Does my RPi uses video RAM for tunneling X over ssh?

Question

I use my Pi in headless mode, and I like to use X over SSH occasionally to run graphics only apps like the Pi store, and a few of my programs. I'd like to increase my RAM by decreasing GPU RAM, in accordance to the answer of this question.

For example, this is how I would start the session: ssh -X pi@[IP ADDRESS]. I can then run startxfce4 and it'll start the GUI in X11 on my Mac, resulting in a VNC-style connection.

In doing so, I'm running the X server on my Mac, so does that mean that no video RAM is being used on the RPi because my Mac is the one handling the Graphics?

Answer 1

I don't know why it should.

You run the X-server on your Mac. And the Pi only runs X-clients, that talk X-protocol tunnelled through SSH with the server on your Mac, which does all the drawing.

Since you won't be using a lot of GPU RAM, you can set the split with raspi-config, to a smaller value. That way you have a bit more RAM available for your programs to use.

Answer 2

The very minimum you can allocate to the GPU is 16MB. To do so edit the file /boot/config.txt:

Setting:

gpu_mem=16

(edit: a reboot is required for this change to take effect). This is required to load the GPU firmware, not just the framebuffer. See http://elinux.org/RPiconfig for more info.

If you want to reduce memory use consider using dropbear rather than OpenSSH (saves ~10MB), dash over bash (~1MB), remove unsed ttys (~3MB), you can go further:

Raspberry Pi Raspbian tuning / optimising / optimizing for reduced memory usage ( dropbear + getty + no ipv6 + dash + swap + noop + overclock + syslogd )