java运行情况监控

很多时候，我们需要dump出java内存，对程序的运行情况进行分析，这样，我们才能知道问题出在哪里。
我只用过jstat.

   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 collec-
       tion 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 col-
       lection it is only 7.74% utilized.

这是一个例子，对GC进行监控的，讲解的不错。