Pause Mark Start took a long time

Erik Osterlund erik.osterlund at oracle.com
Wed Jul 13 08:03:56 UTC 2022


Hi,

The GC code does almost nothing in the mark start operation, so I have a difficult time seeing that the actual GC code would have much to do with this kind of delay. However, it does do some logging. I wonder if the log statement in the safepoint is being flushed to disk synchronously, and since you are running in some kind of cloud environment, perhaps the disk is accessed over the network, which might experience some kind of delays. If that is the case, then perhaps using -Xlog:async instead might be a good idea for you. It should be available in JDK 17 which you appear to be using.

Please let me know if that helps or not.

Thanks,
/Erik

On 13 Jul 2022, at 09:44, kang wangk <wangkang0902 at gmail.com<mailto:wangkang0902 at gmail.com>> wrote:


Hi,

  I am running ZGC in production(Deployed in k8s) with following settings

-Xms4000m -Xmx4000m -XX:ConcGCThreads=2 -XX:-UseDynamicNumberOfGCThreads -XX:+UseZGC -XX:-ZProactive -XX:ZAllocationSpikeTolerance=3 -XX:ZCollectionInterval=60

Occasionally encounter a long Pause Mark Start time(the longest pause time  is 5s)

Here are some GC logs blow

[2022-07-12T10:52:52.242+0800][10][info][gc,init] Initializing The Z Garbage Collector
[2022-07-12T10:52:52.242+0800][10][info][gc,init] Version: 17.0.3+8-LTS-111 (release)
[2022-07-12T10:52:52.242+0800][10][info][gc,init] NUMA Support: Disabled
[2022-07-12T10:52:52.242+0800][10][info][gc,init] CPUs: 64 total, 4 available
[2022-07-12T10:52:52.242+0800][10][info][gc,init] Memory: 10240M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Large Page Support: Disabled
[2022-07-12T10:52:52.243+0800][10][info][gc,init] GC Workers: 2/3 (static)
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Address Space Type: Contiguous/Unrestricted/Complete
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Address Space Size: 64000M x 3 = 192000M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Heap Backing File: /memfd:java_heap
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Heap Backing Filesystem: tmpfs (0x1021994)
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Min Capacity: 4000M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Initial Capacity: 4000M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Max Capacity: 4000M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Medium Page Size: 32M
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Pre-touch: Enabled
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Available space on backing filesystem: N/A
[2022-07-12T10:52:52.243+0800][10][info][gc,init] Uncommit: Implicitly Disabled (-Xms equals -Xmx)
[2022-07-12T10:52:55.014+0800][10][info][gc,init] Runtime Workers: 3
[2022-07-12T10:52:55.014+0800][10][info][gc     ] Using The Z Garbage Collector

