From owner-freebsd-net Thu Oct 31 19: 1:33 2002 Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 8D15A37B401 for ; Thu, 31 Oct 2002 19:01:32 -0800 (PST) Received: from thunderer.cnchost.com (thunderer.concentric.net [207.155.252.72]) by mx1.FreeBSD.org (Postfix) with ESMTP id 22B9F43E3B for ; Thu, 31 Oct 2002 19:01:32 -0800 (PST) (envelope-from bakul@bitblocks.com) Received: from bitblocks.com (adsl-209-204-185-216.sonic.net [209.204.185.216]) by thunderer.cnchost.com id WAA03036; Thu, 31 Oct 2002 22:01:30 -0500 (EST) [ConcentricHost SMTP Relay 1.15] Message-ID: <200211010301.WAA03036@thunderer.cnchost.com> To: Fran.Lawas-Grodek@grc.nasa.gov, Cindy.Tran@grc.nasa.gov Cc: freebsd-net@FreeBSD.ORG, Mark.Allman@grc.nasa.gov Subject: Re: Problem in High Speed and Long Delay with FreeBSD In-reply-to: Your message of "Thu, 31 Oct 2002 13:56:01 EST." <20021031135601.B23802@grc.nasa.gov> Date: Thu, 31 Oct 2002 19:01:30 -0800 From: Bakul Shah Sender: owner-freebsd-net@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.org > Testing commands used: > receiver> ttcp -b 312500 -l 1024 -r -s > sender> ttcp -b 312500 -l 1024 -n 100000 -s -t receiverhost Pure speculation: Since you are writing 1K at a time, could it be an N^2 effect while appending mbufs? Since you can have many MBs in the pipe due to large delay*BW, you can potentially have many many mbufs. The Nth write will have to traverse O(N) mbuf chains to append the new data. One way to test is to increase the -l parameter value to something large and see if the throughput improves. If this is the case, FreeBSD will have to optimize this common case for stream protocols. Note that I haven't even looked at the relevant FreeBSD code! For all I know it may already be doing this. -- bakul To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message