Linux--- 手工釋放系統cache

Linux--- 手工釋放系統cache

Linux--- 手工釋放系統cache

linux:/etc/rc.d # vmstat

procs -----------memory---------- ---swap-- -----io---- -system-- -----cpu------

 r  b  swpd  free  buff  cache  si  so    bi    bo  in  cs us sy id wa st

 0  0      0 4205280  14880 2598540    0    0    0    12  11  12  0  1 98  1  0

這個cache是系統從實體記憶體分配一塊，用來做檔案系統的讀緩衝，按照Linux的說明在系統記憶體緊張時，這個記憶體是會自動釋放的。手工釋放caches的方法：

sync;echo 3>/proc/sys/vm/drop_caches

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.

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