From owner-freebsd-hackers Mon Dec 31 16:43:13 2001 Delivered-To: freebsd-hackers@freebsd.org Received: from apollo.backplane.com (apollo.backplane.com [216.240.41.2]) by hub.freebsd.org (Postfix) with ESMTP id 7E46A37B417 for ; Mon, 31 Dec 2001 16:43:09 -0800 (PST) Received: (from dillon@localhost) by apollo.backplane.com (8.11.6/8.9.1) id g010h0i36281; Mon, 31 Dec 2001 16:43:00 -0800 (PST) (envelope-from dillon) Date: Mon, 31 Dec 2001 16:43:00 -0800 (PST) From: Matthew Dillon Message-Id: <200201010043.g010h0i36281@apollo.backplane.com> To: "Louis A. Mamakos" Cc: Julian Elischer , Terry Lambert , Mike Silbersack , Josef Karthauser , Tomas Svensson , freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD performing worse than Linux? References: <200112312327.fBVNRt719835@whizzo.transsys.com> 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 :An underlying issue here is why applications decide to set TCP_NODELAY :options on sockets, rather than just letting Nagle's algorithm do :the right thing. I recall some handwaving about this in the X server :some years ago to make mouse movements "smoother". : :For the problem at hand, if both the client and server machines didn't :do TCP_NODLEAY, then there'd only be one packet smaller than the :TCP MSS in flight between the transmitter and receiver at any one :time. I think that poking OpenSSH to not set the TCP_NODELAY option :"fixed" this problem. : :I was just pondering the TCP implementation in 4.5-PRERELEASE, and :it doesn't look like there's any explicit delay after a write going :on, other than Nagle's algorithm, in the TCP packetization code. So :setting TCP_NODELAY is almost certain the Wrong Thing for most :applications to do. Perhaps there ought to be a warning in the :man page about being a poor network citizen, flooding the Internet :with tinygrams and otherwise making the performance of your application :generally suck. : :louie Yes, you are correct. There is no real reason for ssh to set TCP_NODELAY on FreeBSD and, in fact, I believe it didn't used to. We should just turn it off. -Matt Matthew Dillon To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message