1. Introduction §

Hi, did you ever wonder if you could use your GPU memory as a mount point, like one does with tmpfs and RAM?

Well, there is a project named vramfs that allows you to do exactly this on FUSE compatible operating system.

In this test, I used an NVIDIA GTX 1060 6GB in an external GPU case connected with a thunderbolt cable to a Lenovo T470 laptop running Gentoo.

vramfs official GitHub project page

2. Setup §

Install the dependencies, you need a C++ compiler and OpenCL headers for C++ (the package name usually contains "clhpp").

Download the sources, either with git or using an archive.

Run make and you should obtain a binary in bin/vramfs.

3. Usage §

It's pretty straightforward to use, as root, run vramfs /mountpoint 3G to mount a 3 GB storage on /mountpoint.

The program will stay in foreground, use Ctrl+C to unmount and stop the mount point.

4. Speed test §

I've been doing a simple speed test using dd to measure the write speed compare to a tmpfs.

The vramfs mount point was able to achieve 971 MB/s, it was CPU bound by the FUSE program because FUSE isn't very efficient compared to a kernel module handling a file system.

t470 /mnt/vram # env LC_ALL=C dd if=/dev/zero of=here.disk bs=64k count=30000
30000+0 records in
30000+0 records out
1966080000 bytes (2.0 GB, 1.8 GiB) copied, 2.02388 s, 971 MB/s

Meanwhile, the good old tmpfs reached 3.2 GB/s without using much CPU, this is a clear winner.

t470 /mnt/tmpfs # env LC_ALL=C dd if=/dev/zero of=here.disk bs=64k count=30000
30000+0 records in
30000+0 records out
1966080000 bytes (2.0 GB, 1.8 GiB) copied, 0.611312 s, 3.2 GB/s

5. Limitations §

I tried to use the vram mount point as a temporary directory for portage (the Gentoo tool building packages), but it didn't work due to an error. After this error, I had to umount and recreate the mount point otherwise I was left with an irremovable directory. There are bugs in vramfs, no doubts here :-)

Arch Linux wiki has a guide explaining how to use vramfs to store a swap file, but it seems to be risky for the system stability.

ArchWiki: Swap on video

6. Conclusion §

It's pretty cool to know that on Linux you can do almost what you want, even store data in your GPU memory.

However, I'm still trying to figure a real use case for vramfs except that it's pretty cool and impressive. If you figure a useful situation, please let me know.