查看程序占用tomcat内存情况 - smile0821/learngit GitHub Wiki

最近，公司线上tomcat经常无缘无辜宕机，总结了一下定位问题的方法，仅供参考：
报错信息：
Maximum number of threads (200) created for connector with address null and port 9443

1. There is insufficient memory for the Java Runtime Environment to continue.
2. Cannot create GC thread. Out of system resources.
   一、查看当前用户线程和文件句柄数是否超出限制
   （1）显示当前用户进程限制：ulimit -a 
   显示结果：
   core file size (blocks, -c) 0
   data seg size (kbytes, -d) unlimited
   scheduling priority (-e) 0
   file size (blocks, -f) unlimited
   pending signals (-i) 256612
   max locked memory (kbytes, -l) 64
   max memory size (kbytes, -m) unlimited
   open files (-n) 102400
   pipe size (512 bytes, -p) 8
   POSIX message queues (bytes, -q) 819200
   real-time priority (-r) 0
   stack size (kbytes, -s) 10240
   cpu time (seconds, -t) unlimited
   max user processes (-u) 1024
   virtual memory (kbytes, -v) unlimited
   file locks (-x) unlimited
   （2）修改所有 linux 用户的环境变量文件：
   vi /etc/profile
   ulimit -u 10000
   ulimit -n 4096
   保存后运行#source /etc/profile 使其生效
   二、查看当前端口号进程信息和GC使用情况
   （1）显示端口的PID：lsof -i:端口
   示例：lsof -i:7074
   COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
   java 3195 ligang 34u IPv4 37416693 0t0 TCP *:7074 (LISTEN)
   （2）gc信息统计：jstat -gcutil PID
   示例：jstat -gcutil 3195
   S0 S1 E O P YGC YGCT FGC FGCT GCT
   12.63 0.00 52.03 78.63 99.13 4148 24.274 200 40.246 64.520
   （3）输出线程数：ps -mp PID -o THREAD,tid,time | wc -l
   示例：ps -mp 3195 -o THREAD,tid,time | wc -l
   43
   三、查看进程内存使用情况及定位到对应程序
   （1）内存使用情况：top -p PID
   示例：top 3195
   top – 15:29:27 up 25 days, 20:05, 2 users, load average: 0.01, 0.05, 0.01
   Tasks: 1 total, 0 running, 1 sleeping, 0 stopped, 0 zombie
   Cpu(s): 0.0%us, 0.1%sy, 0.0%ni, 99.8%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st
   Mem: 8058868k total, 6821684k used, 1237184k free, 181936k buffers
   Swap: 2097144k total, 492300k used, 1604844k free, 1897320k cached

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
3195 ligang 20 0 4862m 196m 10m S 0.0 2.5 7:57.48 java
（2）找到该进程后，如何定位具体线程或代码呢，首先显示线程列表,并按照CPU占用高的线程排序：
ps mp PID -o THREAD,tid,time | sort -rn | head -10
示例：ps -mp PID -o THREAD,tid,time | sort -rn | head -10
USER %CPU PRI SCNT WCHAN USER SYSTEM TID TIME
ligang 0.6 – – - – – – 00:07:58
ligang 0.2 19 – futex_ – – 3270 00:02:49
ligang 0.0 19 – inet_c – – 3277 00:00:00
ligang 0.0 19 – inet_c – – 3273 00:00:00
ligang 0.0 19 – inet_c – – 3271 00:00:00
ligang 0.0 19 – inet_c – – 3203 00:00:05
ligang 0.0 19 – futex_ – – 7644 00:00:00
ligang 0.0 19 – futex_ – – 3420 00:00:00
ligang 0.0 19 – futex_ – – 3288 00:00:06
（3）将需要的线程ID转换为16进制格式：printf “%x\n” TID
示例：printf “%x\n” 3270
cc6
（4）最后打印线程的堆栈信息：jstack PID |grep cc6 -A 30
示例：
jstack 2633 |grep e18 -A 30
结果就可以看到哪段代码导致的问题…
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作者：奋飛
来源：CSDN
原文：https://blog.csdn.net/ligang2585116/article/details/46343271
版权声明：本文为博主原创文章，转载请附上博文链接！