jstat 分析应用垃圾回收状况

jstat -gcutil 21891 250 7 

  S0     S1     E      O      P     YGC    YGCT    FGC    FGCT     GCT 

12.44   0.00  27.20   9.49  96.70    78    0.176     5    0.495    0.672 

12.44   0.00  62.16   9.49  96.70    78    0.176     5    0.495    0.672 

12.44   0.00  83.97   9.49  96.70    78    0.176     5    0.495    0.672 

  0.00   7.74   0.00   9.51  96.70    79    0.177     5    0.495    0.673 

  0.00   7.74  23.37   9.51  96.70    79    0.177     5    0.495    0.673 

  0.00   7.74  43.82   9.51  96.70    79    0.177     5    0.495    0.673 

  0.00   7.74  58.11   9.51  96.71    79    0.177     5    0.495    0.673 

 

The output of this example shows that a young generation collection occurred between the 3rd and 4th sample. The collection took 0.001 seconds and promoted objects from the eden space (E) to the old space (O), resulting in an increase of old space utilization from 9.49% to 9.51%. Before the collection, the survivor space was 12.44% utilized, but after this collection it is only 7.74% utilized.