Linux --- manually release system cache

Linux --- manually release system cache

Linux --- manually release system 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 12 11 12 0 1 98 1 0

This cache is allocated by the system from the physical memory for file system read buffering. According to Linux instructions, the memory is automatically released when the system memory is insufficient. How to manually release caches:

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 shoshould run "sync" first in order to make sure allcached objects are freed.

This tunable was added in 2.6.16.

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