1、手动清理内存和Cache方法

Linux下清理内存和Cache方法 /proc/sys/vm/drop_caches

频繁的文件访问会导致系统的Cache使用量大增

$ free -m
total used free shared buffers cached
Mem: 3955 3926 28 0 55 3459
-/+ buffers/cache: 411 3544
Swap: 5726 0 5726

free内存减少到几十兆，系统运行缓慢

运行sync将dirty的内容写回硬盘

清理内存和Cache方法：

echo 1 > /proc/sys/vm/drop_caches

echo 2 > /proc/sys/vm/drop_caches

echo 3 > /proc/sys/vm/drop_caches

2、自动清理内存和Cache方法，使用脚本自动清理

#!/bin/bash
# 清理系统缓存脚本
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 500 ];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
fi