Free up memory on centos 6?

conlustro

There was a command for centos that someone gave me on here, and I have searched through all my posts and couldn't find it. How do I free up memory on centos?

zafouhar

http://lmgtfy.com/?q=How+do+I+FREE+up+memory+on+centos

conlustro

On one of my servers I get this:

# free -m
             total       used       free     shared    buffers     cached
Mem:         64457      57268       7189          0      15259        699
-/+ buffers/cache:      41309      23147
Swap:        30717        409      30308

and on another I have this:

# free -m
             total       used       free     shared    buffers     cached
Mem:         64458      55552       8905          0         11         16
-/+ buffers/cache:      55524       8933
Swap:        19997        453      19544

There is something wrong with the last one right? It isn't caching or buffering. They both have 64gb of ram. Is there any way to force or start caching and buffering?

DalekOfSkaro

@conlustro

Run this

sync; echo 3 > /proc/sys/vm/drop_caches && echo 0 > /proc/sys/vm/drop_caches

and then try free -m again. See if it helps.

Chances are some of this is cached memory. You can also run top or htop to see what processes are consuming the majority of your memory.

AlbaHost

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

conlustro

Thanks a lot for that, I guess that is the only way.

Janevski

http://www.linuxatemyram.com/

It's quite a nice site explaining Linux RAM usage.

Pwner

@Janevski said:

http://www.linuxatemyram.com/

It's quite a nice site explaining Linux RAM usage.

@linuxthefish

conlustro

Hi saw that one Janevski thanks. I have two servers setup exactly the same way but the ram is behaving differently I checked the make and speed of both servers and they seem to match up, but one servers seems to buffer much better than the other, I don't know what's going on.

virtualizor

Are you referring to freeing up ram on the host node or a VM ?

ATHK

@virtualizor said:
Are you referring to freeing up ram on the host node or a VM ?

Looking at the free output one would assume a node.. 64 GB RAM although it could just be a dedicated server with no virtualization

conlustro

And the prize goes to ATHK! It's a host node. I ran the above command and it seems like i't doing pretty good now. Would a soft raid1 affect the CPU or RAM usage?

ATHK

@conlustro said:
And the prize goes to ATHK! It's a host node. I ran the above command and it seems like i't doing pretty good now. Would a soft raid1 affect the CPU or RAM usage?

Yay!!!! I would like to thank everybody thank you thank you..

dankao

There are three options available to flush cache of linux memeory. Use one of below as per your requirements.

1. To free pagecache, dentries and inodes in cache memory

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

2. To free dentries and inodes use following command

sync; echo 2 > /proc/sys/vm/drop_caches

3. To free pagecache only use following command

sync; echo 1 > /proc/sys/vm/drop_caches