cache 초기화

## drop cache
echo 1 > /proc/sys/vm/drop_caches
## drop inode/dentry
echo 2 > /proc/sys/vm/drop_caches

### reclaim cache
echo 1000~10000 > /proc/sys/vm/vfs_cache_pressure

vi /etc/sysctl.conf
  vm.vfs_cache_pressure=1000~10000
sysctl -p