From free -m, I see that the machine has 377 MB of used memory and 1649 MB for free (of which 1567 ubuntu is cached). See below the actual output:
caz@riskvm:~$ free -m
total used free shared buffers cached
Mem: 2026 1975 51 0 30 1567
-/+ buffers/cache: 377 1649
Swap: 3153 87 3065
However, when I look at the top output, I see processes using 1GB and 273MB in the RES column. RES means that it is in raw physical memory from a top-level page.
top - 11:45:26 up 1 day, 38 min, 3 users, load average: 0.27, 0.21, 0.23
Tasks: 125 total, 1 running, 123 sleeping, 0 stopped, 1 zombie
Cpu(s): 0.2%us, 6.6%sy, 0.0%ni, 92.8%id, 0.5%wa, 0.0%hi, 0.0%si, 0.0%st
Mem: 2075560k total, 2023796k used, 51764k free, 31264k buffers
Swap: 3229024k total, 89764k used, 3139260k free, 1605400k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
6689 root 20 0 1242m 1.0g 1.0g S 13 51.1 292:59.21 vmware-vmx
6658 root 20 0 492m 273m 262m S 2 13.5 41:16.75 vmware-vmx
1 root 20 0 2844 536 484 S 0 0.0 0:01.50 init
2 root 15 -5 0 0 0 S 0 0.0 0:00.00 kthreadd
3 root RT -5 0 0 0 S 0 0.0 0:00.02 migration/0
I understand that some of them are shared by other processes (shared objects, etc.). But if there is 1 GB of memory shared by other processes, surely at least it should be used?
How does the free report on 377 MB of memory work, and when I look from above, I see processes using 1 GB or more of RES memory?