linux释放内存

0 Problem

跑实验的时候，ctrl+c中断后free -m发现used占用太多，64G内存占用了50多G，其中有48G的cached，cached占用太大，久久不消。

（Cache，译作“缓存”，指 CPU 和内存之间高速缓存。Buffer，译作“缓冲区”，指在写入磁盘前的存储再内存中的内容）

 

1 Solution

清理caches

sync　# 强制被改变的内容写入磁盘。通常不需sync，系统会自动写入。

echo 3 > /proc/sys/vm/drop_caches　# 释放cache。

 

2 Explanation

Writing to this will cause the kernel to drop clean caches, dentries and inodes from memory, causing that memory to become free.

To free pagecache:
* echo 1 > /proc/sys/vm/drop_caches

To free dentries and inodes:　
* echo 2 > /proc/sys/vm/drop_caches

To free pagecache, dentries and inodes:
* echo 3 > /proc/sys/vm/drop_caches

As this is a non-destructive operation, and dirty objects are notfreeable, the user should run "sync" first in order to make sure allcached objects are freed.
This tunable was added in 2.6.16.