/proc/sys/vm/drop_caches用法说明

/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 first.