Increasing TCP listen backlog: www server

Robert Stockmann (
Mon, 31 Jul 1995 02:38:47 +0200 (MET DST)


I've been looking at the apache pages at, and from there
there are some interresting pages at about tuning
your server for high www load. First of all they mention to
use the netscape server.. Ok thats fine, but I want to use a P90
with Linux for www services. So I'm thinking about apache.

Second they mention to put the server as a standalone instead of
running it from inetd. Makes sense...

Third they say to "Increase the TCP listen backlog". This seems to
me a usefull tip. Its mentioned to replace in the source of webserver
the call's for listen(s,5) with listen(s,32) for instance...

In solaris there is a command for increasing the backlog for the system
by using the command:

/usr/sbin/ndd -set /dev/tcp tcp_conn_req_max 32

And the results are that on suns you'll find this:

R = 5 connections / 500 ms
= 10 connections/sec (Solaris 2.4 using default backlog)

R = 32 connections / 500 ms
= 64 connections/sec (Solaris 2.4 using increased backlog)

This is not bad..But when reading the manpages (man 2 listen) I read:

The backlog is currently limited (silently) to 5. [Docu-
menter's note: is this true for Linux?]

So whats the actual status of the listen() syscall right now for Linux??


|| R.M. Stockmann            ||   Delft University of Technology       ||
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