2021-12-11T10:44:32.308+0800: 757446.130: [GC pause (G1 Evacuation Pause) (young), 0.4317106 secs]
   [Parallel Time: 426.8 ms, GC Workers: 8]
      [GC Worker Start (ms): Min: 757446130.4, Avg: 757446130.5, Max: 757446130.6, Diff: 0.1]
      [Ext Root Scanning (ms): Min: 403.2, Avg: 405.7, Max: 406.9, Diff: 3.7, Sum: 3245.7]
      [Update RS (ms): Min: 0.4, Avg: 0.9, Max: 1.5, Diff: 1.1, Sum: 7.2]
         [Processed Buffers: Min: 16, Avg: 25.0, Max: 36, Diff: 20, Sum: 200]
      [Scan RS (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.1]
      [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
      [Object Copy (ms): Min: 18.5, Avg: 19.9, Max: 22.1, Diff: 3.6, Sum: 159.2]
      [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
         [Termination Attempts: Min: 1, Avg: 1.2, Max: 2, Diff: 1, Sum: 10]
      [GC Worker Other (ms): Min: 0.0, Avg: 0.0, Max: 0.1, Diff: 0.1, Sum: 0.3]
      [GC Worker Total (ms): Min: 426.5, Avg: 426.6, Max: 426.6, Diff: 0.1, Sum: 3412.5]
      [GC Worker End (ms): Min: 757446557.0, Avg: 757446557.1, Max: 757446557.1, Diff: 0.1]
   [Code Root Fixup: 0.0 ms]
   [Code Root Purge: 0.0 ms]
   [Clear CT: 0.2 ms]
   [Other: 4.6 ms]
      [Choose CSet: 0.0 ms]
      [Ref Proc: 3.3 ms]
      [Ref Enq: 0.3 ms]
      [Redirty Cards: 0.2 ms]
      [Humongous Register: 0.0 ms]
      [Humongous Reclaim: 0.0 ms]
      [Free CSet: 0.1 ms]
   [Eden: 400.0M(400.0M)->0.0B(404.0M) Survivors: 8192.0K->4096.0K Heap: 4041.4M(8192.0M)->3638.9M(8192.0M)]

Ext Root Scanning慢一般啥原因，怎么优化。