Date: Mon, 31 Dec 2001 16:43:00 -0800 (PST) From: Matthew Dillon <dillon@apollo.backplane.com> To: "Louis A. Mamakos" <louie@TransSys.COM> Cc: Julian Elischer <julian@elischer.org>, Terry Lambert <tlambert2@mindspring.com>, Mike Silbersack <silby@silby.com>, Josef Karthauser <joe@tao.org.uk>, Tomas Svensson <tsn@gbdev.net>, freebsd-hackers@FreeBSD.ORG Subject: Re: FreeBSD performing worse than Linux? Message-ID: <200201010043.g010h0i36281@apollo.backplane.com> References: <Pine.BSF.4.21.0112311225150.94344-100000@InterJet.elischer.org> <200112312327.fBVNRt719835@whizzo.transsys.com>
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: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
<dillon@backplane.com>
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