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free up memory

Terminal - free up memory
echo 3 > /proc/sys/vm/drop_caches
2012-08-05 19:35:14
User: andreisid
Functions: echo
free up memory


There are 4 alternatives - vote for the best!

Terminal - Alternatives
sync; echo 3 | sudo tee /proc/sys/vm/drop_caches
2010-05-23 11:39:35
User: bandie91
Functions: echo sudo sync tee

where proc filesystem mounted under /proc

sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
sync; echo 3 > /proc/sys/vm/drop_caches
sysctl -w vm.drop_caches=3
sudo sync && sudo echo 3 | sudo tee /proc/sys/vm/drop_caches
2012-03-17 08:27:58
User: StephenJudge
Functions: echo sudo sync tee
Tags: memory cache

"That's it. Not much to see here. The first command writes any cache data that hasn't been written to the disk out to the disk. The second command tells the kernel to drop what's cached. Not much to it. This invalidates the write cache as well as the read cache, which is why we have the sync command first. Supposedly, it is possible to have some cached write data never make it to disk, so use it with caution, and NEVER do it on a production server. You could ... but why take the risk?

As long as you are running a post 2.6.16 kernel,..."

Source: http://ubuntuforums.org/showpost.php?p=3621283&postcount=1

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What others think

Better use sysctl instead of echo :

/sbin/sysctl vm.drop_caches=3o

1 --> to free pagecache

2 --> to free dentries and inodes

3 --> to free pagecache, dentries and inodes

Comment by jlaunay 138 weeks and 1 day ago

Why would calling sysctl be better than calling echo?

Comment by wr8cr8 137 weeks and 6 days ago

There is no big difference but with echo you can make a mistake, for example echo 4 or any bad value will work but sysctl is a tool especially designed to configure kernel parameters:

/sbin/sysctl -w vm.drop_caches=4

sysctl: setting key "vm.drop_caches": Argument invalide

vm.drop_caches = 4

Sysctl also allow you to edit /etc/sysctl.conf to make the change permanent.

Comment by jlaunay 137 weeks and 6 days ago

Your point of view

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