re looking at, there=E2=80=99s a stark diffe= rence between Cabin > 12 and Cabin 28. That said, they have quite different traffic > patterns, so I=E2=80=99ll have to evaluate this in a situation where traf= fic > patterns are more similar... Yeah. I'm not actually sure how exactly those numbers reflect what happens on the medium (nor what the difference between retried and xretried is), but it's an indication at least. >>> I wish I could cable everything, but it isn=E2=80=99t physically practi= cal. >>> The next possibility is dual channel APs, or separate backhaul links, >>> all costing something... >>=20 >> Yeah, a separate backhaul on a different channel would cut you >> contention in half, basically. Right now, each transmission has to >> occupy the channel twice... > > Could that cause mean RTT to go up 10x? :) In combination with having > two repeaters on one gateway=E2=80=A6 Not sure. You do get HOL blocking while a packet is retried, basically. And ath9k will keep trying way after it should have given up (up to 30 retries per packet). If you combine this with a lot of backoff for each transmission (which is also quite likely in a very congested setting), and I suppose it might be possible... -Toke