linux的 内存 cached 释放

用free命令查看内存时，发现cached占用量过大。
释放脚本如下：

#!/bin/bash

used=`free -m | awk 'NR==2' | awk '{print $3}'`
free=`free -m | awk 'NR==2' | awk '{print $4}'`

echo "===========================" >> /var/log/mem.log
date >> /var/log/mem.log
echo "Memory usage | [Use：${used}MB][Free：${free}MB]" >> /var/log/mem.log

if [ $free -le 100 ] ; then
                sync && echo 1 > /proc/sys/vm/drop_caches
                sync && echo 2 > /proc/sys/vm/drop_caches
                sync && echo 3 > /proc/sys/vm/drop_caches
                echo "OK" >> /var/log/mem.log
else
                echo "Not required" >> /var/log/mem.log

将脚本保存到 /root/systemtools/freemem.sh
将脚本添加到crond任务，定时执行:

# echo "*/30 * * * * root /root/systemtools/freemem.sh" >> /etc/crontab