connection rate in ircd? ( 2.10.3p3 )

[Timothee Besset <ttimo@xxxxxxxxx>]

I've been doing a few basic stress testing operations on ircd on a Linux
system, and I'm finding that the rate at which TCP connections to the ircd
port are accepted is limited, and fairly low. My tests show around 5
connections/second. If I try to connect at once around 250 clients, all
TCP connections get opened, but about 60 of them get closed by ircd a few
seconds after that (the others get in fine).

To perform those tests, I disabled both the SLOW_ACCEPT and CLONE_CHECK,
so that I can connect a lot of clients from localhost (to mimic what
happens on an internet server when many clients are reconnecting). Opening
more ports allows for a higher global rate when the connections are evenly
distributed (more or less linear); but my real problem is to understand
why is the connection rate so low to being with, and mostly wether it's an
OS thing or wether it's something ircd has control over (in case I would
have missed it in the source)?

TTimo