使用G1GC时未提供详细信息

Question

我正在将java8u31 （oracle）与以下GC日志记录选项结合使用

 -XX:GCLogFileSize=20971520 -XX:NumberOfGCLogFiles=5 -XX:+PrintGC 
 -XX:+PrintGCApplicationStoppedTime -XX:+PrintGCCause -XX:+PrintGCDateStamps 
 -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:-PrintTenuringDistribution 
 -XX:+UseG1GC -XX:+UseGCLogFileRotation

我的GC日志看起来像

 2015-08-06T09:44:02.486-0400: 1085394.129: Total time for which application threads were stopped: 0.0003136 seconds
 2015-08-06T09:44:02.638-0400: 1085394.281: [GC pause (G1 Evacuation Pause) (young), 0.0354571 secs]
    [Parallel Time: 3.0 ms, GC Workers: 23]
       [GC Worker Start (ms): Min: 1085394281.2, Avg: 1085394281.3, Max: 1085394281.5, Diff: 0.3]
       [Ext Root Scanning (ms): Min: 0.4, Avg: 0.5, Max: 0.9, Diff: 0.6, Sum: 11.4]
       [Update RS (ms): Min: 0.0, Avg: 0.2, Max: 0.4, Diff: 0.4, Sum: 4.7]
          [Processed Buffers: Min: 0, Avg: 2.3, Max: 5, Diff: 5, Sum: 54]
       [Scan RS (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 2.2]
       [Code Root Scanning (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.0]
       [Object Copy (ms): Min: 1.7, Avg: 1.7, Max: 1.8, Diff: 0.1, Sum: 40.2]
       [Termination (ms): Min: 0.0, Avg: 0.0, Max: 0.0, Diff: 0.0, Sum: 0.6]
       [GC Worker Other (ms): Min: 0.0, Avg: 0.1, Max: 0.2, Diff: 0.2, Sum: 1.8]
       [GC Worker Total (ms): Min: 2.5, Avg: 2.6, Max: 2.8, Diff: 0.3, Sum: 60.9]
       [GC Worker End (ms): Min: 1085394283.9, Avg: 1085394284.0, Max: 1085394284.1, Diff: 0.2]
    [Code Root Fixup: 0.1 ms]
    [Code Root Migration: 0.1 ms]
    [Code Root Purge: 0.0 ms]
    [Clear CT: 0.4 ms]
    [Other: 31.9 ms]
       [Choose CSet: 0.0 ms]
       [Ref Proc: 30.1 ms]
       [Ref Enq: 0.1 ms]
       [Redirty Cards: 0.0 ms]
       [Free CSet: 0.7 ms]
    [Eden: 610.0M(610.0M)->0.0B(606.0M) Survivors: 4096.0K->8192.0K Heap: 892.9M(1024.0M)->287.6M(1024.0M)]
  [Times: user=0.10 sys=0.01, real=0.03 secs]
 2015-08-06T09:44:02.673-0400: 1085394.317: Total time for which application threads were stopped: 0.0359503 seconds
 2015-08-06T09:44:07.515-0400: 1085399.158: Total time for which application threads were stopped: 0.0002921 seconds

这只是摘录，对于任何GC Pause （年轻或混合），我都看不到是什么导致了GC。 当我使用CMS它确实提供了GC原因，例如，这是使用CMS应用摘录

 2015-08-09T15:15:01.665-0400: 1364453.068: [Full GC (System.gc()) 1364453.068: [CMS: 44751K->44753K(537408K), 0.0816661 secs] 135985K->44753K(920832K), [Metaspace: 37944K->37944K(1083392K)], 0.0818386 secs] [Times: user=0.08 sys=0.00, real=0.08 secs]

Answer 1

（G1疏散暂停）（年轻）

这就是原因。 伊甸园空间已满，必须收集（撤离）。

偶尔可能会看到其他（混合的，元空间已满，巨大的分配等），但是年轻的集合是最常出现的停顿。