From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-x22a.google.com (mail-lf0-x22a.google.com [IPv6:2a00:1450:4010:c07::22a]) (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 AC7AB3CB41 for ; Sun, 22 Apr 2018 17:09:58 -0400 (EDT) Received: by mail-lf0-x22a.google.com with SMTP id j68-v6so11989374lfg.13 for ; Sun, 22 Apr 2018 14:09:58 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=79+UeEzrZ/jjws5bN4F5X1gPefm8yw9ENkj4qunvjrg=; b=sfGUvjgFbIvC/Fwkhgjw+NtSimd8uPZezo+BMRFEbuW9bBCz5IGobFblA0NhTA7S8g yMTEuALReSsWhTbbfPWW8R6YwKf9oF8Z0qSDQdOZSJs5c/mTZZfAc64MQgh1YqX8+se1 HlH0pg6HLF3DYWwhgE0yAt6PeWIVIQH0+Vv+1gFHXsv+eYNj3lX161R0SkPum2cFbcuV xtDU5eentvl8SHv5FO53cVb5Mzar0sl1bqIwRxGtDAhnaT3JOtPOPrLc2P3BVeWdGHl7 UQ+RKklz1bx8J/G4WtR6V4Gn1mSIYXcmqVJxGQTYg3jA2CyGyIkWWz5GhD6PP2E1vioX eoxA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=79+UeEzrZ/jjws5bN4F5X1gPefm8yw9ENkj4qunvjrg=; b=JBq9E+rV9l8JIaDGzY/gIMDNXbBwJoCKtc+yfTHwNXKDD+2bfHl2qH9NMxug8V2MBP r11NqKXIN282jvs9+VCmXgry61/V2RNeOJj/wspUkpwzLNIz084t5sJRzrzY0pLD4YPG QIOlSmecKY0EGaEkdFsqEaoPgX3k2SGsNQlTIW0vhXj2aTqW0DiWU8VuhSE75Z0/zfeN m+Tvd+q3JXVFIlxNJggl0ML/c+ksT/DRCXeA6euHnnEAN+r6PQlL7pfqoMF0pyAmpO9M BhFpx/nnXGlFcdRAm47Ge3Luvg5vc+aVZSQ62TV7rFC6nB4pV1h90oSuNc+8NCnVvONm IAKg== X-Gm-Message-State: ALQs6tAoe935yWYBrIu8aC5mI79nzmJM1UUbaOew+4ZdSvZ8jEJhvtBW zQKjp4ZNppPl4hbLC+8NTfo3MZGp X-Google-Smtp-Source: AIpwx48T6WPHHGUovuUe5n/35dB2mzIyQxnXABmO1djd8Irnw2GGN8RcLf0L3ZByJpSWhrihD37eqw== X-Received: by 10.46.48.22 with SMTP id w22mr6712474ljw.9.1524431397751; Sun, 22 Apr 2018 14:09:57 -0700 (PDT) Received: from [192.168.239.216] (83-245-234-255-nat-p.elisa-mobile.fi. [83.245.234.255]) by smtp.gmail.com with ESMTPSA id c89-v6sm2484309lfb.57.2018.04.22.14.09.56 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sun, 22 Apr 2018 14:09:57 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.3 \(3445.6.18\)) From: Jonathan Morton In-Reply-To: <87a7tv3r5z.fsf@toke.dk> Date: Mon, 23 Apr 2018 00:09:54 +0300 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <87a7tv3r5z.fsf@toke.dk> To: =?utf-8?Q?Toke_H=C3=B8iland-J=C3=B8rgensen?= X-Mailer: Apple Mail (2.3445.6.18) Subject: Re: [Cake] Testing variants of the MTU latency scaling X-BeenThere: cake@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Cake - FQ_codel the next generation List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 22 Apr 2018 21:10:00 -0000 > Takeaways (see attached plots): >=20 > - The MTU scaling does indeed give a nice benefit in egress mode > "tcp-download-totals" plot. =46rom just over 6 Mbps to just over 8 = Mbps > of goodput on the 10 Mbit link. There is not a large difference > between 2MTU and 4MTU, except that 4MTU hurts inter-flow latency > somewhat. >=20 > - The effect for upload flows (where Cake is before the bottleneck; > 10mbit-upload.png) is negligible. >=20 > - The MTU scaling really hurts TCP RTT (intra-flow latency; > tcp-upload-tcprtt-10mbit.png and rrul-tcprtt.png). >=20 > - For bidirectional traffic the combined effect is also negligible. >=20 >=20 > Based on all this, I propose we change the scaling mechanism so that = it > is only active in egress mode, and change it from 4 MTUs to 2. I'll > merge Kevin's patch to do this unless someone complains loudly :) >=20 > If you want me to run other tests, let me know. I'm not actually sure what you've measured here - unless you've somehow = managed to swap "ingress" with "egress" mode in a strange manner. I = don't see any systematic measurement of the different MTU scales in = ingress mode in your results, which makes your assertion that it should = only be active in egress mode rather odd. - Jonathan Morton