在linux环境下配置tomcat的垃圾回收的一些配置，在catalina.sh文件的开头，直接加入

JAVA_OPTS="

$JAVA_OPTS

-server

-Xms64m -Xmx512m

-XX:PermSize=64M -XX:MaxPermSize=128m

-XX:+HeapDumpOnOutOfMemoryError  -XX:HeapDumpPath=/home/dump.hprof

-verbose:gc  -Xloggc:/home/gc.log -XX:+PrintGCDetails -XX:+PrintGCApplicationStoppedTime

-XX:+PrintGCDateStamps -XX:+PrintHeapAtGC"

解释一下用处

$JAVA_OPTS是引入以前的配置信息

-server 是只服务器

-Xms64m -Xmx512m 堆内存的最小最大空间

-XX:PermSize=64M -XX:MaxPermSize=128m 栈空间的最小最大

-XX:+HeapDumpOnOutOfMemoryError  -XX:HeapDumpPath=/home/dump.hprof 出现了内存溢出，将当时的快照信息写入到dump.hprof文件

-verbose:gc gc的一些配置

-Xloggc:/home/gc.log  每次gc写入gc.log日志中

-XX:+PrintGCDetails 打印gc详情

-XX:+PrintGCApplicationStoppedTime 打印垃圾回收时，应用暂停的时间

-XX:+PrintGCDateStamps  输出gc的时间戳

-XX:+PrintHeapAtGC  打印GC前后的详细堆栈信息

贴一段gc信息日志

Total time for which application threads were stopped: 0.0000750 seconds

{Heap before GC invocations=1 (full 0):

PSYoungGen      total 19136K, used 16448K [0x00000000f5560000, 0x00000000f6ab0000, 0x0000000100000000)

eden space 16448K, 100% used [0x00000000f5560000,0x00000000f6570000,0x00000000f6570000)

from space 2688K, 0% used [0x00000000f6810000,0x00000000f6810000,0x00000000f6ab0000)

to   space 2688K, 0% used [0x00000000f6570000,0x00000000f6570000,0x00000000f6810000)

PSOldGen        total 43712K, used 0K [0x00000000e0000000, 0x00000000e2ab0000, 0x00000000f5560000)

object space 43712K, 0% used [0x00000000e0000000,0x00000000e0000000,0x00000000e2ab0000)

PSPermGen       total 65536K, used 12915K [0x00000000dc000000, 0x00000000e0000000, 0x00000000e0000000)

object space 65536K, 19% used [0x00000000dc000000,0x00000000dcc9cf30,0x00000000e0000000)

2018-05-24T15:39:06.084+0800: 0.424: [GC [PSYoungGen: 16448K->2336K(19136K)] 16448K->2336K(62848K), 0.0034480 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]

Heap after GC invocations=1 (full 0):

PSYoungGen      total 19136K, used 2336K [0x00000000f5560000, 0x00000000f6ab0000, 0x0000000100000000)

eden space 16448K, 0% used [0x00000000f5560000,0x00000000f5560000,0x00000000f6570000)

from space 2688K, 86% used [0x00000000f6570000,0x00000000f67b8050,0x00000000f6810000)

to   space 2688K, 0% used [0x00000000f6810000,0x00000000f6810000,0x00000000f6ab0000)

PSOldGen        total 43712K, used 0K [0x00000000e0000000, 0x00000000e2ab0000, 0x00000000f5560000)

object space 43712K, 0% used [0x00000000e0000000,0x00000000e0000000,0x00000000e2ab0000)

PSPermGen       total 65536K, used 12915K [0x00000000dc000000, 0x00000000e0000000, 0x00000000e0000000)

object space 65536K, 19% used [0x00000000dc000000,0x00000000dcc9cf30,0x00000000e0000000)

}

2018-05-24T15:39:06.084+0800: 0.424: [GC [PSYoungGen: 16448K->2336K(19136K)] 16448K->2336K(62848K), 0.0034480 secs] [Times: user=0.01 sys=0.00, real=0.01 secs]

发生了gc

将内存dump下来

jmap -dump:format=b,file=/applis/dump.hprof pid号