"Cannot allocate memory" while no process seems to be using up memory

I am not competent on server issues, any help is much appreciated. When try to start a python/django shell on a linux box, I am getting OSError: [Errno 12] Cannot allocate memory.

free -m seems to confirm I am out of memory:

 total used free shared buffers cached
Mem: 590 560 29 0 3 37
-/+ buffers/cache: 518 71
Swap: 0 0 0

But I cannot see what is eating up the memory with top or ps aux:

 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1 root 20 0 24336 908 0 S 0.0 0.2 0:00.68 init 2 root 20 0 0 0 0 S 0.0 0.0 0:00.00 kthreadd 3 root 20 0 0 0 0 S 0.0 0.0 0:04.85 ksoftirqd/0 

How can I identify the leak? Thanks.

BTW, I am not sure if it is relevant, but the machine I am talking about is an AWS EC2 instance with Ubuntu 12 running.

2 Answers

Try this:

1. Go into top.
2. Press F (i.e., Shift+F) to specify the sort field.
3. Type N.  This will turn the lowercase n in the list into an uppercase N.
4. Press Enter.  The list should now be sorted by memory usage.

Press ? or h at the main screen for more options.

 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1010 mysql 20 0 545m 37m 1412 S 0.0 6.3 0:32.97 mysqld 939 bind 20 0 157m 11m 1896 S 0.0 1.9 0:00.03 named 3036 ubuntu 20 0 25260 7812 1720 S 0.0 1.3 0:00.42 bash 1212 root 20 0 192m 7420 2680 S 0.0 1.2 0:03.87 apache2 1322 www-data 20 0 192m 5880 1088 S 0.0 1.0 0:00.00 apache2 1323 www-data 20 0 192m 5188 436 S 0.0 0.9 0:00.00 apache2 1325 www-data 20 0 192m 5188 436 S 0.0 0.9 0:00.00 apache2 1328 www-data 20 0 192m 5188 436 S 0.0 0.9 0:00.00 apache2 1329 www-data 20 0 192m 5188 436 S 0.0 0.9 0:00.00 apache2 968 whoopsie 20 0 197m 4332 2980 S 0.0 0.7 0:00.01 whoopsie 795 root 20 0 153m 4256 3036 S 0.0 0.7 0:00.06 NetworkManager 2919 root 20 0 90156 3964 3064 S 0.0 0.7 0:00.02 sshd 804 root 20 0 101m 3656 2656 S 0.0 0.6 0:00.03 cupsd 1498 root 20 0 570m 3396 2312 S 0.0 0.6 0:00.03 console-kit-dae 693 root 20 0 49948 2876 2272 S 0.0 0.5 0:00.01 sshd 756 root 20 0 79036 2844 2044 S 0.0 0.5 0:00.02 modem-manager 964 root 20 0 124m 2844 2348 S 0.0 0.5 0:00.02 gdm-binary

ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS

will also sort all processes by memory usage descending.