[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ] === Garbage Collection Statistics =======================================================================================================================
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]                                                              Last 10s              Last 10m              Last 10h                Total
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]                                                              Avg / Max             Avg / Max             Avg / Max             Avg / Max
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]   Collector: Garbage Collection Cycle                      0.000 / 0.000       215.897 / 245.004     199.964 / 281.004     198.501 / 327.779     ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]  Contention: Mark Segment Reset Contention                     0 / 0                 0 / 3                 0 / 13                0 / 17          ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]  Contention: Mark SeqNum Reset Contention                      0 / 0                 0 / 2                 0 / 3                 0 / 4           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: Allocation Stall                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: Allocation Stall                              0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: GC Locker Stall                                   0 / 0                 0 / 1                 0 / 1                 0 / 1           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: GC Locker Stall                               0.000 / 0.000         0.001 / 0.001         0.022 / 0.138         0.032 / 0.197       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: Relocation Stall                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Critical: Relocation Stall                              0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Allocation Rate                                 106 / 124             109 / 240             100 / 308             104 / 352         MB/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Out Of Memory                                     0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Page Cache Flush                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           MB/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L1                                53 / 62               54 / 76               49 / 94               51 / 176         ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L2                                 0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L3                                 0 / 0                 0 / 0                 0 / 1                 0 / 123         ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Page Cache Miss                                   0 / 0                 0 / 0                 0 / 0                 0 / 1           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Uncommit                                          0 / 0                 0 / 0                 0 / 0                 0 / 0           MB/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Undo Object Allocation Failed                     0 / 0                 0 / 94                0 / 189               0 / 438         ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Undo Object Allocation Succeeded                  0 / 0                 0 / 90                0 / 571               0 / 571         ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      Memory: Undo Page Allocation                              0 / 1                 0 / 3                 0 / 7                 0 / 9           ops/s
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark                               0.000 / 0.000       162.242 / 191.178     149.779 / 233.888     149.319 / 253.310     ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark Continue                      0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark Free                          0.000 / 0.000         0.001 / 0.003         0.001 / 0.035         0.001 / 0.035       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Process Non-Strong References      0.000 / 0.000        40.077 / 43.167       36.932 / 73.540       35.951 / 73.540      ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Relocate                           0.000 / 0.000         9.764 / 13.321        9.670 / 18.334        9.656 / 64.541      ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Reset Relocation Set               0.000 / 0.000         0.246 / 0.377         0.234 / 0.385         0.228 / 0.459       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Concurrent Select Relocation Set              0.000 / 0.000         2.843 / 3.684         2.670 / 4.496         2.647 / 9.518       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Pause Mark End                                0.000 / 0.000         0.036 / 0.059         0.030 / 0.080         0.029 / 0.105       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Pause Mark Start                              0.000 / 0.000         0.040 / 0.050         0.057 / 17.923        0.085 / 116.781     ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]       Phase: Pause Relocate Start                          0.000 / 0.000         0.022 / 0.032         0.021 / 0.060         0.021 / 0.063       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Classes Purge                      0.000 / 0.000         1.484 / 2.016         1.290 / 2.861         1.230 / 3.239       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Classes Unlink                     0.000 / 0.000        34.848 / 38.008       32.338 / 68.815       31.461 / 68.815      ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark                               0.000 / 0.000       158.162 / 187.147     146.016 / 230.654     145.542 / 250.339     ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark Try Flush                     0.000 / 0.000         0.208 / 0.536         0.197 / 79.168        0.179 / 79.168      ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark Try Terminate                 0.000 / 0.000         0.468 / 1.076         0.455 / 5.019         0.449 / 32.389      ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent References Enqueue                 0.000 / 0.000         0.001 / 0.008         0.002 / 0.015         0.002 / 0.031       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent References Process                 0.000 / 0.000         0.417 / 0.662         