Re: SOMAXCONN - bump up or sysctl?

Andi Kleen (ak@suse.de)
13 Jul 2001 09:35:49 +0200


Tim Hockin <thockin@sun.com> writes:

> hey all,
>
> We have a request to bump up SOMAXCONN. Are there are repurcussions to
> doing so? Would it be better to make it a sysctl?

Have you checked if the requester is not satisfied with an increase
of /proc/sys/net/ipv4/tcp_max_syn_backlog? If they "know" from 2.0
that they want a SOMAXCONN increase then that's very likely the case.

In 2.2+ SOMAXCONN only applies to established sockets waiting to get
accept()ed; and when you have 128 established sockets that don't get served
by accept you have a big problem.

SYN-RECV sockets are a completely different thing and they are tuned
by the first sysctl and some other heuristics in 2.4.
You can also turn on syncookies there to handle syn-recv load spikes.

-Andi

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