linux-kernel - Re: What happened to CONFIG_TCP_NAGLE

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Message-ID: <456F34BE.5050303@cfl.rr.com>
Date:	Thu, 30 Nov 2006 14:45:02 -0500
From:	Phillip Susi <psusi@....rr.com>
To:	Matt Garman <matthew.garman@...il.com>
CC:	linux-kernel@...r.kernel.org
Subject: Re: What happened to CONFIG_TCP_NAGLE_OFF?

Matt Garman wrote:
> I don't want to change the API at all.  I'm using a closed-source, 3rd
> party library.  Using strace, I can see that the library does *not* do
> a setsockopt(...TCP_NODELAY...) on opened sockets.  Since I can't
> change the library, I would like to patch and/or configure my kernel
> so that all TCP/IP sockets default to TCP_NODELAY.

That _IS_ changing the api.  Applications that wish to use nagle will no 
longer be able to because you will have changed the api to always 
disable nagle.

> Also, if my understanding of Nagle is correct, I think you have that
> backwards: Nagle should be disabled (i.e. TCP_NODELAY) for telnet,
> mouse movements, etc: we always want to send our packets, regardless
> of size or previous packet ACK.

No, nagle was invented specifically for telnet.  Without nagle, every 
character you type is sent in its own packet, which gives around 50,000% 
overhead.  Nagle was created to compact most of your keystrokes into a 
single packet.

Things like mouse movements should not be sent over TCP at all.  UDP 
makes a much better protocol for that kind of data since if a packet is 
lost, there is no need to retransmit the same data; instead you just get 
the next position update and don't care about where the mouse was during 
the dropped packet.

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