Linux内存管理

一、如何释放buffer/cache

当buffer/cache被占用很高时（即free内存太小时），会导致性能低下，可以手工释放：

1） free -m； //查看内存使用状况

2）sync；   //将dirty内容回写硬盘

3）echo 3 /proc/sys/vm/drop_caches;

/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.