From owner-freebsd-questions@FreeBSD.ORG Sun Mar 26 16:40:23 2006 Return-Path: X-Original-To: freebsd-questions@freebsd.org Delivered-To: freebsd-questions@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id F244C16A432 for ; Sun, 26 Mar 2006 16:40:23 +0000 (UTC) (envelope-from list-freebsd-2004@morbius.sent.com) Received: from out4.smtp.messagingengine.com (out4.smtp.messagingengine.com [66.111.4.28]) by mx1.FreeBSD.org (Postfix) with ESMTP id C2F6F43D55 for ; Sun, 26 Mar 2006 16:40:14 +0000 (GMT) (envelope-from list-freebsd-2004@morbius.sent.com) Received: from frontend2.internal (frontend2.internal [10.202.2.151]) by frontend1.messagingengine.com (Postfix) with ESMTP id 5419AD42FD6 for ; Sun, 26 Mar 2006 11:40:13 -0500 (EST) Received: from frontend3.messagingengine.com ([10.202.2.152]) by frontend2.internal (MEProxy); Sun, 26 Mar 2006 11:39:59 -0500 X-Sasl-enc: HsmxFbPohlKSTyXVFr9zkOdIOrlBh+sVOF5ugIMrSWZs 1143391199 Received: from bb-87-81-140-128.ukonline.co.uk (bb-87-81-140-128.ukonline.co.uk [87.81.140.128]) by frontend3.messagingengine.com (Postfix) with ESMTP id 79AA5B97 for ; Sun, 26 Mar 2006 11:39:59 -0500 (EST) From: RW To: freebsd-questions@freebsd.org Date: Sun, 26 Mar 2006 17:39:59 +0100 User-Agent: KMail/1.9.1 References: <200603250209.10994.list-freebsd-2004@morbius.sent.com> <200603250237.31122.list-freebsd-2004@morbius.sent.com> <20060325162512.3ae2a4c5.wmoran@collaborativefusion.com> In-Reply-To: <20060325162512.3ae2a4c5.wmoran@collaborativefusion.com> MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200603261740.05369.list-freebsd-2004@morbius.sent.com> Subject: Re: TCP delayed acks not being delayed? X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 26 Mar 2006 16:40:24 -0000 On Saturday 25 March 2006 21:25, Bill Moran wrote: > Are you sure you're not exceeding the capability of the system to delay > acks? I would have thought not, it maxes-out with a receive space of 15k, and increasing the setting from 20k to 32k had no effect. > Besides, when you're transferring data in one > direction only, it doesn't make sense to delay empty acks. only on a > full-duplex transmissions do you get a benefit by taking measures to > ensure that all packets have data. When you're downloading, _all_ your > acks are empty, so who cares? I though I might be seeing a bug. I was only measuring it because I was thinking of switching to pf/altq and I wanted to know how much to allow for empty-acks. However, I hadn't done the arithmetic before, and I was surprized to see that 13% of my upload was being used. On a 4MB connection, that would be over half the bandwidth. Delayed acks don't affect the download speed on one tcp connection, but they could improve the performance of other traffic, when a download is taking place over a very asymmetric link. > Additionally, if the client application turns nagle off, this will > disable the use of delayed acks. For things like file transfer, it's > pretty much typical practice to disable nagle, I guess that explains it.