1. 使用方法
/proc/sys/vm/drop_caches默认是0
# echo 1 > /proc/sys/vm/drop_caches; free pagecache, use
# echo 2 > /proc/sys/vm/drop_caches; free dentries and inodes
# echo 3 > /proc/sys/vm/drop_caches; free pagecache, dentries and inodes
注意：使用之前需要先sync，将缓存刷到磁盘中。
2. 实验
单位：MB # free -m
total used free shared buff/cache available
Mem: 79
Swap:
# cp /etc/* /mytest/
# free -m
total used free shared buff/cache available
Mem: 1825 382 1341 8 1412
Swap: 0 0 0 过一段时间： # free -m
total used free shared buff/cache available
Mem: 1825 382 1341 8 1412
Swap: 0 # cat /proc/sys/vm/drop_caches
0 # sync # echo 3 > /proc/sys/vm/drop_caches
# free -m
total used free shared buff/cache available
Mem: 1825 382 1405 8 1413
Swap:
3. 写个脚本做这个事情
# cat cleanup_cache.sh
#!/bin/sh
# drop_caches for every mins drop_caches() {
echo "Drop caches."
sync
echo > /proc/sys/vm/drop_caches &
return
} while true; do
sleep
drop_caches
done exit
4. 结论
Linux内核默认保持drop_cache的值是0，不建议经常修改它。