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Clearing cached memory on linux

Posted on 2009-06-29
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2,067 Views
Last Modified: 2012-05-07
Hello i want to clear cached memory on Red Hat Enterprise Linux AS release 3 (Taroon)
echo 3 > /proc/sys/vm/drop_caches - doesnt work.
uname -a
Linux ivision 2.4.21-4.ELsmp #1 SMP Fri Oct 3 17:52:56 EDT 2003 i686 i686 i386 GNU/Linux

have u any advice for me?
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Question by:_Amanat_
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Expert Comment

by:astroviper
ID: 24742378
You are running that as superuser/root user right?
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Author Comment

by:_Amanat_
ID: 24742383
yes
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Expert Comment

by:astroviper
ID: 24742387
http://www.linuxinsight.com/proc_sys_vm_drop_caches.html

To free pagecache, dentries and inodes: echo 3 > /proc/sys/vm/drop_caches
 
As this is a non-destructive operation, and dirty objects are not freeable, the user should run "sync" first in order to make sure all cached objects are freed.

Try the following as superuser:

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

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Author Comment

by:_Amanat_
ID: 24742408
echo 1 > /proc/sys/vm/drop_caches
-bash: /proc/sys/vm/drop_caches: No such file or directory
[root@ivision root]#
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Accepted Solution

by:
astroviper earned 250 total points
ID: 24742453
Ah okay, its a just Red Hat thing. From what I'm reading though is there any real need to clear it?

From: How to find the actual memory usage on Redhat Linux
"The answer is simple - linux kernel takes *all* RAM for bufferes/cache, but release it if some applications ask for memory."

"Yes, that is right, Linux will try to use 100% of memory always, if not used by programs, will be used as buffer/cache.
Use the "free" command to identify the memory used by programs and as buffer/cache. The values under +/- buffers/cache gives you the real memory usage."

Memory Utilisation on Red Hat Enterprise linux

This question seems to have been asked around a few times and the consensus reply seems to be "oh, but you don't need to."
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