From owner-freebsd-stable@FreeBSD.ORG Thu Feb 18 16:18:33 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C7E52106566B for ; Thu, 18 Feb 2010 16:18:33 +0000 (UTC) (envelope-from shurd@sasktel.net) Received: from neutron.sasknet.sk.ca (neutron.sasknet.sk.ca [142.165.20.180]) by mx1.freebsd.org (Postfix) with ESMTP id 8D9EB8FC0A for ; Thu, 18 Feb 2010 16:18:33 +0000 (UTC) Received: from pps.filterd (neutron [127.0.0.1]) by neutron.sasknet.sk.ca (8.14.3/8.14.3) with SMTP id o1IGINlO013539 for ; Thu, 18 Feb 2010 10:18:32 -0600 Received: from bgmpomr1.sasknet.sk.ca (bgmpOMR1.sasknet.sk.ca [142.165.72.22]) by neutron.sasknet.sk.ca with ESMTP id m18ac2hm6-1 for ; Thu, 18 Feb 2010 10:18:32 -0600 Received: from ace.hurd.local (outgoing.bbsdev.net [76.202.204.46]) by bgmpomr1.sasknet.sk.ca (SaskTel eMessaging Service) with ESMTPA id <0KY100JJNPAVIC00@bgmpomr1.sasknet.sk.ca> for freebsd-stable@freebsd.org; Thu, 18 Feb 2010 10:18:32 -0600 (CST) Date: Thu, 18 Feb 2010 08:18:31 -0800 From: Stephen Hurd In-reply-to: <4B7D6635.20605@sasktel.net> To: Harald Schmalzbauer Message-id: <4B7D6857.80902@sasktel.net> MIME-version: 1.0 Content-type: text/plain; charset=ISO-8859-1; format=flowed Content-transfer-encoding: 7BIT References: <4B7C1365.9070806@omnilan.de> <70CD649D-7659-4CE2-A16C-49B8C891CB5B@mac.com> <4B7C4066.5040006@omnilan.de> <4B7D3938.1000309@omnilan.de> <4B7D5AC4.9020509@mahan.org> <4B7D61DE.2020906@omnilan.de> <4B7D6635.20605@sasktel.net> User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.8.1.23) Gecko/20091205 SeaMonkey/1.1.18 X-Proofpoint-Virus-Version: vendor=fsecure engine=1.12.8161:2.4.5, 1.2.40, 4.0.166 definitions=2010-02-18_10:2010-02-06, 2010-02-18, 2010-02-18 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=default score=0 spamscore=0 ipscore=0 phishscore=0 bulkscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx engine=5.0.0-0908210000 definitions=main-1002180112 Cc: freebsd-stable@freebsd.org, Patrick Mahan Subject: Re: RELENG_8 ignoring TCP window size? [Was: Re: Help for TCP understanding wanted, ACK-MSS-Window [Was: Re: best practice to watch TCP parms of established sockets]] X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Feb 2010 16:18:33 -0000 Stephen Hurd wrote: >> Some experimental results: >> When rsyncing with windows, and FreeBSD is receiver, I see the same >> ACK ever two segemnts, but speed is at 72MB/s. >> When FreeBSD is sender and Windows is receiver, it looks more I >> expected. There are about 20 data segments before a ACK is returned. >> And there are TCP Window Update Segments, reflecting smaller >> receiver buffers on the windows side. But this happens at a >> throughput of 82MB/s!!! So the windows machine is behaving like I >> understand the TCP flow control. >> Any explanation why the FreeBSD machine seems to ignore window size? > > The idea of delayed ACKs is to allow an ACK to be sent with data if > there will be data sent right away, not to combine ACKs... leaving out > ACKs makes calculation of RTT problematical which causes performance > problems all over the place... maybe the dearth of ACKs from the > windows system is causing the problem? If the problem is the ACKs from the Windows system, you should be seeing a large number of retransmits from the FreeBSD system (on the order of one retransmit per five packets). Is this what you're seeing? If you have a capture you could share covering a few seconds, I could take a look and provide a better opinion.