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Ubuntu server: How can I see what processes are using memory?

Posted on 2009-07-09
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Last Modified: 2013-12-16
I'm trying to figure out what's eating all 4G of memory on my server but top/vmstat/free/ps auc, etc. aren't really telling me anything.
I can see that the system is using all the ram, but I can't tell exactly *what* is using it.
I've tried stopping mysql (which I would have thought was the culprit) but that didn't help.
If you look at the output below, top only shows mysql using 7.2% of memory...what's eating the rest of it?
Examples:
top - 19:18:03 up  6:00,  1 user,  load average: 1.06, 1.22, 1.34

Tasks: 151 total,   1 running, 150 sleeping,   0 stopped,   0 zombie

Cpu(s):  1.5%us,  3.6%sy,  0.0%ni, 73.0%id, 21.9%wa,  0.0%hi,  0.0%si,  0.0%st

Mem:   3873336k total,  3757576k used,   115760k free,     7596k buffers

Swap:  2610520k total,    17328k used,  2593192k free,  3362408k cached
 

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND

17230 mysql     20   0 1853m 271m 2504 S   16  7.2   8:00.20 mysqld

17483 root      20   0 13732  11m  944 S    1  0.3   0:11.53 syslog-ng

18395 www-data  20   0 34588  10m 4300 S    1  0.3   0:02.58 php

18424 root      20   0 34588  10m 4316 S    1  0.3   0:02.57 php

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Question by:cdukes
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stefanx earned 250 total points
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Most of your RAM is probably used in buffers that the kernel determines. You see the amount with the free command.
Keep in mind that having RAM that is not used is a waste, so having a  large amount of RAM used by buffers is pretty normal ;)

With Top (in case you don't know), you can sort the applications by memory usage by pressing M

Not what you're looking for I'm sure, but maybe slightly helpful
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by:mrjoltcola
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On Linux often the balance of the RAM will be "absorbed" by cache, though it is technically free.

Look at the output of "free"

The memory in the -/+ buffers/cache line under "free" column is technically free.

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by:cdukes
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@stefanx
Understand that it's not a waste - but I have the VMware ESX team asking me why my server is taking up 4G of ram :-)

@mrjoltcola
So by "technically free" you mean there's 3448584 free? (as noted in the output below)
# free

             total       used       free     shared    buffers     cached

Mem:       3873336    3739956     133380          0      16248    3298956

-/+ buffers/cache:     424752    3448584

Swap:      2610520      18544    2591976

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by:mrjoltcola
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Correct. And you can run some experiments by starting up some process and watching the cache "free" shrink.
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by:cdukes
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Oddly...if I log into webmin, it shows mem usage at:
3.69 GB total, 488.22 MB used
This is weird...?
If I look at the vmware esx server it shows memory usage at 3.2g
Is there anything I can do to make the vmware team feel better?
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by:mrjoltcola
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>>Is there anything I can do to make the vmware team feel better?

I don't know. Educate them on Linux? Why are they worried, is there some sort of system performance problem?
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by:cdukes
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Yeah...good point. I've supplied them with my findings, thanks for your help!
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by:stefanx
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Mybe your VMWare team should just assign you less memory?
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