Hi All
We are experimenting G1 GC for one of our application. Please find our
application settings GC Settings
-XX:MaxPermSize=512m
-XX:+UseG1GC
-XX:G1ReservePercent=40
-XX:ConcGCThreads=14
-XX:+PrintGCDateStamps
-XX:+PrintTenuringDistribution
-XX:+PrintGCApplicationConcurrentTime
-XX:+PrintGCApplicationStoppedTime
JVM : JVM : jdk_7u40_x64
While scanning for instances which caused application threads to get stopped ,
we found the following instance in our GC logs.
GC Logs
=======
{Heap before GC invocations=57832 (full 1):
garbage-first heap total 5242880K, used 3111240K [0x00000006a0000000,
0x00000007e0000000, 0x00000007e0000000)
region size 2048K, 672 young (1376256K), 1 survivors (2048K)
compacting perm gen total 98304K, used 96772K [0x00000007e0000000,
0x00000007e6000000, 0x0000000800000000)
the space 98304K, 98% used [0x00000007e0000000, 0x00000007e5e81338,
0x00000007e5e81400, 0x00000007e6000000)
No shared spaces configured.
2016-10-05T12:13:19.835-0400: 80080.725: [GC pause (young)
Desired survivor size 88080384 bytes, new threshold 15 (max 15)
- age 1: 136824 bytes, 136824 total
- age 2: 11120 bytes, 147944 total
- age 3: 11408 bytes, 159352 total
- age 4: 9248 bytes, 168600 total
- age 5: 8632 bytes, 177232 total
- age 6: 8224 bytes, 185456 total
- age 7: 8784 bytes, 194240 total
- age 8: 87856 bytes, 282096 total
- age 9: 25080 bytes, 307176 total
- age 10: 8272 bytes, 315448 total
- age 11: 7984 bytes, 323432 total
- age 12: 14120 bytes, 337552 total
- age 13: 9824 bytes, 347376 total
- age 14: 11616 bytes, 358992 total
- age 15: 8032 bytes, 367024 total
, 51.2453720 secs]
[Parallel Time: 11.3 ms, GC Workers: 16]
[GC Worker Start (ms): Min: 80080725.7, Avg: 80080725.8, Max: 80080725.9,
Diff: 0.2]
[Ext Root Scanning (ms): Min: 4.4, Avg: 5.2, Max: 10.7, Diff: 6.3, Sum:
83.5]
[Update RS (ms): Min: 0.0, Avg: 0.8, Max: 1.3, Diff: 1.3, Sum: 13.4]
[Processed Buffers: Min: 0, Avg: 3.0, Max: 7, Diff: 7, Sum: 48]
[Scan RS (ms): Min: 0.1, Avg: 0.2, Max: 0.3, Diff: 0.2, Sum: 3.7]
[Object Copy (ms): Min: 0.1, Avg: 0.4, Max: 0.6, Diff: 0.5, Sum: 6.0]
[Termination (ms): Min: 0.0, Avg: 4.3, Max: 4.6, Diff: 4.6, Sum: 68.6]
[GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.1, Sum: 1.0]
[GC Worker Total (ms): Min: 10.9, Avg: 11.0, Max: 11.2, Diff: 0.3, Sum:
176.3]
[GC Worker End (ms): Min: 80080736.7, Avg: 80080736.8, Max: 80080736.8,
Diff: 0.1]
[Code Root Fixup: 0.0 ms]
[Clear CT: 0.4 ms]
[Other: 51233.7 ms]
[Choose CSet: 0.0 ms]
[Ref Proc: 17.2 ms]
[Ref Enq: 50800.9 ms]
[Free CSet: 381.2 ms]
[Eden: 1342.0M(1342.0M)->0.0B(254.0M) Survivors: 2048.0K->2048.0K Heap:
3038.3M(5120.0M)->1696.2M(5120.0M)]
Heap after GC invocations=57833 (full 1):
garbage-first heap total 5242880K, used 1736897K [0x00000006a0000000,
0x00000007e0000000, 0x00000007e0000000)
region size 2048K, 1 young (2048K), 1 survivors (2048K)
compacting perm gen total 98304K, used 96772K [0x00000007e0000000,
0x00000007e6000000, 0x0000000800000000)
the space 98304K, 98% used [0x00000007e0000000, 0x00000007e5e81338,
0x00000007e5e81400, 0x00000007e6000000)
No shared spaces configured.
}
[Times: user=0.00 sys=17.51, real=51.28 secs]
2016-10-05T12:14:11.208-0400: 80132.098: Total time for which application
threads were stopped: 51.3791600 seconds
It looks like Reference Enqueue ( Ref Enq) event took nearly 50 seconds to
complete. Could you please help me in understanding , why it might take so
much time to complete. Do I need to add any diagnostic flag to get more
information ?. Apologies , If similar question was answered before in the
mailing list. Any help is really appreciated.
Thanks and Regards
Prasanna
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