STW的GC日志，发现FinalReference 有1118615个引用，这个是有什么原因累计这么多的，现象：大概两天会发生一次0.5秒的stw。
2020-07-09T12:26:31.422+0800: 573951.870: [GC (CMS Initial Mark) [1 CMS-initial-mark: 2865303K(4608000K)] 3116234K(7372800K), 0.0168038 secs] [Times: user=0.12 sys=0.00, real=0.02 secs]
2020-07-09T12:26:31.441+0800: 573951.888: [CMS-concurrent-mark-start]
2020-07-09T12:26:32.046+0800: 573952.493: [CMS-concurrent-mark: 0.549/0.605 secs] [Times: user=1.22 sys=0.01, real=0.60 secs]
2020-07-09T12:26:32.047+0800: 573952.494: [CMS-concurrent-preclean-start]
2020-07-09T12:26:32.047+0800: 573952.494:[Preclean SoftReferences, 0.0000424 secs]
2020-07-09T12:26:32.047+0800: 573952.494:[Preclean WeakReferences, 0.0006816 secs]
2020-07-09T12:26:32.048+0800: 573952.495:[Preclean FinalReferences, 0.0683659 secs]
2020-07-09T12:26:32.116+0800: 573952.563:[Preclean PhantomReferences, 0.0001505 secs]
2020-07-09T12:26:32.127+0800: 573952.574: [CMS-concurrent-preclean: 0.080/0.080 secs] [Times: user=0.08 sys=0.00, real=0.08 secs]
2020-07-09T12:26:32.128+0800: 573952.575: [CMS-concurrent-abortable-preclean-start]
CMS: abort preclean due to time 2020-07-09T12:26:37.288+0800: 573957.735: [CMS-concurrent-abortable-preclean: 4.459/5.160 secs] [Times: user=4.61 sys=0.00, real=5.16 secs]
2020-07-09T12:26:37.298+0800: 573957.745: [GC (CMS Final Remark)
[YG occupancy: 294427 K (2764800 K)]2020-07-09T12:26:37.298+0800: 573957.746:
[Rescan (parallel) , 0.0181012 secs]2020-07-09T12:26:37.316+0800: 573957.764:
[weak refs processing2020-07-09T12:26:37.317+0800: 573957.764:
[SoftReference, 21 refs, 0.0008097 secs]2020-07-09T12:26:37.317+0800: 573957.765:
[WeakReference, 0 refs, 0.0004331 secs]2020-07-09T12:26:37.318+0800: 573957.765:
[FinalReference, 1118615 refs, 0.5211252 secs]2020-07-09T12:26:37.839+0800: 573958.286:
[PhantomReference, 0 refs, 0 refs, 0.0011382 secs]2020-07-09T12:26:37.840+0800: 573958.287:
[JNI Weak Reference, 0.0000579 secs], 0.5236547 secs]2020-07-09T12:26:37.840+0800: 573958.288:
[class unloading, 0.0410670 secs]2020-07-09T12:26:37.881+0800: 573958.329:
[scrub symbol table, 0.0152763 secs]2020-07-09T12:26:37.897+0800: 573958.344:
[scrub string table, 0.0018916 secs]
[1 CMS-remark: 2865303K(4608000K)] 3159730K(7372800K), 0.6180956 secs] [Times: user=3.94 sys=0.00, real=0.62 secs]
2020-07-09T12:26:37.918+0800: 573958.365: [CMS-concurrent-sweep-start]
2020-07-09T12:26:39.216+0800: 573959.663: [CMS-concurrent-sweep: 1.298/1.298 secs] [Times: user=2.50 sys=0.00, real=1.30 secs]
2020-07-09T12:26:39.217+0800: 573959.664: [CMS-concurrent-reset-start]
2020-07-09T12:26:39.224+0800: 573959.671: [CMS-concurrent-reset: 0.008/0.008 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]
