"-Xlog:gc=trace" - Lowest GC Logging Level: TRACE

Java GC Tutorials - Herong's Tutorial Examples

∟"-Xlog:gc=trace" - Lowest GC Logging Level: TRACE

This section describes the garbage collection logging option, '-Xlog:gc=trace', which prints out log messages from the GC channel at the TRACE level, which is lowest logging level.

In the second test, let's try the "-Xlog:gc=trace" garbage collection logging option to get more logging messages to the lowest level of TRACE in the log file:

herong> java -Xms2m -Xmx64m -Xlog:gc=trace:gc.log GarbageCollection

Step/TotalMemory/FreeMemory/UsedMemory:
1   2031616   698848   1332768
2   3874816   1473392   2401424
3   3874816   425688   3449128
4   8970240   4442016   4528224
...
(Ctrl-C)

herong> more gc.log
[0.005s][trace][gc] MarkStackSize: 4096k  MarkStackSizeMax: 16384k
[0.013s][debug][gc] ConcGCThreads: 2 offset 16
[0.013s][debug][gc] ParallelGCThreads: 8
[0.013s][debug][gc] Initialize mark stack with 4096 chunks, maximum 16384
[0.014s][info ][gc] Using G1
[0.032s][info ][gc] Periodic GC disabled
...
[0.584s][info ][gc] GC(34) Pause Young (Normal) (G1 Evacuation Pause) ...
[0.587s][info ][gc] GC(35) Pause Young (Normal) (G1 Evacuation Pause) ...
[0.590s][trace][gc] GC(36) Restored 3175 marks                        ...
[0.590s][info ][gc] GC(36) To-space exhausted                         ...
[0.590s][info ][gc] GC(36) Pause Young (Normal) (G1 Evacuation Pause) ...
[0.590s][info ][gc] GC(27) Pause Cleanup 63M->63M(64M) 0.065ms        ...
[0.593s][trace][gc] GC(37) Restored 10478 marks                       ...
[0.593s][info ][gc] GC(37) To-space exhausted                         ...
[0.593s][info ][gc] GC(37) Pause Young (Prepare Mixed) (G1 Evacuation ...
[0.594s][debug][gc] GC(38) Clear Next Bitmap 0.261ms                  ...
[0.610s][trace][gc] GC(38) Restored 11390 marks                       ...
[0.611s][info ][gc] GC(38) Pause Full (G1 Evacuation Pause) 63M->34M(6...
[0.611s][info ][gc] GC(27) Concurrent Cycle 56.572ms
...