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I have enabled GC logging for one of my application. Here is a part of the log. I have searched around to learn how to read this but it appears a bit different to old articles written ofr java 7 or older. I am specifically interested in the value in marked withh **. Why the value is close but diffferent in each line GC parameters as printed in log

Java HotSpot(TM) 64-Bit Server VM (25.5-b02) for linux-amd64 JRE (1.8.0_05-b13), built on Mar 18 2014 00:29:27 by "java_re" with gcc 4.3.0 20080428 (Red Hat 4.3.0-8)
Memory: 4k page, physical 8061636k(1507688k free), swap 8355832k(5938840k free)
CommandLine flags: -XX:InitialHeapSize=268435456 -XX:+ManagementServer -XX:MaxHeapSize=268435456 -XX:+PrintGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC



85.003: [GC (Allocation Failure) [PSYoungGen: 74018K->350K(81408K)] 236281K->162693K(**256512K**), 0.0158446 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
85.200: [GC (Allocation Failure) [PSYoungGen: 75598K->406K(80896K)] 237941K->162843K(**256000K**), 0.0177163 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
85.405: [GC (Allocation Failure) [PSYoungGen: 75654K->390K(81920K)] 238092K->162915K(**257024K**), 0.0237740 secs] [Times: user=0.04 sys=0.00, real=0.03 secs]
86.921: [GC (Allocation Failure) [PSYoungGen: 77173K->2579K(81920K)] 239698K->165199K(**257024K**), 0.0315362 secs] [Times: user=0.06 sys=0.00, real=0.03 secs]
87.225: [GC (Allocation Failure) [PSYoungGen: 79373K->512K(81920K)] 241993K->163869K(**257024K**), 0.0306456 secs] [Times: user=0.05 sys=0.01, real=0.03 secs]
87.551: [GC (Metadata GC Threshold) [PSYoungGen: 42769K->594K(81920K)] 206126K->164086K(257024K), 0.0229454 secs] [Times: user=0.04 sys=0.00, real=0.02 secs]
87.574: [Full GC (Metadata GC Threshold) [PSYoungGen: 594K->0K(81920K)] [ParOldGen: 163492K->47257K(**175104K**)] 164086K->47257K(**257024K**), [Metaspace: 53346K->53346K(1099776K)], 0.9669507 secs] [Times: user=1.77 sys=0.01, real=0.97 secs]
89.126: [GC (Allocation Failure) [PSYoungGen: 76792K->1157K(82432K)] 124050K->48423K(257536K), 0.0158828 secs] [Times: user=0.03 sys=0.00, real=0.02 secs]
İsmail Y.
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Murali
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  • possible duplicate of http://stackoverflow.com/questions/16794783/how-to-read-a-verbosegc-output – BevynQ Oct 01 '14 at 23:55
  • @BevynQ I had visited the link before posting this question. However I failed to understand why max old gen space is varying. Thank you – Murali Oct 02 '14 at 05:41
  • May be you have adaptive sizing policy turned on. Look at details for option `-XX+UseAdaptiveSizePolicy` – Pushkar Jul 28 '15 at 14:38
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    Not a duplicate; the linked answer is specific to Java 7. – Zds Feb 07 '17 at 13:49

1 Answers1

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Rather than viewing the log files directly, tools such as "Garbage Collection and Memory Visualizer (GCMV)" will graph the data and provide statistical analysis.

Chris Bailey
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