JVM性能调优3：JVM_堆溢出分析过程和命令



本系列包括：

JVM性能调优1：JVM性能调优理论及实践（收集整理）

JVM性能调优2：JVM性能调优参数整理

JVM性能调优3：JVM_堆溢出分析过程和命令

JVm性能调优4：GC日志分析

JVM性能调优5：Heap堆分析方法

1    查看JVM状态信息jstat命令格式

        jstat-option -t -h num pid interval count

        -option:参数

        -t打印收集信息的时间

        -h每num行打印一个head

        pid监控的进程号

        interval间隔多少毫秒采集一次信息

        count一共采集多少次信息。

2    分析过程命令

        (1)查看JVM启动参数和进程号

                  jps -mlvV

        (2)看堆内存分配情况

                  jstat -gccapacity -t -h 5 2808 100 10

 

        (3)看垃圾回收情况

                  jstat -gcutil -t -h 5 2808 100 10

                  jstat -gccause -t -h 5 2808 100 10

                  

                  -gcutil:查看堆内存占用和回收情况。

                  -gccause:查看最近一次垃圾回收原因。

 

 (4)如果堆内存持续占用率很高，查看堆内存内对象情况

     jmap-histo pid

     

 (5)如果向查看更多信息，在cmd里运行jstat查看jstat的其他参数。

 

 (6)更多的资料信息，请上网查询查找。

 

3    附录

（1）jstat –gccapacity 输出结果

Column	Description
NGCMN	Minimum new generation capacity (KB).
NGCMX	Maximum new generation capacity (KB).
NGC	Current new generation capacity (KB).
S0C	Current survivor space 0 capacity (KB).
S1C	Current survivor space 1 capacity (KB).
EC	Current eden space capacity (KB).
OGCMN	Minimum old generation capacity (KB).
OGCMX	Maximum old generation capacity (KB).
OGC	Current old generation capacity (KB).
OC	Current old space capacity (KB).
PGCMN	Minimum permanent generation capacity (KB).
PGCMX	Maximum Permanent generation capacity (KB).
PGC	Current Permanent generation capacity (KB).
PC	Current Permanent space capacity (KB).
YGC	Number of Young generation GC Events.
FGC	Number of Full GC Events.

（2）jstat –util 输出结果

Column	Description
S0	Survivor space 0 utilization as a percentage of the space's current capacity.
S1	Survivor space 1 utilization as a percentage of the space's current capacity.
E	Eden space utilization as a percentage of the space's current capacity.
O	Old space utilization as a percentage of the space's current capacity.
P	Permanent space utilization as a percentage of the space's current capacity.
YGC	Number of young generation GC events.
YGCT	Young generation garbage collection time.
FGC	Number of full GC events.
FGCT	Full garbage collection time.
GCT	Total garbage collection time.

（3）jstat –gccause

Column	Description
LGCC	Cause of last Garbage Collection.
GCC	Cause of current Garbage Collection.

 

（4）jstat –gc

Column	Description
S0C	Current survivor space 0 capacity (KB).
S1C	Current survivor space 1 capacity (KB).
S0U	Survivor space 0 utilization (KB).
S1U	Survivor space 1 utilization (KB).
EC	Current eden space capacity (KB).
EU	Eden space utilization (KB).
OC	Current old space capacity (KB).
OU	Old space utilization (KB).
PC	Current permanent space capacity (KB).
PU	Permanent space utilization (KB).
YGC	Number of young generation GC Events.
YGCT	Young generation garbage collection time.
FGC	Number of full GC events.
FGCT	Full garbage collection time.
GCT	Total garbage collection time.