SOMAXCONN - bump up or sysctl?
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Quoted 4 lines · Tim Hockin
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