# real mem vs avail mem (RAM memory gap)



## da1 (Jan 29, 2011)

Hi guys,

On a amd64 8.1-RELEASE box, I have 2x 2GB RAM sticks and the following in dmesg:


```
real memory  = 4294967296 (4096 MB)
avail memory = 3090038784 (2946 MB)
```

Reading a bit on the web, I came across this and here is the output:

```
SYSTEM MEMORY INFORMATION:
mem_wire:         586842112 (    559MB) [ 18%] Wired: disabled for paging out
mem_active:  +     33775616 (     32MB) [  1%] Active: recently referenced
mem_inactive:+   2348044288 (   2239MB) [ 75%] Inactive: recently not referenced
mem_cache:   +    103596032 (     98MB) [  3%] Cached: almost avail. for allocation
mem_free:    +     35508224 (     33MB) [  1%] Free: fully available for allocation
mem_gap_vm:  +       524288 (      0MB) [  0%] Memory gap: UNKNOWN
-------------- ------------ ----------- ------
mem_all:     =   3108290560 (   2964MB) [100%] Total real memory managed
mem_gap_sys: +     94814208 (     90MB)        Memory gap: Kernel?!
-------------- ------------ -----------
mem_phys:    =   3203104768 (   3054MB)        Total real memory available
mem_gap_hw:  +     18120704 (     17MB)        Memory gap: Segment Mappings?!
-------------- ------------ -----------
mem_hw:      =   3221225472 (   3072MB)        Total real memory installed

SYSTEM MEMORY SUMMARY:
mem_used:         734076928 (    700MB) [ 22%] Logically used memory
mem_avail:   +   2487148544 (   2371MB) [ 77%] Logically available memory
-------------- ------------ ----------- ------
mem_total:   =   3221225472 (   3072MB) [100%] Logically total memory
```

As I can see, the OS is managing only 3 out of 4GB ram (strange since it's the amd64 version of FreeBSD).

```
FreeBSD mainserver 8.1-RELEASE FreeBSD 8.1-RELEASE #0: Mon Jul 19 02:36:49 UTC 2010     root@mason.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC  amd64
```
So I have a 1GB ram gap.

So far, I was unable to clear the mystery.

The box has ZFS on it .... is it possible that ZFS "reserves" some amount of RAM ? I think this would be too much ....

Anyone ?


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## da1 (Jan 29, 2011)

Solved. Hardware issue. Somehow the video card is eating 1 GB of RAM.


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