0.297 / 0.828         0.305 / 4.058       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots ClassLoaderDataGraph         0.000 / 0.000         0.421 / 1.062         0.393 / 1.062         0.392 / 1.062       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots CodeCache                    0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots JavaThreads                  0.000 / 0.000         2.863 / 3.649         2.609 / 4.023         2.636 / 4.221       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots OopStorageSet                0.000 / 0.000         0.101 / 0.148         0.094 / 0.172         0.092 / 0.748       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Weak Roots OopStorageSet           0.000 / 0.000         2.895 / 3.442         2.633 / 3.805         2.588 / 4.245       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]    Subphase: Pause Mark Try Complete                       0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.003 / 0.006       ms
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ]      System: Java Threads                                      0 / 0               204 / 227             173 / 227             167 / 227         threads
[2022-07-13T14:18:33.036+0800][18][info][gc,stats    ] =========================================================================================================================================================
[2022-07-13T14:18:37.836+0800][16][info][gc,task     ] GC(2822) Using 2 workers
[2022-07-13T14:18:38.568+0800][23][info][gc,phases   ] GC(2822) Pause Mark Start 731.329ms
[2022-07-13T14:18:38.568+0800][23][info][safepoint   ] Safepoint "ZMarkStart", Time since last: 33682417078 ns, Reaching safepoint: 78660 ns, At safepoint: 731509582 ns, Total: 731588242 ns
[2022-07-13T14:18:38.763+0800][16][info][gc,phases   ] GC(2822) Concurrent Mark 195.357ms
[2022-07-13T14:18:38.763+0800][23][info][gc,phases   ] GC(2822) Pause Mark End 0.037ms
[2022-07-13T14:18:38.763+0800][23][info][safepoint   ] Safepoint "ZMarkEnd", Time since last: 195457277 ns, Reaching safepoint: 59774 ns, At safepoint: 69617 ns, Total: 129391 ns
[2022-07-13T14:18:38.763+0800][16][info][gc,phases   ] GC(2822) Concurrent Mark Free 0.002ms
[2022-07-13T14:18:38.807+0800][16][info][gc,phases   ] GC(2822) Concurrent Process Non-Strong References 43.503ms
[2022-07-13T14:18:38.807+0800][16][info][gc,phases   ] GC(2822) Concurrent Reset Relocation Set 0.266ms
[2022-07-13T14:18:38.811+0800][16][info][gc,phases   ] GC(2822) Concurrent Select Relocation Set 3.787ms
[2022-07-13T14:18:38.811+0800][23][info][gc,phases   ] GC(2822) Pause Relocate Start 0.022ms
[2022-07-13T14:18:38.811+0800][23][info][safepoint   ] Safepoint "ZRelocateStart", Time since last: 47720139 ns, Reaching safepoint: 71865 ns, At safepoint: 50103 ns, Total: 121968 ns
[2022-07-13T14:18:38.823+0800][16][info][gc,phases   ] GC(2822) Concurrent Relocate 12.090ms
[2022-07-13T14:18:38.823+0800][16][info][gc,load     ] GC(2822) Load: 17.47/17.79/16.25
[2022-07-13T14:18:38.823+0800][16][info][gc,mmu      ] GC(2822) MMU: 2ms/0.0%, 5ms/0.0%, 10ms/0.0%, 20ms/0.0%, 50ms/0.0%, 100ms/0.0%
[2022-07-13T14:18:38.823+0800][16][info][gc,marking  ] GC(2822) Mark: 2 stripe(s), 2 proactive flush(es), 1 terminate flush(es), 0 completion(s), 0 continuation(s)
[2022-07-13T14:18:38.823+0800][16][info][gc,marking  ] GC(2822) Mark Stack Usage: 32M
[2022-07-13T14:18:38.823+0800][16][info][gc,nmethod  ] GC(2822) NMethods: 23051 registered, 1360 unregistered
[2022-07-13T14:18:38.823+0800][16][info][gc,metaspace] GC(2822) Metaspace: 113M used, 114M committed, 516M reserved
[2022-07-13T14:18:38.823+0800][16][info][gc,ref      ] GC(2822) Soft: 1059 encountered, 271 discovered, 0 enqueued
[2022-07-13T14:18:38.823+0800][16][info][gc,ref      ] GC(2822) Weak: 16086 encountered, 1352 discovered, 0 enqueued
[2022-07-13T14:18:38.823+0800][16][info][gc,ref      ] GC(2822) Final: 30 encountered, 2 discovered, 0 enqueued
[2022-07-13T14:18:38.823+0800][16][info][gc,ref      ] GC(2822) Phantom: 290 encountered, 250 discovered, 1 enqueued
[2022-07-13T14:18:38.823+0800][16][info][gc,reloc    ] GC(2822) Small Pages: 1852 / 3704M, Empty: 698M, Relocated: 10M, In-Place: 0
[2022-07-13T14:18:38.823+0800][16][info][gc,reloc    ] GC(2822) Medium Pages: 2 / 64M, Empty: 32M, Relocated: 0M, In-Place: 0
[2022-07-13T14:18:38.823+0800][16][info][gc,reloc    ] GC(2822) Large Pages: 0 / 0M, Empty: 0M, Relocated: 0M, In-Place: 0
[2022-07-13T14:18:38.823+0800][16][info][gc,reloc    ] GC(2822) Forwarding Usage: 3M
[2022-07-13T14:18:38.823+0800][16][info][gc          ] GC(2822) Garbage Collection (High Usage) 3768M(94%)->238M(6%)
[2022-07-13T14:18:42.813+0800][23][info][safepoint   ] Safepoint "Cleanup", Time since last: 4000282554 ns, Reaching safepoint: 1161862 ns, At safepoint: 32230 ns, Total: 1194092 ns
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ] === Garbage Collection Statistics =======================================================================================================================
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]                                                              Last 10s              Last 10m              Last 10h                Total
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]                                                              Avg / Max             Avg / Max             Avg / Max             Avg / Max
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]   Collector: Garbage Collection Cycle                    987.238 / 987.238     256.494 / 987.238     200.744 / 987.238     198.781 / 987.238     ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]  Contention: Mark Segment Reset Contention                     0 / 0                 0 / 3                 0 / 13                0 / 17          ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]  Contention: Mark SeqNum Reset Contention                      0 / 0                 0 / 2                 0 / 3                 0 / 4           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: Allocation Stall                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: Allocation Stall                              0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: GC Locker Stall                                   0 / 0                 0 / 1                 0 / 1                 0 / 1           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: GC Locker Stall                               0.000 / 0.000         0.001 / 0.001         0.022 / 0.138         0.032 / 0.197       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: