Linux下Tomcat VM参数修改

不可行的方法

最初我直接修改catalina.sh, 将JAVA_OPTS变量加上了

            
                -server
                -Xms1G
                -Xmx1G
                -XX:+UserG1GC
        

最初看起来没啥问题，但是当服务器运行几天后，发现执行shutdown.sh无法关闭tomcat， 错误信息如下：

            
                # root@iZ94hjppdqzZ:~/projects/taolijie# cat hs_err_pid5519.log 
                # There is insufficient memory for the Java Runtime Environment to continue.
                # Native memory allocation (mmap) failed to map 1073741824 bytes for committing reserved memory.
                # Possible reasons:
                #   The system is out of physical RAM or swap space
                #   In 32 bit mode, the process size limit was hit
                # Possible solutions:
                #   Reduce memory load on the system
                #   Increase physical memory or swap space
                #   Check if swap backing store is full
                #   Use 64 bit Java on a 64 bit OS
                #   Decrease Java heap size (-Xmx/-Xms)
                #   Decrease number of Java threads
                #   Decrease Java thread stack sizes (-Xss)
                #   Set larger code cache with -XX:ReservedCodeCacheSize=
                # This output file may be truncated or incomplete.
                #
                #  Out of Memory Error (os_linux.cpp:2673), pid=5519, tid=3061726064
                #
                # JRE version:  (8.0_45-b14) (build )
                # Java VM: Java HotSpot(TM) Server VM (25.45-b02 mixed mode linux-x86 )
                # Failed to write core dump. Core dumps have been disabled. To enable core dumping, try "ulimit -c unlimited" before starting Java again
                #
            
        

关闭个tomcat要请求1G的内存， 当时服务器就剩下200M内存，所以Out Of Memory了。查看shutdown.sh，发现它其实还是调用了catalina.sh，只是传入了一个stop参数。而catalina.sh是执行了

            org.apache.catalina.startup.Bootstrap stop
        

来向tomcat发送关闭信息的。由于上面我们设置了JAVA_OPTS使用1G的堆，因此执行该类时JVM会向系统申请1G多的内存，直接导致Out Of Memory。

可行的方法

在catalina.sh的第二行添加：

            CATALINA_OPTS="$CATALINA_OPTS -server -Xms1G -Xmx1G -XX:+UseG1GC"
        

这些VM参数就会只应用到catalina而不是所有Tomcat进程。

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