In the last two years we were suffering from jenkins CPU and memory utilization. The following switches made miracle:
JAVA_ARGS="-Djava.awt.headless=true -Xms1g -Xmx6g -XX:MaxPermSize=1G -XX:+UseParNewGC -Dorg.kohsuke.stapler.compression.CompressionFilter.disabled=true"
We see ~60% CPU usage at peaks(!) on a Xeon E5504 2.00GHz, instead of constant 400%.
Currently there are 80 executors.