Relocation Stall                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Critical: Relocation Stall                              0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Allocation Rate                                 105 / 128             109 / 240             100 / 308             104 / 352         MB/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Out Of Memory                                     0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Page Cache Flush                                  0 / 0                 0 / 0                 0 / 0                 0 / 0           MB/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L1                                51 / 64               54 / 76               49 / 94               51 / 176         ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L2                                 0 / 0                 0 / 0                 0 / 0                 0 / 0           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Page Cache Hit L3                                 1 / 16                0 / 16                0 / 16                0 / 123         ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Page Cache Miss                                   0 / 0                 0 / 0                 0 / 0                 0 / 1           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Uncommit                                          0 / 0                 0 / 0                 0 / 0                 0 / 0           MB/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Undo Object Allocation Failed                     1 / 14                0 / 94                0 / 189               0 / 438         ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Undo Object Allocation Succeeded                 10 / 109               0 / 109               0 / 571               0 / 571         ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      Memory: Undo Page Allocation                              0 / 4                 0 / 4                 0 / 7                 0 / 9           ops/s
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark                             195.357 / 195.357     163.985 / 195.357     149.824 / 233.888     149.336 / 253.310     ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark Continue                      0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Mark Free                          0.002 / 0.002         0.001 / 0.003         0.001 / 0.035         0.001 / 0.035       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Process Non-Strong References     43.503 / 43.503       40.257 / 43.503       36.939 / 73.540       35.954 / 73.540      ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Relocate                          12.090 / 12.090        9.887 / 13.321        9.672 / 18.334        9.657 / 64.541      ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Reset Relocation Set               0.266 / 0.266         0.247 / 0.377         0.234 / 0.385         0.228 / 0.459       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Concurrent Select Relocation Set              3.787 / 3.787         2.893 / 3.787         2.671 / 4.496         2.647 / 9.518       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Pause Mark End                                0.037 / 0.037         0.036 / 0.059         0.030 / 0.080         0.029 / 0.105       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Pause Mark Start                            731.329 / 731.329      38.529 / 731.329       0.782 / 731.329       0.344 / 731.329     ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]       Phase: Pause Relocate Start                          0.022 / 0.022         0.022 / 0.032         0.021 / 0.060         0.021 / 0.063       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Classes Purge                      1.826 / 1.826         1.502 / 2.016         1.290 / 2.861         1.230 / 3.239       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Classes Unlink                    38.001 / 38.001       35.014 / 38.008       32.344 / 68.815       31.464 / 68.815      ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark                             190.810 / 191.151     159.881 / 191.151     146.060 / 230.654     145.558 / 250.339     ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark Try Flush                     0.259 / 0.548         0.211 / 0.548         0.197 / 79.168        0.179 / 79.168      ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Mark Try Terminate                 0.545 / 1.065         0.472 / 1.076         0.456 / 5.019         0.449 / 32.389      ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent References Enqueue                 0.009 / 0.009         0.002 / 0.009         0.002 / 0.015         0.002 / 0.031       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent References Process                 0.338 / 0.338         0.412 / 0.662         0.297 / 0.828         0.305 / 4.058       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots ClassLoaderDataGraph         0.376 / 0.659         0.419 / 1.062         0.393 / 1.062         0.392 / 1.062       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots CodeCache                    0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.000 / 0.000       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots JavaThreads                  3.345 / 3.622         2.889 / 3.649         2.610 / 4.023         2.636 / 4.221       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Roots OopStorageSet                0.103 / 0.110         0.101 / 0.148         0.094 / 0.172         0.092 / 0.748       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Concurrent Weak Roots OopStorageSet           2.779 / 2.780         2.889 / 3.442         2.633 / 3.805         2.588 / 4.245       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]    Subphase: Pause Mark Try Complete                       0.000 / 0.000         0.000 / 0.000         0.000 / 0.000         0.003 / 0.006       ms
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ]      System: Java Threads                                    226 / 234             205 / 234             173 / 234             167 / 234         threads
[2022-07-13T14:18:43.036+0800][18][info][gc,stats    ] =========================================================================================================================================================

In my opinion, this stage is very light. What can cause this phenomenon

Thanks!

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