how to optimize performance for openfire 4.0.1

Hi,

Is there any idea to  optimize performance for openfire 4.0.1?

I've got 800+ users, and 50+ groups shared for all users in the Roster.

Every morning when 300+ offline users log on, some user cannot log on before they tried several times.

I'v changed ulimit -n to 65535 on the Openfire server,

and add “ -Djava.nio.channels.spi.SelectorProvider=sun.nio.ch.EPollSelectorProvider” to OPENFIRE_OPTS in /etc/init.d/openfire.

also changed sysctl: net.ipv4.ip_local_port_range = 1024 65000

It seems useless.

This is some info:

Openfire:4.0.1

OS: RHEL6 x86_64

Java:1.8.0_45 Oracle Corporation -- Java HotSpot(TM) 64-Bit Server VM

Java Memory: 1127.00 MB of 54613.50 MB (2.1%) used

Thanks a lot!