2023年11月26日发(作者：)

Linux下清理内存和Cache方法

频繁的文件访问会导致系统的Cache使用量大增

$ free -m

total used free shared buffers cached

Mem: 3955 3926 28 0 55 3459

-/+ buffers/cache: 411 3544

Swap: 5726 0 5726

free内存减少到几十兆，系统运行缓慢

运行sync将dirty的内容写回硬盘

$sync

通过修改proc系统的drop_caches清理free的cache

$echo 3 > /proc/sys/vm/drop_caches

drop_caches的详细文档如下：

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.

修改/etc/ 添加如下选项后就不会内存持续增加

_ratio = 1

_background_ratio=1

_writeback_centisecs=2

_expire_centisecs=3

_caches=3

ness =100

_cache_pressure=163