How can I free my GPU memory in Ubuntu 14.04?

How can I free my gpu memory as much as possible?
Currently there seems 400+ MB of GPU ram to be always occupied!
How can I free these ?

Wed Feb 24 21:48:33 2016       
+------------------------------------------------------+                       
| NVIDIA-SMI 352.39     Driver Version: 352.39         |                       
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  GeForce GTX 750     Off  | 0000:01:00.0      On |                  N/A |
| 22%   31C    P8     0W /  38W |    438MiB /  2046MiB |      2%      Default |
+-------------------------------+----------------------+----------------------+

+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID  Type  Process name                               Usage      |
|=============================================================================|
|    0       731    C   /usr/bin/python                                 24MiB |
|    0      1121    G   /usr/bin/X                                     260MiB |
|    0      2058    G   compiz                                         140MiB |
|    0      8408    G   /proc/self/exe                                   3MiB |
+-----------------------------------------------------------------------------+

Solution 1:

  1. Check what is using your GPU memory with sudo fuser -v /dev/nvidia*

The output will be as follows:

                     USER       PID   ACCESS  COMMAND
/dev/nvidia0:        root       10    F...m   Xorg
                     user       1025  F...m   compiz
                     user       1070  F...m   python
                     user       2001  F...m   python
  1. kill the PID that you no longer need with sudo kill -9 <PID>
    Example: sudo kill -9 2001

Solution 2:

nvidia-smi

NVIDIA System Management Interface program

sudo nvidia-smi --gpu-reset -i 0