From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lj1-x241.google.com (mail-lj1-x241.google.com [IPv6:2a00:1450:4864:20::241]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id E8C6E3B29D for ; Tue, 26 Nov 2019 00:04:36 -0500 (EST) Received: by mail-lj1-x241.google.com with SMTP id d5so18603084ljl.4 for ; Mon, 25 Nov 2019 21:04:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc:content-transfer-encoding; bh=JQSdHWPAU2nitRvT0Di7Ib4QABBb5+QiA8tiP3X9DWM=; b=lRned6cZi6/wDX1xJ1HLugPH2HIWLAYfrFFbV5Y5oAcFWELce6f+opZWj8td6z0XNB k8QaFu+1RuA6mRb6k5xImAYyuEqIs/5RktUh92Mf1W/F9z/AaiEK+lGAUctcjdbJj4RR 7cIdRNW6MzmSYifH29aeislagfZslmXmofI5n55rTGY6AYHNYnAzXu/OQfLxhoOOzFP2 MMmVDBGqiuDpDvGwnDsqdMC3TlTl4xlDDzzyxZmRx9shgiXdB2xjfmG+wnXw9dqWE1ak jU3JPtw85qRh/Wex4UWXpT6hECE89NXzNikKzqO9jc1HxjBzorcm53qyHJzNYjs/wG/W 99xg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc:content-transfer-encoding; bh=JQSdHWPAU2nitRvT0Di7Ib4QABBb5+QiA8tiP3X9DWM=; b=aYtJXNs1RUwLxT0l980SAvh5kqvhBA7kyCUGEJI9TDPxH4MLsNoB5Mzoz00/HufQ+w 3Uf4sU/K5npRjMGKzxr0V3B1Uk0UoyyQxfSqgOoajNqDbv6640auAvpaleG0gozJLENg iqun4Ru8Xuk1CvNubj8f5kZuBUbok75tpKOlayXH5cNuDrDj/iP9QcZ65jy2/Zf7wx2C drO4T0sqhsS6wa2gm097o7r0kWMUVHh2am4wu4bEL7QI8Bi8hURHZJdm336ZvPLkyFCB GqxxaSLf7D6xBh2aChlkU9P1Ikc9qTPq+93CPv9ZU0dzoG0MbBWEHsNj8J/bn19RJIvJ AP8Q== X-Gm-Message-State: APjAAAXol11fkdQB84pygUYIpodYjhYIMCJB+POaeduj3BEbAV3cLre0 0ONMPzwNlXfH/R0s3VUutTKw7inzECHTT8x1Ox7S/KlXSnM= X-Google-Smtp-Source: APXvYqyw6ShEcPeBSRIAOlL/m3Z6ruiZ+OtmTjgBZIE0N6S7H2FMAooQF4M3qp5TnHittIM67oemZRzavLd2PRI/zHI= X-Received: by 2002:a2e:574d:: with SMTP id r13mr24686240ljd.10.1574744675047; Mon, 25 Nov 2019 21:04:35 -0800 (PST) MIME-Version: 1.0 References: <20191115014846.126007-1-kyan@google.com> <8736eiam8f.fsf@toke.dk> <87a78p8rz7.fsf@toke.dk> <87muco5gv5.fsf@toke.dk> In-Reply-To: <87muco5gv5.fsf@toke.dk> From: Kan Yan Date: Mon, 25 Nov 2019 21:04:23 -0800 Message-ID: Subject: Re: [Make-wifi-fast] [PATCH v8 0/2] Implement Airtime-based Queue Limit (AQL) To: =?UTF-8?B?VG9rZSBIw7hpbGFuZC1Kw7hyZ2Vuc2Vu?= Cc: Dave Taht , Rajkumar Manoharan , Kevin Hayes , Make-Wifi-fast , linux-wireless , Yibo Zhao , John Crispin , Johannes Berg , Lorenzo Bianconi , Felix Fietkau Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-List-Received-Date: Tue, 26 Nov 2019 05:04:37 -0000 > Yeah, bpftrace can be a bit of a pain to get running; but it may be > worth the investment longer term as well. It really is quite useful! :) My attempt to build bpftrace didn't work out, so I just got the sojourn time using old fashioned trace event. The raw trace, parsed data in csv format and plots can be found here: https://drive.google.com/open?id=3D1Mg_wHu7elYAdkXz4u--42qGCVE1nrILV All tests are done with 2 TCP download sessions that oversubscribed the link bandwidth. With AQL on, the mean sojourn time about ~20000us, matches the default codel "target". With AQL off, the mean sojourn time is less than 4us even the latency is off the charts, just as we expected that fd_codel with mac80211 alone is not effective for drivers with deep firmware/hardware queues. > Any chance you could turn ecn on and off and give it a go > again in your next test run? ECN on shows very similar results as with ECN off. "aqm" stats from debugfs shows it is doing ECN marking instead of dropping packets as expected. Flent test data also is in the same link. On Fri, Nov 22, 2019 at 2:45 AM Toke H=C3=B8iland-J=C3=B8rgensen wrote: > > Kan Yan writes: > > >> In theory, this ought to produce a histogram of sojourn times (in > >> microseconds): > >> bpftrace -e 'kretprobe:codel_skb_time_func { @sojourn =3D lhist((nsecs= - > > (retval << 10))/1000, 0, 100000, 1000); }' > > > > Thanks for the tips! > > > >> Can't get the CoDel drop mechanism to trigger on my system at all, > >> though (a laptop running on iwl). I guess because there's queue > >> backpressure to userspace first? > > > > What's the tcp_congestion_control in your system? Maybe it is BBR that > > prevents bufferbloat. > > It's not BBR, just plain old CUBIC. I've seen the issue before that it's > almost impossible to build a queue in the mac80211 layer when the TCP > session is originated on the local machine, though... > > >> It would be interesting to see if it works for you, assuming you can g= et > >> bpftrace to work on your test system :) > > > > I can enable required kernel configuration easily, but cross-compile > > bpftrace for an ARM64 platform may take some time and effort. > > Yeah, bpftrace can be a bit of a pain to get running; but it may be > worth the investment longer term as well. It really is quite useful! :) > > Some links: > > Install guide: > https://github.com/iovisor/bpftrace/blob/master/INSTALL.md > > Tutorial by one-liners: > https://github.com/iovisor/bpftrace/blob/master/docs/tutorial_one_liners.= md > > Reference guide: > https://github.com/iovisor/bpftrace/blob/master/docs/reference_guide.md#5= -tracepoint-static-tracing-kernel-level > > -Toke >