检查有哪些应用占用过高
[root@javaserver data]# ps auxw|head -1;ps auxw|sort -rn -k4|head -10 USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 5664 0.3 30.7 11015560 10090616 ? Ssl 2019 1353:17 /usr/sbin/rsyslogd -n root 27798 0.7 6.7 14238824 2206032 pts/2 Ssl+ 14:16 4:25 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 9449 0.4 6.6 14264364 2188920 pts/4 Ssl+ 04:20 5:16 /docker-java-home/jre/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 15941 0.5 6.0 14255300 1983220 pts/5 Ssl+ 04:30 6:36 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 5479 0.4 5.9 14195016 1952560 pts/3 Ssl+ 04:15 5:39 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 12842 0.5 5.7 14279004 1871372 pts/6 Ssl+ 04:25 6:33 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 19234 1.6 3.7 14244980 1216372 pts/0 Ssl+ 04:35 19:19 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start root 1969 1.0 2.6 14203240 856308 pts/1 Ssl+ 04:10 12:45 /usr/local/openjdk-8/bin/java -Djava.util.logging.config.file=/usr/local/tomcat/conf/logging.properties -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager -Djdk.tls.ephemeralDHKeySize=2048 -Djava.protocol.handler.pkgs=org.apache.catalina.webresources -Dorg.apache.catalina.security.SecurityListener.UMASK=0027 -Dignore.endorsed.dirs= -classpath /usr/local/tomcat/bin/bootstrap.jar:/usr/local/tomcat/bin/tomcat-juli.jar -Dcatalina.base=/usr/local/tomcat -Dcatalina.home=/usr/local/tomcat -Djava.io.tmpdir=/usr/local/tomcat/temp org.apache.catalina.startup.Bootstrap start polkitd 28018 0.1 1.2 3044596 400996 pts/7 Ssl+ 04:00 1:46 mysqld --character-set-server=utf8mb4 --collation-server=utf8mb4_unicode_ci root 2511 1.7 0.2 155048 89120 ? Ss 2019 6381:52 /usr/lib/systemd/systemd-journald
发现了占用最高的是叫 rsyslogd 应用，用去了超过 30% 的内存。原来 rsyslogd 是linux系统自带的日志管理工具。
可以使用以下命令查看是否有启动该应用
[root@javaserver data]# ps aux | grep "rsyslog" | grep -v "grep" root 15527 0.3 0.0 792608 9856 ? Ssl 23:48 0:00 /usr/sbin/rsyslogd -n
限制 rsyslogd 的内存占用
[root@javaserver data]# vi /usr/lib/systemd/system/rsyslog.service # 添加下面配置项，最高限制为 80M [Service] MemoryAccounting=yes MemoryMax=80M MemoryHigh=8M [root@javaserver ~]# systemctl daemon-reload [root@javaserver ~]# systemctl restart rsyslog