free -m Output can it be incorrect ?

Alexrkkl · 03-20-2012, 10:01 AM

Hi there, what I want to know is the free -m output, can that be wrong? Can it display the incorrect amount of memory installed in the machine?

I issue the command and the out put is this:

Quote:

total used free shared buffers cached
Mem: 3823 3717 106 0 4 2596
-/+ buffers/cache: 1116 2706
Swap: 6015 127 5888

This suggests to me there's only 3 GB RAM installed in this linux machine, the person who looks after the server in the data centre seems to think there should be 8GB RAM installed in those machines is there any reason that this output could be wrong?

Also on one of our other linux servers the out put is this:

Quote:

total used free shared buffers cached
Mem: 16105 15666 438 0 60 12584
-/+ buffers/cache: 3022 13083
Swap: 5023 0 5023

Suggesting that there's 16GB RAM installed in this server but the guy said there's only 4GB installed in that server.

Thanks in advanced

suicidaleggroll · 03-20-2012, 10:05 AM

Typo in the second free -m output? Looks the same as the first.

What OS and architecture are running on the first machine? I've never seen an error with free in my machines.

1GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:          1001        973         27          0         44         44
-/+ buffers/cache:        884        117
Swap:         1992        531       1460

8GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:          7969       7850        119          0       2663         93
-/+ buffers/cache:       5093       2876
Swap:        18433         22      18411

72GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:         72633      67989       4643          0        124      53850
-/+ buffers/cache:      14014      58618
Swap:          999          0        999

Alexrkkl · 03-20-2012, 10:14 AM

Yeah sorry mate I copied the same output in both on the first machine running RHEL 6 and the second one is RHEL 5

Quote:

Originally Posted by suicidaleggroll

Typo in the second free -m output? Looks the same as the first.

What OS and architecture are running on the first machine? I've never seen an error with free in my machines.

1GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:          1001        973         27          0         44         44
-/+ buffers/cache:        884        117
Swap:         1992        531       1460

8GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:          7969       7850        119          0       2663         93
-/+ buffers/cache:       5093       2876
Swap:        18433         22      18411

72GB machine:

Code:

             total       used       free     shared    buffers     cached
Mem:         72633      67989       4643          0        124      53850
-/+ buffers/cache:      14014      58618
Swap:          999          0        999

suicidaleggroll · 03-20-2012, 10:52 AM

Looks to me like the person who is telling you how much ram is in each machine is mistaken. What does "top" say that the total memory is? If you reboot the machine and enter the BIOS, what does that say?

By "architecture" I meant 32/64 bit

Alexrkkl · 03-20-2012, 11:06 AM

I thought they were mistaken also ! the out put is the same as free -m

Code:

Mem:   3915556k total,  3656492k used,   259064k free,   179108k buffers
Swap:  6160376k total,      160k used,  6160216k free,  2932728k cached

We can't reboot the machine and enter the BIOS today as the machine isn't on site its in a data centre.

Also its 64 bit.

Quote:

Originally Posted by suicidaleggroll

Looks to me like the person who is telling you how much ram is in each machine is mistaken. What does "top" say that the total memory is? If you reboot the machine and enter the BIOS, what does that say?

By "architecture" I meant 32/64 bit

salasi · 03-20-2012, 01:18 PM

A couple of comments:

it would be more helpful not to go back to the original post and re-edit the data there...it is just very confusing for anyone who comes along later and reads the thread
the word 'installed'; I checked the free man page, and it doesn't mentioned the word installed. It says the amount of memory in the machine. Now, you may thing that this is nitpicking, but you can plug in memory that is not visible to the operating system, and, if you do that, free will (correctly) report the amount visible to the OS and not the amount plugged in.

I think that the first case that you mention (the 3G/8G machine, in case you edit it) may well be a case of a machine with 8G physically plugged in, but less seen, due to a 32 bit (non-PAE!) OS or a BIOS issue. The second (16G/4G) seems more like a straight mistake. If everything is running fine, and there are no performance issues because of these uncertainties, I don't think that I'd be messing with it.

grim76 · 03-20-2012, 02:19 PM

Some newer servers are coming with options to keep banks of RAM as spares and mirrors. You might have them check to make sure in the bios that those options are configured correctly as well. It is a long shot that this would be the problem, but have seen it on a couple machines.