From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from rn-mailsvcp-ppex-lapp24.apple.com (rn-mailsvcp-ppex-lapp24.rno.apple.com [17.179.253.38]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id C41A33B2A4 for ; Tue, 5 Oct 2021 12:19:01 -0400 (EDT) Received: from pps.filterd (rn-mailsvcp-ppex-lapp24.rno.apple.com [127.0.0.1]) by rn-mailsvcp-ppex-lapp24.rno.apple.com (8.16.1.2/8.16.1.2) with SMTP id 195GD8tN020706; Tue, 5 Oct 2021 09:18:57 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=apple.com; h=date : from : to : cc : subject : message-id : references : mime-version : content-type : in-reply-to; s=20180706; bh=aJX7f/4T16MtoLXof/Xypw07DDeAj4b6RnPQNGnOBgI=; b=j7RcgjXwoKEq9TsTInq0nSdFwHn1bYnQys6IFxK6SDfOlQjBAvGYakYFN0JhQwPKn95Y TJtAwnRyFt6iNV4Ud+GwRJOvZpouEZrv8xrv5MxE+ZQwJBjjM9r5VklwQs/mrS0OhrfD UeZORFIg3mB4kpRt4NJzpLgNnuVG8WC18V2EuOPfmlOaj2vaULEvCYDMd+4TAy5QjJ+W S0L+KStKLKPDJIFOu3F1U6cB0JUZR15bK1KDgSW2XPx/1Nx/3USDDqRq++gaCE+G9tcQ 6quEywJqRCVKHBAmIsyaU/C/LsxbMluoTbhO1eow65MFF3XMz2VDH12Himpcw9knuaGr GQ== Received: from rn-mailsvcp-mta-lapp01.rno.apple.com (rn-mailsvcp-mta-lapp01.rno.apple.com [10.225.203.149]) by rn-mailsvcp-ppex-lapp24.rno.apple.com with ESMTP id 3ben19h6v5-4 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO); Tue, 05 Oct 2021 09:18:57 -0700 Received: from rn-mailsvcp-mmp-lapp03.rno.apple.com (rn-mailsvcp-mmp-lapp03.rno.apple.com [17.179.253.16]) by rn-mailsvcp-mta-lapp01.rno.apple.com (Oracle Communications Messaging Server 8.1.0.9.20210415 64bit (built Apr 15 2021)) with ESMTPS id <0R0I00LCGINKPMD0@rn-mailsvcp-mta-lapp01.rno.apple.com>; Tue, 05 Oct 2021 09:18:56 -0700 (PDT) Received: from process_milters-daemon.rn-mailsvcp-mmp-lapp03.rno.apple.com by rn-mailsvcp-mmp-lapp03.rno.apple.com (Oracle Communications Messaging Server 8.1.0.9.20210415 64bit (built Apr 15 2021)) id <0R0I00500IME7S00@rn-mailsvcp-mmp-lapp03.rno.apple.com>; Tue, 05 Oct 2021 09:18:56 -0700 (PDT) X-Va-A: X-Va-T-CD: 0784ebc13a2136f668ccea2ff57975fe X-Va-E-CD: 6f6db8dfccb605e874e868c0e85c5b24 X-Va-R-CD: 28e1937a51efda83d95d1b6b410d69e6 X-Va-CD: 0 X-Va-ID: 920164a9-a054-4eba-b23d-67cbf3d12b76 X-V-A: X-V-T-CD: 0784ebc13a2136f668ccea2ff57975fe X-V-E-CD: 6f6db8dfccb605e874e868c0e85c5b24 X-V-R-CD: 28e1937a51efda83d95d1b6b410d69e6 X-V-CD: 0 X-V-ID: 4643443d-37de-4080-afe3-bb759c9cc4cd X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-10-05_03:2021-10-04, 2021-10-05 signatures=0 Received: from localhost ([17.192.155.152]) by rn-mailsvcp-mmp-lapp03.rno.apple.com (Oracle Communications Messaging Server 8.1.0.9.20210415 64bit (built Apr 15 2021)) with ESMTPSA id <0R0I00XCQINJMU00@rn-mailsvcp-mmp-lapp03.rno.apple.com>; Tue, 05 Oct 2021 09:18:55 -0700 (PDT) Date: Tue, 05 Oct 2021 09:18:55 -0700 From: Christoph Paasch To: Matt Mathis Cc: Rpm Message-id: References: MIME-version: 1.0 Content-type: text/plain; charset=us-ascii Content-disposition: inline In-reply-to: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391, 18.0.790 definitions=2021-10-05_02:2021-10-04, 2021-10-05 signatures=0 Subject: Re: [Rpm] Outch! I found a problem with responsiveness X-BeenThere: rpm@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: revolutions per minute - a new metric for measuring responsiveness List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 05 Oct 2021 16:19:01 -0000 Hello Matt, On 10/04/21 - 16:23, Matt Mathis via Rpm wrote: > It has a super Heisenberg problem, to the point where it is unlikely to > have much predictive value under conditions that are different from the > measurement itself. The problem comes from the unbound specification for > "under load" and the impact of the varying drop/mark rate changing the > number of rounds needed to complete a transaction, such as a page load. this is absolutely right. This is why it is not just "Responsiveness", but "Responsiveness under working conditions" and it is important to specify the "working conditions" properly. They need to be using a "realistic" workload, while at the same time exploring the boundaries. This is why we chose a set of HTTP/2 bulk data-transfers, using standard congestion controls. > For modern TCP on an otherwise unloaded link with any minimally correct > queue management (including drop tail), the page load time is insensitive > to the details of the queue management. There will be a little bit of > link idle in the first few RTT (early slowstart), and then under a huge > range of conditions for both the web page and the AQM, TCP will maintain at > least a short queue at the bottleneck with zero idle, up until the last > segment is delivered, TCP will also avoid sending any duplicate data, so > the total data sent will be determined by the total number of bytes in the > page, and the total elapsed time, by the page size and link rate (plus the > idle from startup). > > If AQM is used to increase the responsiveness, the losses or ECN marks will > cause the browser to take additional RTTs to load the page. If there is no > cross traffic, these two effects (more rounds at higher RPM) will exactly > counterbalance each other. > > This is perhaps why there are BB deniers: for many simple tasks it has zero > impact. That's right. BB is a transient problem that is extremely short-lived. Having tried for the past year to reliably demo the user-visible impact of bufferbloat, I have learned two things: 1. When it happens, it is bad - really bad. 2. However, it is very difficult to trigger it "on-demand". > A concrete definition for "under load" should help to compare metrics > between implementations, but may not help predicting application > performance. "Responsiveness under working conditions" is a metric similar to throughput measured by tools like speedtest. Sure, speedtest may measure close to 1Gbps on my home-network, but that does not mean that I am able to actually send my emails at 1Gbps. The same is true for responsiveness. It pushes the network to its limit and explores the capabilities at that point. Talk to you soon! Cheers, Christoph