GC输出澄清

Question

我正在运行具有以下设置的Java应用程序:
-XX:+ CMSParallelRemarkEnabled
-XX:+ UseConcMarkSweepGC
-XX:+ UseParNewGC
-XX:+ PrintGCApplicationStoppedTime
-XX:+ PrintGCApplicationConcurrentTime
-XX:+ PrintGCDetails
-XX:+ PrintGCTimeStamps
-XX: + PrintGCDateStamps
-XX:+ PrintHeapAtGC
-XX:+ PrintTenuringDistribution

我不确定如何解释相关的gc日志(如下).特别是:

• GC调用= 31(满3)后的堆:这是否意味着有31个小的GC和3个完整的GC？

• 什么触发应用程序线程停止的几个连续行总时间和应用程序时间？是否有可能获得与这些线相关的时间戳？

GC日志:

Total time for which application threads were stopped: 0.0046910 seconds  
Application time: 0.7946670 seconds  
Total time for which application threads were stopped: 0.0002900 seconds  
Application time: 1.0153640 seconds  
Total time for which application threads were stopped: 0.0002780 seconds  
Application time: 1.0161890 seconds  
Total time for which application threads were stopped: 0.0002760 seconds  
Application time: 1.0145990 seconds  
Total time for which application threads were stopped: 0.0002950 seconds  
Application time: 0.9999800 seconds  
Total time for which application threads were stopped: 0.0002770 seconds  
Application time: 1.0151640 seconds
Total time for which application threads were stopped: 0.0002730 seconds
Application time: 0.9996590 seconds  
Total time for which application threads were stopped: 0.0002880 seconds  
Application time: 0.9624290 seconds  

{Heap before GC invocations=30 (full 3):  
 par new generation   total 131008K, used 130944K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000)  
  eden space 130944K, 100% used [0x00000000eac00000, 0x00000000f2be0000, 0x00000000f2be0000)  
  from space 64K,   0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000)  
  to   space 64K,   0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000)  
 concurrent mark-sweep generation total 131072K, used 48348K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000)  
 concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000)  

2010-05-11T09:30:13.888+0100: 384.955: [GC 384.955: [ParNew  
Desired survivor size 32768 bytes, new threshold 0 (max 0)  
: 130944K->0K(131008K), 0.0052470 secs] 179292K->48549K(262080K), 0.0053030 secs] [Times: user=0.00 sys=0.00, real=0.01 secs]  

Heap after GC invocations=31 (full 3):  
 par new generation   total 131008K, used 0K [0x00000000eac00000, 0x00000000f2c00000, 0x00000000f2c00000)  
  eden space 130944K,   0% used [0x00000000eac00000, 0x00000000eac00000,   0x00000000f2be0000)
  from space 64K,   0% used [0x00000000f2be0000, 0x00000000f2be0000, 0x00000000f2bf0000)  
  to   space 64K,   0% used [0x00000000f2bf0000, 0x00000000f2bf0000, 0x00000000f2c00000)  
 concurrent mark-sweep generation total 131072K, used 48549K [0x00000000f2c00000, 0x00000000fac00000, 0x00000000fac00000)  
 concurrent-mark-sweep perm gen total 30000K, used 19518K [0x00000000fac00000, 0x00000000fc94c000, 0x0000000100000000)  
}

Total time for which application threads were stopped: 0.0056410 seconds  
Application time: 0.0475220 seconds  
Total time for which application threads were stopped: 0.0001800 seconds  
Application time: 1.0174830 seconds  
Total time for which application threads were stopped: 0.0003820 seconds  
Application time: 1.0126350 seconds  
Total time for which application threads were stopped: 0.0002750 seconds  
Application time: 1.0155910 seconds
Total time for which application threads were stopped: 0.0002680 seconds
Application time: 1.0155580 seconds  
Total time for which application threads were stopped: 0.0002880 seconds  
Application time: 1.0155480 seconds  
Total time for which application threads were stopped: 0.0002970 seconds  
Application time: 0.9896810 seconds  

Answer 1

那些没有时间戳的行不是GC事件，它们记录安全点发生的时间以及持续的时间。在 6u21 之前，它们有些不可靠。