Specific meanings of jstat parameters : YGCT FGCT GCT

garbage-collection jstat
user1182584 picture user1182584 · Apr 22, 2015 · Viewed 7k times · Source

I need to use jstat to measure some GC parameters of a program. Jstat provides set of parameters ( S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT) From those I am bit confused with the descriptions for YGCT, FGCT and GCT.

(YGCT Young generation garbage collection time.
FGCT Full garbage collection time.
GCT Total garbage collection time.)

I have 2 questions.

1) What does these three parameters (YGCT, FGCT and GCT) actually measure? A small comparison would be very helpful

2) I how can I know the unit of time that they are mentioning? (milliseconds/ seconds/.... )

I referred many documentations including

Interpreting jstat results
http://www.cubrid.org/blog/dev-platform/how-to-monitor-java-garbage-collection/
http://docs.oracle.com/javase/6/docs/technotes/tools/share/jstat.html#output_options
But these does not answer my real question.
Could anyone how has experienced with jstat help me with this?

Thank you.

Answer

K Erlandsson picture K Erlandsson · Apr 23, 2015
  • YGCT - Seconds spent in young generation collections since the JVM started
  • FGCT - Seconds spent doing full garbage collections since the JVM started
  • GCT - the sum of the above two values

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