we use jenkins Jenkins ver. 1.558
on a RHEL 6.4 platform (x86_64)
2 vcpu & 6 Go RAM
jdk 1.7.0_51 x64

JAVA OPTIONS: -Xmx1g -Xms1g -XX:MaxPermSize=256m

we have 150 jobs and 20 slaves.
all the slave are taken online on demand (and offline when not used).

each time a build is launched, the memory (of the master) used grow (and is not released).
after many hours, the machine swap.

the heap space and permegen space are correctly used.
The native memory used never stop to increase