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javagarbage-collection

GC pause duration from GC logs

We are using UseParallelGC.

GC logs looks like

2016-06-09T19:38:17.362+0000: 655312.397: [Full GC (Ergonomics) [PSYoungGen: 229127K->0K(3882496K)] [ParOldGen: 8350636K->5628357K(8388608K)] 8579764K->5628357K(12271104K), [Metaspace: 111462K->111462K(1150976K)], 39.9246114 secs] [Times: user=689.16 sys=0.00, real=39.92 secs]

We want to know what is GC pause time. Is it 689.16 sec or 39.9246114 secs?

Solution

  • User means the time spent in CPU in user mode. If you have several cores you can use several seconds of user time per second (every core counts).

    Real time means wall clock time, which probably is the time you are most interested in.

    So your JVM was paused for 39.92 seconds, using a total of 689 seconds of CPU time (which means you have more than 17 cores).