sysctl kern.ipc.somaxconn limit 65535 why?

Hi everyone.

Actually 65k sockets is incredibly easy to reach.

I manage some servers for a very large website, it currently has several
http servers clustered to handle daily traffic and this is only dynamic
content, static has its own servers, databases also have own servers.

We recently started using memcached to cache some queries and we found on
default server limits sockets were saturated extremely quickly, on the linux
servers bumping it to a few hundred K solved the issue, wasnt possible on
bsd.  We did manage to get it down to only needing about 20k by setting
extremely low timeout values.

In addition we had to migrate all our mysql servers from freebsd to debian
because they were hitting some arbitary OS limit but I could never figure
out what, sys% usage went through the roof when this limit was hit, issue
didnt occur on debian.  I feel recently freebsd is more focused on desktop's
and as such developer's never develop for a heavy server usage scenario, and
I keep coming across hardcoded low limits.  As rightly pointed out default
values now days are useless 128 for somaxconn? maybe ok for a desktop.

Freebsd also has issues with high numbers of cpu cores, very high locking
overheads,  the problem is the modern hardware is focusing on more and more
cores and as such much more work on a server so a OS has to handle more and
more processing and data, this includes more bigger connection queues and so
on.  FreeBSD just isnt scaling with more powerful hardware.  Also forgetting
as well DDOS attack scenarios where a high queue size is useful.

I have used FreeBSD since the 4.x days and have been forced to migrate OS on
several servers as FreeBSD to be blunt couldnt handle the load on those
servers.  It does seem as if developers of the OS are getting out of touch
in respect to modern hosting enviromnents.  I cant tell app developers to
fix their apps to work on FreeBSD, they dont care, if it works fine on
windows and linux then the app isnt broken as far as they are concerned.
The more FreeBSD dev's have this aatitude of not adapting the less machines
will run the OS.  I hate many things about debian but at the end of the day
I have to use what can handle the load or I lose my job.

I do accept its entirely possible some tunables could fix any issues I have
come across but believe me I have spent 100s of man hours on issues, and
tuned everything I could find.

To me this 32767 limit on somaxconn seems restrive and I vote for it been
bumped to at least 8x that amount as a minimum.  A more suitable default
would probably be around 1024 as well instead of 128.  Dead lingering
connections in timewait etc. all use one of these, and that can very easily
get into the 1000s.

Chris