1、通過top 查看具體是哪個進程占用內存較多
Tasks: 65 total, 1 running, 64 sleeping, 0 stopped, 0 zombie
%Cpu(s): 2.0 us, 1.0 sy, 0.0 ni, 96.3 id, 0.3 wa, 0.0 hi, 0.3 si, 0.0 st
KiB Mem : 1016168 total, 63544 free, 824060 used, 128564 buff/cache
KiB Swap: 2047996 total, 1612356 free, 435640 used. 49916 avail Mem
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
25894 www 20 0 3080304 757036 3252 S 3.3 74.5 25:55.03 java
1 root 20 0 43300 2180 1340 S 0.0 0.2 3:20.35 systemd
2 root 20 0 0 0 0 S 0.0 0.0 0:00.43 kthreadd
3 root 20 0 0 0 0 S 0.0 0.0 12:44.14 ksoftirqd/0
5 root 0 -20 0 0 0 S 0.0 0.0 0:00.00 kworker/0:0H
7 root rt 0 0 0 0 S 0.0 0.0 0:00.00 migration/0
2、定位線程問題（通過命令查看PID 為25894 進程的線程情況）,命令：# ps p 25894 -L -o pcpu,pmem,pid,tid,time,tname,cmd
# ps p 25894 -L -o pcpu,pmem,pid,tid,time,tname,cmd %CPU %MEM PID TID TIME TTY CMD 0.0 74.4 25894 25894 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25896 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.1 74.4 25894 25897 00:01:09 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25898 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25899 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25900 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25901 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25902 00:00:00 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.1 74.4 25894 25903 00:01:18 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap 0.0 74.4 25894 25904 00:00:14 ? /App/java/jdk1.8.0_102/bin/java -Djava.util.logging.config.file=/App/tomcat_jtws-opefront/conf/logging.properties -Djava.util.logging.manager=org.ap .....................................以下部分省略..................................... # ps p 25894 -L -o pcpu,pmem,pid,tid,time,tname,cmd |wc -l 101
由此可以看到這個PID:25894的進程產生了很多線程。接下來就可以通過jstack查看內存使用的堆棧，具體可以執行 ps p 25894 -L -o pcpu,pmem,pid,tid,time,tname,cmd |wc -l 來查具體有多少線程.
3、將PID為25894的堆棧信息打印到jstack.log中，命令: #jstack -l 25894 > jstack.log
4、查看日志，有很多WAITING & TIMED_WAITING 狀態的日志信息，具體需要研發查看一下代碼的情況；
#cat jstack.log |grep -E 'WAITING|TIMED_WAITING' java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (on object monitor) java.lang.Thread.State: TIMED_WAITING (on object monitor) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: WAITING (parking) java.lang.Thread.State: WAITING (parking) java.lang.Thread.State: TIMED_WAITING (on object monitor) java.lang.Thread.State: WAITING (on object monitor) java.lang.Thread.State: WAITING (on object monitor) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking) java.lang.Thread.State: TIMED_WAITING (parking)
后經研發檢查代碼並升級程序至新版本，問題解決。
參考鏈接：https://www.javatang.com/archives/2017/10/25/36441958.html#TIMED_WAITING