是否存在一些介绍 gc 日志的官方文件?

Question

今天有一个索引慢日志，

[2020-02-12T15:52:37,418][WARN ][i.i.s.index              ] [node-1] [company/KTngnM6ASD-_KdU0FFAWRA] took[22.7s], took_millis[22703], type[_doc], id[20080943028], routing[], source[{...}]

然后检查gc.log找出原因，

[2020-02-12T07:52:37.417+0000][22539][safepoint      ] Total time for which application threads were stopped: 0.0004935 seconds, Stopping threads took: 0.0001389 seconds
[2020-02-12T07:52:37.586+0000][22539][safepoint      ] Application time: 0.1682439 seconds
[2020-02-12T07:52:37.586+0000][22539][safepoint      ] Entering safepoint region: GenCollectForAllocation
[2020-02-12T07:52:37.586+0000][22539][gc,start       ] GC(315124) Pause Young (Allocation Failure)
[2020-02-12T07:52:37.586+0000][22539][gc,task        ] GC(315124) Using 8 workers of 8 for evacuation
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) Desired survivor size 34865152 bytes, new threshold 3 (max threshold 6)
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) Age table with threshold 3 (max threshold 6)
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) - age   1:   22998672 bytes,   22998672 total
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) - age   2:    4966112 bytes,   27964784 total
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) - age   3:   10219520 bytes,   38184304 total
[2020-02-12T07:52:37.641+0000][22539][gc,age         ] GC(315124) - age   4:    4875304 bytes,   43059608 total
[2020-02-12T07:52:37.641+0000][22539][gc,heap        ] GC(315124) ParNew: 597611K->52614K(613440K)
[2020-02-12T07:52:37.641+0000][22539][gc,heap        ] GC(315124) CMS: 4992477K->4998973K(16095680K)
[2020-02-12T07:52:37.641+0000][22539][gc,metaspace   ] GC(315124) Metaspace: 103488K->103488K(1144832K)
[2020-02-12T07:52:37.641+0000][22539][gc             ] GC(315124) Pause Young (Allocation Failure) 5459M->4933M(16317M) 54.724ms
[2020-02-12T07:52:37.641+0000][22539][gc,cpu         ] GC(315124) User=0.35s Sys=0.00s Real=0.06s
[2020-02-12T07:52:37.641+0000][22539][safepoint      ] Leaving safepoint region

似乎GC还可以，但是有些日志无法理解，例如

Entering safepoint region: Cleanup
Entering safepoint region: RevokeBias
Entering safepoint region: GenCollectForAllocation

Cleanup、RevokeBias、GenCollectForAllocation是什么意思？Application time是什么意思？为什么如此不同？

Application time: 0.1382641 seconds
Application time: 13.2106552 seconds
Application time: 106.3031188 seconds 

Answer 1

有趣的是，你提到了一些事情，但没有为它们提供日志。无论如何：

RevokeBias是当发生撤销偏置锁定或偏置锁定的"胖"锁放气时。

GenCollectForAllocation- 这就是触发安全点的原因。您可以将其读作："分配失败的代际收集器"。仅供参考，还有许多其他原因。

Cleanup是任何安全点清理任务。

AFAIK，如果需要更多详细信息，则需要启用跟踪日志级别。