Some usages of jstat

-gcutil

$ jstat -gcutil

This command shows utilization percentage of memory spaces of a java process.

S0: Survivor space 0
S1: Survivor space 1
E: Eden space
O: Old-gen space

GC activities

YGC: Young GC count
YGCT: Time spent by Young GC 
FGC: Full GC count
FGCT: Time spent by Full GC


-gc

$ jstat -gc

Find the current vm heap size by sum value under S0C, S01, EC, OC


More at https://docs.oracle.com/javase/8/docs/technotes/tools/unix/jstat.html