Tomcat OutOfMemory问题: java.lang.OutOfMemoryError: GC overhead limit exceeded

问题 :

Caused by: java.lang.OutOfMemoryError: GC overhead limit exceeded

问题产生原因：

根据 sun 的说法： “if too much time is being spent in garbage collection: if more than 98% of the total time is spent in garbage collection and less than 2% of the heap is recovered, an OutOfMemoryError will be thrown.”

jvm gc 行为中超过98% 以上的时间去释放小于 2% 的堆空间时会报这个错误。

处理方法：

Sun 官方申明：

The parallel / concurrent collector will throw an OutOfMemoryError if too much time is being spent in garbage collection: if more than 98 ％ of the total time is spent in garbage collection and less than 2％ of the heap is recovered ， an OutOfMemoryError will be thrown. This feature is designed to prevent applications running for an extended period of time while making little or no progress because the heap is too small. If necessary ，this feature can be disabled by adding the option -XX:-UseGCOverheadLimit to the command line.

在jvm 启动参数中添加 “-XX:-UseGCOverheadLimit” ，该参数在JDK6 中默认启用 (“-XX:+UseGCOverheadLimit”) 。

调整后的生产环境中使用的参数为：

JAVA_OPTS='-Xms512m -Xmx4096m -XX:MaxPermSize=128m -XX:-UseGCOverheadLimit -XX:+UseConcMarkSweepGC'

检查是否有使用了大量内存的代码或死循环

使用jstat 命令监控 gc 行为是否正常

jstat监控 gc 的命令格式为：

stat -gcutil [-t] [-h] [ []]

mid为 JVM 进程id ，可以用 ps -ef 或 jps -lv 命令查找。

以下命令为每 1秒钟输出一次 gc 状态，共输入 5次

S0 S1 E O P YGC YGCT FGC FGCT GCT

0.00 93.34 85.63 82.95 59.73 1085 33.351 58 4.396 37.748

98.42 0.00 31.89 83.52 59.73 1088 33.487 58 4.396 37.883

100.00 85.65 100.00 84.08 59.73 1091 33.554 58 4.396 37.950

0.00 100.00 54.30 84.49 59.73 1093 33.660 58 4.396 38.057

98.25 0.00 10.46 85.11 59.73 1096 33.768 58 4.396 38.164

经过一段时间的观察 ,确认是否正确