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I haven't even set up my website on my dedicated server so I'm the only one using it at the moment. And yet this is what I see in my sys info:

alt text Full Size

I just got a bunch of security softwares installed today so I'm wondering if that could be the reason. Programs like Dos deflate, CSF firewall, Mod_security, SIM, Log watch, etc.

My server's details:

CentOS  
Processor       Intel Xeon CPU X3220  
CPU Speed       2.39 GHz  
Cache Size      4.00 MB  
RAM             2GB DDR2
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4 Answers 4

Another tool to use is free:

<~> $ free
             total       used       free     shared    buffers     cached
Mem:       4148872    3969128     179744          0     160308    3125864
-/+ buffers/cache:     682956    3465916
Swap:      2144652       5172    2139480

The first line mirrors what you see, that only 179M is free. The second line shows the real number, 3.465G, with all buffers and cache removed.

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Your picture shows 56% cached memory. Linux works with kernel and cache loaded in the RAM to speed up things. When you have more applications taking up memory, the cache will be reduced to trade off its advantages for running more apps.

In short, things are fine; you are not running out of memory.
The Kernel+Apps memory utilization is near the 30% mark.

Update: sebthebert gave this nice link to LinuxAteMyRam for more reading on the subject.

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3  
Exactly right. UNIX, Linux and MacOS X all think that free memory is wasted memory and tries to spend it all on cache. –  Roy Oct 10 '09 at 7:16
2  
@Roy, even Windows does this as of Vista/2008. I have 3GB in my laptop, at the moment there's about 8MB free, and more than 1.5GB is cached. –  ThatGraemeGuy Oct 10 '09 at 8:13
    
For more information about that: linuxatemyram.com –  sebthebert Oct 10 '09 at 21:53

There's nothing wron with that picture. My server with 768M RAM routinely sits at or near 100% utilization - even when the load averages are 0.01 0.01 0.01 and the busiest process is top.

If, after running your server with its "real" load, it's running out of memory, that's when you start worrying :)

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Load averages have nothing to do with memory usage. –  Juliano Oct 11 '09 at 13:12
    
that's my point, actually - memory usage is only one component, and one not really to worry about unless your CPU or disk I/O is getting hammered as well –  warren Oct 11 '09 at 14:40

It's using 600MB of memory at the moment - you must have quite a few things running, but it's not unreasonable.

Ignore the 'buffers' and 'cached' lines - those are disk buffers and disk cache. The system's just using that because it's there.

Look at the 'Kernel + Applications' line to see what the programs are actually using.

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