From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lb0-x22a.google.com (mail-lb0-x22a.google.com [IPv6:2a00:1450:4010:c04::22a]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by huchra.bufferbloat.net (Postfix) with ESMTPS id 8D1B721F3F7 for ; Thu, 16 Apr 2015 06:25:50 -0700 (PDT) Received: by lbcga7 with SMTP id ga7so58619795lbc.1 for ; Thu, 16 Apr 2015 06:25:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=content-type:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=ys5D5Rcq2dTQeJdtwOcfABVCzDdHtasifk2b1WTiAzE=; b=sifVuGZKO0pTzW0OCO1yqEr+RBCKIPVBvuRijA0txm9MsGebvgaqIsm+ScZKv1HyJf IglAuXZ0KqTzZmPp1bCG84pJl+fE3LjDs7/+cWqMD0/ORlVusdF/kfvSF7+m3iaY+c7G a12iYUR3ntbfxPG3pGy6kC/SwflgAreysDn42m7EHZ0CXt4QbchtTBqkRxyz07O3LCmG hNWD1uB0Blh8XKTWlN7zSXmlMYg6lBLV7Ewp90+A1B9Roq4omBdTmIRhMIkHQkYeDgFx qnBneHZg+CpeqU3SrWTCqThtUVAIfkfnHoL7F/C+KaSFHXAcQ/pq6NZSvTaTtsbeDt3B Buow== X-Received: by 10.112.139.130 with SMTP id qy2mr22297991lbb.33.1429190747494; Thu, 16 Apr 2015 06:25:47 -0700 (PDT) Received: from [192.168.43.25] (37-219-85-148.nat.bb.dnainternet.fi. [37.219.85.148]) by mx.google.com with ESMTPSA id up8sm1687553lbb.27.2015.04.16.06.25.45 (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Thu, 16 Apr 2015 06:25:46 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 8.2 \(2098\)) From: Jonathan Morton In-Reply-To: Date: Thu, 16 Apr 2015 16:25:41 +0300 Content-Transfer-Encoding: quoted-printable Message-Id: <5BC1CA30-289D-42B4-95CD-3AE5D7B96F09@gmail.com> References: To: Adrian Popescu X-Mailer: Apple Mail (2.2098) Cc: cake@lists.bufferbloat.net Subject: Re: [Cake] Cake3 - source code and some questions X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 16 Apr 2015 13:26:19 -0000 > On 16 Apr, 2015, at 15:14, Adrian Popescu = wrote: >=20 > Will the changes to codel made by cake be put into fq_codel? This might be a more complex question than you realise. The most likely feature of cake to be implemented in fq_codel might be = the set-associative hash, since it=E2=80=99s almost a pure win. That = would almost be a cut-and-paste operation, but due to fq_codel=E2=80=99s = de-facto status as a =E2=80=9Cstandard candle=E2=80=9D in research, it = would need to be made configurable, at least to make turning it off = easy. And that isn=E2=80=99t really a =E2=80=9Ccodel=E2=80=9D feature = change, since it influences the FQ layer exclusively. The codel parameter tuning done by cake isn=E2=80=99t applicable to = fq_codel, because the bandwidth information that this tuning relies on = isn=E2=80=99t available (not even when it=E2=80=99s stacked with HTB). = That=E2=80=99s why cake defaults to something very like the standard = codel parameters when the internal shaper is disabled (=E2=80=9Cunlimited=E2= =80=9D mode), and that in turn is one reason why those defaults are also = used at "sufficiently high=E2=80=9D bandwidths, so that there isn=E2=80=99= t a sharp discontinuity in the behaviour when the bandwidth is increased = beyond the link rate and on to infinity (unlimited mode actually works = by setting the shaper to infinite bandwidth, ie. zero time per byte). = The other reason, as I previously noted, is because the parameters = depend on the total RTT as well as the packet rate. Which leaves algorithmic changes to codel itself. It=E2=80=99s = certainly possible to drop these (fairly subtle) changes in, but we = should probably spend some more time measuring the effects of these = changes and finalising them. We=E2=80=99re considering doing a major = refactor of the code, which might make it harder to perform a drop-in = replacement. In any case, FQ does mean that codel=E2=80=99s precise = behaviour is less critical than it might otherwise be, and there are = valid arguments - such as the =E2=80=9Cstandard candle=E2=80=9D one - = for leaving it alone. - Jonathan Morton