From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x135.google.com (mail-lf1-x135.google.com [IPv6:2a00:1450:4864:20::135]) (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 A29ED3B2A4 for ; Sat, 7 Sep 2019 19:42:37 -0400 (EDT) Received: by mail-lf1-x135.google.com with SMTP id x80so7796033lff.3 for ; Sat, 07 Sep 2019 16:42:37 -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=nJOzS7HeqiCPRins7cD1zUp0SzR4t1xH+bN3mzOaykw=; b=nMCaEYIvlh7RbeGG/F3SKWrTRz3NCgMA3kXO0EJDaB2/3WL1iR1nK5DfdEGTesepQH mOMIPvMqmA+ZdBOqJFr/zz+3CdFV2ST/YgOOaEepevBfXwQEs3ognYUzanOgHGZGPBP/ PkhgfZQTjmkCm0trvp5lxG6DFr4bIaFN49yQqTN5DZ1FcSPSdhxsLKUGrm05zW8yuq8B Fe3KQGU/MBiheP756JL35zt6uFPli/A7usxLSDa3fS8pz4razKPeZpYu7KmTdThZvQW0 +YOYAppxul/z69k39Hg3C0DE93aZnt+sDphXHkGEBmHF0fiylcOYekquLsayypP4R9TB +kUw== 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=nJOzS7HeqiCPRins7cD1zUp0SzR4t1xH+bN3mzOaykw=; b=g85PQNaMONasZH7Zzkyopoe1BzHmq4J9LtrAjHHcF/+svqcHZqL2unFJD0Qge0rPth gdZPEEMTfCsr13boFaIFGZSsI4xkBIPF0aj10b+1JezffZrXS/xLYg+mjxNBJo03DGi7 ymhHT7vXjoI7m7XfxtQyGv0DNkTvC8b3meK2927N+dnAxwjIaAQGH8Dgmkhi/emgv1Ar +G8B7sehIysQ6PXwLTXLhshj4zAdDEqhzV7/pCBvUS+7PEEJgXFhO2wlZV1TaZOhyGRV kv6bylGb5bXYdgj9BQveXrI14EYTnDLzP7GmudxKjLZkYOxwRtX+JVR7e2vhYdRhrUSu P2tg== X-Gm-Message-State: APjAAAXApaWxST2XufOQks+1t58saYwkIIH20AUNBX067xKofDWjpiDT 9fDwmIqYEW3sSq7qfy2Ac2n8o/5gIGM= X-Google-Smtp-Source: APXvYqygS9SQI3EwQIDJLGFfk2q+7YbNk3oy3jOsBsPs5XdMzCmfKYofB/Y2lIWU+3sZn7s8nx7Slw== X-Received: by 2002:ac2:508b:: with SMTP id f11mr11477364lfm.153.1567899756641; Sat, 07 Sep 2019 16:42:36 -0700 (PDT) Received: from jonathartonsmbp.lan (83-245-237-193-nat-p.elisa-mobile.fi. [83.245.237.193]) by smtp.gmail.com with ESMTPSA id u21sm1710976lje.92.2019.09.07.16.42.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 07 Sep 2019 16:42:35 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 11.5 \(3445.9.1\)) From: Jonathan Morton In-Reply-To: <18b1c174-b88d-4664-9aa8-9c42925fc14c@www.fastmail.com> Date: Sun, 8 Sep 2019 02:42:34 +0300 Cc: cake@lists.bufferbloat.net Content-Transfer-Encoding: quoted-printable Message-Id: References: <2825CE14-2109-4580-A086-9701F4D3ADF0@gmail.com> <18b1c174-b88d-4664-9aa8-9c42925fc14c@www.fastmail.com> To: Justin Kilpatrick X-Mailer: Apple Mail (2.3445.9.1) Subject: Re: [Cake] Fighting bloat in the face of uncertinty 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: Sat, 07 Sep 2019 23:42:37 -0000 > On 8 Sep, 2019, at 2:31 am, Justin Kilpatrick = wrote: >=20 > If I set a throughput that's 50% too high should it still help? In my = testing it didn't seem to. In that case you would be relying on backpressure from the network = interface to cause queuing to actually occur in Cake rather than in the = driver or hardware (which would almost certainly be a dumb FIFO). If = the driver doesn't implement BQL, that would easily explain 300ms of = bloat. In fact I'm unsure as to why changing the AQM parameters would cure it. = You may have benefited from an unintentional second-order effect which = we normally try to eliminate, when the 'target' parameter gets too close = to the CPU scheduling latency of the kernel. I generally find it's better to *underestimate* the bandwidth parameter = by 50% than the reverse, simply to keep the queue out of the dumb = hardware. But if you want to try implementing BQL in the relevant = drivers, go ahead. - Jonathan Morton=