you can set them like this, but this usually makes no sense.
You can assume that Wildfire needs about 32 MB for 100 clients (I did not test this, so maybe I’'m completely wrong).
I would set Xms to NrClients/100*32+30%, for 200 connections to 96 MB. Wildfire should never expand its heap, to monitor this you want to specify “-verbose:gc” along with “-Xms96m”.
The Xmx value will likely not be reached, so you could set it to 96 MB, but setting it to 2*Xms seems to be a good choice.
Use SUN’'s jvmstat and VisualGC to tune these values or add the options below to your java call and inspect the gc.log.
PS: Java Garbage Collection Log Options:
-verbose:gc -XX:*PrintGCDetails -XX:*PrintGCTimeStamps -Xloggc:"$/logs/gc.log"