From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f67.google.com (mail-pg0-f67.google.com [74.125.83.67]) (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 35C243B29E; Mon, 25 Jun 2018 23:31:01 -0400 (EDT) Received: by mail-pg0-f67.google.com with SMTP id m5-v6so6986430pgd.3; Mon, 25 Jun 2018 20:31:01 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:date:message-id:in-reply-to :references:user-agent:subject:mime-version :content-transfer-encoding; bh=yPkALGB2nd2UXn6tHCIFjR/8N4NETtxvCKMNl7Ay2VY=; b=ucCDMPVCsxX0I85UTacqLtckDQivOlzjKp+xSG+ieHH6gj8wjh8JeBwe7ig1ONMwTz MhF0zsRoJE/0cO97IhKFsfCzem4/gMSyCaT3aNYi3F3AgyFvA9TrZ6SRSGzOO/gxsQaK UmtI/C8zJZmE3ye5X9NjE6Cr5ekajLlaXd2KYweIUk5YVmyxhbe81X723kWBY8mzL9kH 2HIXHRB5BaDTmEJf58ahdVsZFrtj4ziEGpmIMOH6YPT+1asOnvKZAyyn2AjiOH35kOWP 207KemvPlIiXpyFpeitinjCBCM3qC1nqMoOJMXMwCHIU5YUEhowiQiL8QMl0c5saXgbc GeEw== X-Gm-Message-State: APt69E2+zmVKAt0TBa4gotWtI+x4KL3mNxRx5KdfzH0EvTQAIysVGv+S nu3nVJ0jy++69KRcEemxQiI= X-Google-Smtp-Source: ADUXVKJweE8+5JU0rhPhdL1xT21PXPmrbGYpNX4w6xaWLo36LTInp+Ww+BfHw9xC3SlUDf2hc6aYOQ== X-Received: by 2002:a63:24c4:: with SMTP id k187-v6mr12740192pgk.434.1529983860194; Mon, 25 Jun 2018 20:31:00 -0700 (PDT) Received: from [100.99.231.234] (132.sub-174-215-0.myvzw.com. [174.215.0.132]) by smtp.gmail.com with ESMTPSA id m11-v6sm546163pgt.46.2018.06.25.20.30.58 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 25 Jun 2018 20:30:58 -0700 (PDT) From: Simon Barber To: Dave Taht , Jonathan Morton CC: bloat , "Make-Wifi-fast" Date: Mon, 25 Jun 2018 20:30:55 -0700 Message-ID: <1643a24e5b0.2786.e972a4f4d859b00521b2b659602cb2f9@superduper.net> In-Reply-To: References: <8736xgsdcp.fsf@toke.dk> <838b212e-7a8c-6139-1306-9e60bfda926b@gmail.com> <8f80b36b-ef81-eadc-6218-350132f4d56a@pollere.com> <9dbb8dc8-bec6-8252-c063-ff0ba5fd7c1a@pollere.com> <25305.1529678986@localhost> <47EC21F5-94D2-4982-B0BE-FA1FA30E7C88@gmail.com> <18224.1529704505@localhost> <87muvjnobj.fsf@toke.dk> <68C3BBE1-96DA-41F7-9878-582074C4E769@gmail.com> <642CBFAE-A182-4D6E-968B-411159CBFD9B@superduper.net> <422BFE8C-1AAC-4A55-AF1F-448B3B5C0E28@gmail.com> User-Agent: AquaMail/1.15.0-916 (build: 101500003) MIME-Version: 1.0 Content-Type: text/plain; format=flowed; charset="UTF-8" Content-Transfer-Encoding: 8bit Subject: Re: [Bloat] lwn.net's tcp small queues vs wifi aggregation solved X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Jun 2018 03:31:01 -0000 Current versions of Wireshark have an experimental feature I added to expose airtime usage per packet and show 802.11 pcaps on a timeline. Enable it under Preferences->Protocol->802.11 Radio Simon On June 25, 2018 6:27:59 PM Dave Taht wrote: > On Mon, Jun 25, 2018 at 5:44 PM, Jonathan Morton wrote: >>> On 26 Jun, 2018, at 3:36 am, Simon Barber wrote: >>> >>> Most hardware needs the packet finalized before it starts to contend for >>> the medium (as far as I’m aware - let me know if you know differently). One >>> issue is that if RTS/CTS is in use, then the packet duration needs to be >>> known in advance (or at least mid point of the RTS transmission). >> >> This is a valid argument. I think we could successfully argue for a delay >> of 1ms, if there isn't already enough data in the queue to fill an >> aggregate, after the oldest packet arrives until a request is issued. > > Whoa, nelly! In the context of the local tcp stack over wifi, I was > making an observation that I "frequently" saw a pattern of a single > ack txop followed by a bunch in a separate txop. and I suggested a > very short (10us) timeout before committing to the hw - not 1ms. > > Aside from this anecdote we have not got real data or statistics. The > closest thing I have to a tool that can take apart wireless aircaps is > here: https://github.com/dtaht/airtime-pie-chart which can be hacked > to take more things apart than it currently does. Looking for this > pattern in more traffic would be revealing in multiple ways. Looking > for more patterns in bigger wifi networks would be good also. > > I like erics suggestion of doing more ack compression higher up in the > tcp stack. > > There are two other things I've suggested in the past we look at. 1) > The current fq_codel_for_wifi code has a philosophy of "one aggregate > in the hardware, one ready to go". A simpler modification to fit more > in would be to (wait the best case estimate for delivering the one in > the hardware - a bit), then form the one ready-to-go. > > 2) rate limiting mcast and smoothing mcast bursts over time, allowing > more unicast through. presently the mcast queue is infinite and very > bursty. 802.11 std actually suggests mcast be rate limited by htb, > where I'd be htb + fq + merging dup packets. I was routinely able to > blow up the c.h.i.p's wifi and the babel protocol by flooding it with > mcast, as the local mcast queue could easily grow 16+ seconds long. > > um, I'm giving a preso tomorrow and will run behind this thread. It's > nice to see the renewed enthusiasm here, keep it up. > >>> If there are no other stations competing for airtime, why does it matter >>> that we use two txops? >> >> One further argument would be power consumption. Radio transmitters eat >> batteries for lunch; the only consistently worse offender I can think of is >> a display backlight, assuming the software is efficient. > >> - Jonathan Morton >> >> _______________________________________________ >> Bloat mailing list >> Bloat@lists.bufferbloat.net >> https://lists.bufferbloat.net/listinfo/bloat > > > > -- > > Dave Täht > CEO, TekLibre, LLC > http://www.teklibre.com > Tel: 1-669-226-2619 Sent with AquaMail for Android https://www.mobisystems.com/aqua-mail