[root@server test]# cat /proc/sys/vm/drop_caches
0
首先,/proc/sys/vm/drop_caches的值,默认为0
[root@server test]# sync
手动执行sync命令(描述:sync 命令运行 sync 子例程。假如必须停止系统，则运行 sync 命令以确保文档系统的完整性。sync 命令将任何未写的系统缓冲区写到磁盘中，包含已修改的 i-node、已延迟的块 I/O 和读写映射文档)
[root@server test]# echo 3 > /proc/sys/vm/drop_caches
[root@server test]# cat /proc/sys/vm/drop_caches
3
将/proc/sys/vm/drop_caches值设为3
[root@server test]# free -m
total used free shared buffers cached
Mem: 249 66 182 0 0 11
-/ buffers/cache: 55 194
Swap: 511 0 511
再来运行free命令,发现现在的used为66MB,free为182MB,buffers为0MB,cached为11MB.那么有效的释放了buffer和cache.
有关/proc/sys/vm/drop_caches的用法在下面进行了说明
/proc/sys/vm/drop_caches (since Linux 2.6.16)
Writing to this file causes the kernel to drop clean caches,
dentries and inodes from memory, causing that memory to become
free.
To free pagecache, use echo 1 > /proc/sys/vm/drop_caches; to
free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
to free pagecache, dentries and inodes, use echo 3 >
/proc/sys/vm/drop_caches.
Because this is a non-destructive operation and dirty objects
are not freeable, the user should run sync(8) first.