Jvm 內存分析-jstat -gcutil

$ jstat -gc 25933 1000
 S0C    S1C    S0U    S1U      EC       EU        OC         OU       MC     MU    CCSC   CCSU   YGC     YGCT    FGC    FGCT     GCT   
8192.0 8192.0 576.0   0.0   16384.0  11647.5   20480.0    12803.0   12056.0 11832.9  0.0    0.0       18    0.113   0      0.000    0.113
8192.0 8192.0 576.0   0.0   16384.0  12136.1   20480.0    12803.0   12056.0 11832.9  0.0    0.0       18

jstat 的用法能夠參考博文：

http://docs.oracle.com/javase/7/docs/technotes/tools/share/jstat.html

EXAMPLES
This section presents some examples of monitoring a local JVM with a lvmid of 21891.

Using the gcutil option
This example attaches to lvmid 21891 and takes 7 samples at 250 millisecond intervals and displays the output as specified by the -gcutil option.

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.