From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x136.google.com (mail-lf1-x136.google.com [IPv6:2a00:1450:4864:20::136]) (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 641103B29E for ; Tue, 18 Oct 2022 13:03:36 -0400 (EDT) Received: by mail-lf1-x136.google.com with SMTP id j4so23710789lfk.0 for ; Tue, 18 Oct 2022 10:03:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=broadcom.com; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=cmZmaPeNyV4VLRDBix3Fw5BirUSq3UlGzvkqGyv0lv0=; b=PBOk/OZatltiWUegUZF2KZpuloyyZB7QNFd0sF5PswIHyKmdjQn3u1bZ+IzDoaDT7C QUu50FQmIhYaEGe47dBkR3fMGdyOcUEvyJkjPPTLnNwYsz9Qi1pvwiEuGDtwmbG/1JBn +OaqnjC4EC1IFN3Njhi/59mp6Hul+vxmr+mck= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=cmZmaPeNyV4VLRDBix3Fw5BirUSq3UlGzvkqGyv0lv0=; b=Eh1Azcd9D+Lr6dcrF70vhcz1xH9JIQ8MrpNaSFmEsSwXwm7cLBhx0h/q9aYRG2Itkh HuR5PiQ5Fybzn5/tB9HQKpXSc1ebcOV+q6Y99TE5AxMAqwUiCj5X0F7VgR1+JEd+ff8X 9cPPnEfxUk+CFSx/BNHg/ASklvcEZIBus1pge94sXjL4cU6T9i6yQWkBZ3py9gPR/zVN svOI4nBF3z3pGCOqGJF2Tg8kgCi+biAxwZ+eKGHkH2CnLVFcP7up4H8nUphL7aA9loXO Jsc90VRRrqAy2TqKHdbLnoI+0RHnEb6swa5fWUAWwdzkUuz7ruj4IFnr7aCdLpi7LKLr tRig== X-Gm-Message-State: ACrzQf2uUrYqWFQch5FbeuPmmHB5P+0DN+DrsREXbqU6TMIMYKKKvitK lTBjekreQlkEqmeKjwbYvYYzp5qPbcZ19n+/TtKl4XwkfJHZDmFF3NaNZ8Bkq/NDfdaEpahAQTs YXdj6mAq/q2RQlbKuC7rJXIkd+Ou0FGsBgIXIlDPyFQ== X-Google-Smtp-Source: AMsMyM6ydoUMvIPzf1JU0Il95ia1EiYhyX1oTcXc4GkAaNIdOGrIecMsdJbxDXfEV7jXnC0QmhuWwVBc1kdYAO1gZzA= X-Received: by 2002:a05:6512:533:b0:4a2:f36:bba5 with SMTP id o19-20020a056512053300b004a20f36bba5mr1287896lfc.224.1666112614871; Tue, 18 Oct 2022 10:03:34 -0700 (PDT) MIME-Version: 1.0 References: <938D9D45-DADA-4291-BD8A-84E4257CEE49@apple.com> <6710sq51-1151-s739-qq87-0r5264qrs9q8@ynat.uz> In-Reply-To: <6710sq51-1151-s739-qq87-0r5264qrs9q8@ynat.uz> From: Bob McMahon Date: Tue, 18 Oct 2022 10:03:21 -0700 Message-ID: To: David Lang Cc: Dave Taht , Rpm , Cake List , bloat , Make-Wifi-fast Content-Type: multipart/alternative; boundary="00000000000090d96205eb521240" Subject: Re: [Make-wifi-fast] [Bloat] The most wonderful video ever about bufferbloat 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, 18 Oct 2022 17:03:36 -0000 --00000000000090d96205eb521240 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable I agree with Stuart that there is no reason for shared lines in the first place. It seems like a design flaw to have a common queue that congests in a way that impacts the one transmit unit as the atomic forwarding plane unit. The goal of virtual output queueing is to eliminate head of line blocking, every egress transmit unit gets its own cashier with no competition. The VOQ queue depths should support one transmit unit and any jitter through the switching subsystem - jitter for the case of non-bloat and where a faster VOQ service rate can drain the VOQ. If the VOQ can't be drained per a faster service rate, then it's just one transmit unit as the queue is now just a standing queue w/delay and no benefit. Many network engineers typically, though incorrectly, perceive a transmit unit as one ethernet packet. With WiFi it's one Mu transmission or one Su transmission, with aggregation(s), which is a lot more than one ethernet packet but it depends on things like MCS, spatial stream powers, Mu peers, etc. and is variable. Some data center designs have optimized the forwarding plane for flow completion times so their equivalent transmit unit is a mouse flow. I perceive applying AQM to shared queue congestion as a mitigation technique to a poorly designed forwarding plane. The hope is that transistor engineers don't do this and "design out the lines" from the beginning. Better switching engineering vs queue management applied afterwards as a mitigation technique. Bob On Mon, Oct 17, 2022 at 7:58 PM David Lang via Make-wifi-fast < make-wifi-fast@lists.bufferbloat.net> wrote: > On Mon, 17 Oct 2022, Dave Taht via Bloat wrote: > > > On Mon, Oct 17, 2022 at 5:02 PM Stuart Cheshire > wrote: > >> > >> On 9 Oct 2022, at 06:14, Dave Taht via Make-wifi-fast < > make-wifi-fast@lists.bufferbloat.net> wrote: > >> > >> > This was so massively well done, I cried. Does anyone know how to ge= t > in touch with the ifxit folk? > >> > > >> > https://www.youtube.com/watch?v=3DUICh3ScfNWI > >> > >> I=E2=80=99m surprised that you liked this video. It seems to me that i= t repeats > all the standard misinformation. The analogy they use is the standard > terrible example of waiting in a long line at a grocery store, and the > =E2=80=9Csolution=E2=80=9D is letting certain traffic =E2=80=9Cjump the l= ine, angering everyone > behind them=E2=80=9D. > > > > Accuracy be damned. The analogy to common experience resonates more. > > actually, fair queueing is more like the '15 items or less' lanes to spee= d > through the people doing simple things rather than having them wait behin= d > the > mother of 7 doing their monthly shopping. > > David Lang_______________________________________________ > Make-wifi-fast mailing list > Make-wifi-fast@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/make-wifi-fast --=20 This electronic communication and the information and any files transmitted= =20 with it, or attached to it, are confidential and are intended solely for=20 the use of the individual or entity to whom it is addressed and may contain= =20 information that is confidential, legally privileged, protected by privacy= =20 laws, or otherwise restricted from disclosure to anyone else. If you are=20 not the intended recipient or the person responsible for delivering the=20 e-mail to the intended recipient, you are hereby notified that any use,=20 copying, distributing, dissemination, forwarding, printing, or copying of= =20 this e-mail is strictly prohibited. If you received this e-mail in error,= =20 please return the e-mail to the sender, delete it from your computer, and= =20 destroy any printed copy of it. --00000000000090d96205eb521240 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
I agree with Stuart that there is no reason for shared lin= es in the first place. It seems like a design flaw to have a common queue t= hat congests in a way that impacts the one transmit unit as the atomic forw= arding plane unit.=C2=A0=C2=A0The goal of=C2=A0virtual output queueing=C2=A0is t= o eliminate head of line blocking, every egress transmit unit gets its own = cashier with no competition.=C2=A0 The VOQ queue depths should support one = transmit unit and any jitter through the switching subsystem - jitter for t= he case of non-bloat and where a faster=C2=A0VOQ service rate can drain the= VOQ.=C2=A0 If the VOQ can't be drained per a faster service rate, then= it's just one transmit=C2=A0unit as the queue is now just a standing q= ueue w/delay and no benefit.

