From owner-freebsd-hackers Fri Nov 30 9:53:19 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from exuma.irbs.com (exuma.irbs.com [216.86.160.252]) by hub.freebsd.org (Postfix) with ESMTP id B3B5037B419; Fri, 30 Nov 2001 09:53:16 -0800 (PST) Received: by exuma.irbs.com (Postfix, from userid 2500) id C9F6E17406; Fri, 30 Nov 2001 12:53:10 -0500 (EST) Date: Fri, 30 Nov 2001 12:53:10 -0500 From: John Capo To: babkin@freebsd.org Cc: jc@irbs.com, freebsd-hackers@freebsd.org Subject: Re: FreeBSD performing worse than Linux? Message-ID: <20011130125310.A3538@exuma.irbs.com> Reply-To: jc@irbs.com References: <20011128153817.T61580@monorchid.lemis.com> <15364.38174.938500.946169@caddis.yogotech.com> <20011129004234.A16101@exuma.irbs.com> <3C0707BD.B8FA31F8@bellatlantic.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2i In-Reply-To: <3C0707BD.B8FA31F8@bellatlantic.net>; from babkin@bellatlantic.net on Thu, Nov 29, 2001 at 11:14:53PM -0500 Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG Looking at the complete dump on the server more closely I see what's happening. The server didn't jump ahead in the stream. The client side of these tests is on a fractional T1. In about 60Ms the server pushed a window's worth of data, about 200 packets since the payload was small, 48 bytes. (48 + IP + TCP) * 200 is around 17KB in 60Ms which overflowed the frame switch queue. The other part of the dump where the server is acked for a segment just sent but does not send the next segment till a duplicate ack is received better than a second later is still suspect to me. John Capo Quoting Sergey Babkin (babkin@bellatlantic.net): > > And here a _very_ pathological thing has happened: the server > just forgot to send the data between sequence numbers 12937 > and 28049. Since the dump was done on the server side, this suggests > that something very bad has happened with the TCP state on > the server side. Possibly the value of the current sequence number > in the protocol control block got overwritten by something. > To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message