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Jstat specific parameter values: YGCT FGCT GCT

I need to use jstat to measure some parameters of a GC program. Jstat provides a set of parameters (S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT GCT) Of these, I'm a little confused about the descriptions of YGCT, FGCT and GCT.

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

I have 2 questions.

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

2) How can I find out the unit of time that they mention? (milliseconds / seconds / ....)

I referenced many documents, including

Interpretation of 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 this does not answer my real question.
Can anyone, as happened with jstat, help me with this?

Thanks.

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2 answers
  • YGCT - Seconds Spent in Young Generation Collections with JVM Start
  • FGCT - Seconds spent on complete garbage collection since the JVM is running
  • GCT - the sum of these two values
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S0C – Current survivor space 0 capacity (KB). S1C – Current survivor space 1 capacity (KB). S0U – Survivor space 0 utilization (KB). S1U – Survivor space 1 utilization (KB). EC – Current eden space capacity (KB). EU – Eden space utilization (KB). OC – Current old space capacity (KB). OU – Old space utilization (KB). PC – Current permanent space capacity (KB). PU – Permanent space utilization (KB). YGC – Number of young generation GC Events. YGCT – Young generation garbage collection time. FGC – Number of full GC events. FGCT – Full garbage collection time. GCT – Total garbage collection time. FGCT +YGCT = GCT FGCT /FGC = avg time taken per full gc cycle YGCT / YGC = avg time taken per each young GC

they are useful when you are dealing with GC statistics.

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