Many network engineers typically, thoug= h incorrectly, perceive a transmit unit as one ethernet packet. With WiFi i= t's one Mu transmission or one Su transmission, with aggregation(s), wh= ich is a lot more than one ethernet packet but it depends on things like MC= S, spatial stream powers, Mu peers, etc. and is variable. Some data center = designs have optimized the forwarding plane for flow completion times so th= eir equivalent transmit unit is a mouse flow.

I perceive applying AQ= M to shared queue congestion as a mitigation technique to a poorly designed= forwarding plane. The hope is that transistor engineers don't do this = and "design out the lines" from the beginning. Better switching e= ngineering vs queue=C2=A0management applied afterwards as a mitigation tech= nique.

Bob

On Mon, Oct 17, 2022 at 7:58 PM David Lang via Make-wifi-f= ast <make-wifi-f= ast@lists.bufferbloat.net> wrote:
On Mon, 17 Oct 2022, Dave Taht via Bloat wrote:
> On Mon, Oct 17, 2022 at 5:02 PM Stuart Cheshire <cheshire@apple.com> wrote:
>>
>> On 9 Oct 2022, at 06:14, Dave Taht via Make-wifi-fast <make-wif= i-fast@lists.bufferbloat.net> wrote:
>>
>> > This was so massively well done, I cried. Does anyone know ho= w to get in touch with the ifxit folk?
>> >
>> > https://www.youtube.com/watch?v=3DUICh3Sc= fNWI
>>
>> I=E2=80=99m surprised that you liked this video. It seems to me th= at it repeats all the standard misinformation. The analogy they use is the = standard terrible example of waiting in a long line at a grocery store, and= the =E2=80=9Csolution=E2=80=9D is letting certain traffic =E2=80=9Cjump th= e line, angering everyone behind them=E2=80=9D.
>
> Accuracy be damned. The analogy to common experience resonates more.
actually, fair queueing is more like the '15 items or less' lanes t= o speed
through the people doing simple things rather than having them wait behind = the
mother of 7 doing their monthly shopping.

David Lang_______________________________________________
Make-wifi-fast mailing list
M= ake-wifi-fast@lists.bufferbloat.net
https://lists.bufferbloat.net/listinfo/make-wif= i-fast

This ele= ctronic communication and the information and any files transmitted with it= , or attached to it, are confidential and are intended solely for the use o= f the individual or entity to whom it is addressed and may contain informat= ion that is confidential, legally privileged, protected by privacy laws, or= otherwise restricted from disclosure to anyone else. If you are not the in= tended recipient or the person responsible for delivering the e-mail to the= intended recipient, you are hereby notified that any use, copying, distrib= uting, dissemination, forwarding, printing, or copying of this e-mail is st= rictly prohibited. If you received this e-mail in error, please return the = e-mail to the sender, delete it from your computer, and destroy any printed= copy of it. --00000000000090d96205eb521240--