JFR:用事件流观察 JVM 的运行状态

  [0.189s][info][jfr,startup] Started recording 1. No limit specified, using maxsize=250MB as default. | [0.189s][info][jfr,startup] | [0.189s][info][jfr,startup] Use jcmd 64663 JFR.dump name=1 to copy recording data to file. | app done
  记录文件 rec.jfr 大小 575 KB

  Version: 2.1
  Chunks: 1
  Start: 2026-10-03 08:40:11 (UTC)
  Duration: 3 s
  jdk.GCPhaseParallel 6806 172577
  jdk.PromoteObjectInNewPLAB 955 16079
  jdk.NativeLibrary 946 78946
  jdk.ObjectAllocationSample 900 12699
  jdk.SystemProcess 805 82171
  jdk.ModuleExport 505 4912
  jdk.BooleanFlag 490 14424
  jdk.ActiveSetting 360 10031
  jdk.TenuringDistribution 330 3364
  jdk.JavaMonitorEnter 240 5272
  jdk.LongFlag 162 5092
  jdk.ModuleRequire 153 1377
  共 185 种事件产生了记录

  [jdk.GarbageCollection] 共 22 条;前 3 条的关键字段:
    jdk.GarbageCollection {
     startTime = 16:40:11.122 (2026-10-03)
     duration = 1.22 ms
     gcId = 1
     name = "G1New"
     cause = "G1 Evacuation Pause"
     sumOfPauses = 1.22 ms
     longestPause = 1.22 ms
     eventThread = "VM Thread" (osThreadId = 18691)
    }
  [jdk.JavaMonitorEnter] 共 240 条;前 2 条的关键字段:
    jdk.JavaMonitorEnter {
     startTime = 16:40:11.067 (2026-10-03)
     duration = 49.8 ms
     monitorClass = java.lang.Object (classLoader = bootstrap)
     previousOwner = "holder" (javaThreadId = 33)
     address = 0x75E8CF2E60
     eventThread = "worker-3" (javaThreadId = 32)
     stackTrace = [
     App.lambda$main$0(long) line: 5
     java.lang.Thread.run() line: 1583
     ]
    }
  [jdk.ExecutionSample] 共 0 条;前 0 条的关键字段:

  jdk.ExecutionSample:default = {'enabled': 'true', 'period': '20 ms'};profile = {'enabled': 'true', 'period': '10 ms'}
  jdk.JavaMonitorEnter:default = {'enabled': 'true', 'stackTrace': 'true', 'threshold': '20 ms'};profile = {'enabled': 'true', 'stackTrace': 'true', 'threshold': '10 ms'}