Use your Nvidia GPU's VRAM as swap space on Linux

A developer released a tool that allows Linux users to repurpose Nvidia GPU VRAM as swap space, effectively tripling addressable memory on systems with soldered RAM. The nbd-vram daemon uses CUDA's memory copy functions to allocate VRAM and exposes it as a block device via the kernel's NBD driver, bypassing Nvidia's restricted P2P API that limits direct VRAM access to Quadro and datacenter GPUs. The solution targets laptops with non-upgradable memory, enabling an RTX 3070 laptop to expand from 16GB to 46GB of total swap capacity by combining RAM, VRAM, zram compression, and SSD overflow.

Use your NVIDIA GPU's VRAM as swap space on Linux. Built for laptops with soldered memory and no upgrade path. If you have an RTX card sitting there with 8GB of VRAM and you're getting swapped to SSD, this puts that VRAM to work. Tested on: RTX 3070 Laptop GA104M, 16 GB physical, 8 GB VRAM , driver 580.159.03, kernel 6.17, Pop OS. Allocated 7 GB for swap. End result including zram and SSD swap ~46 GB, tripled the addressable memory. Overflow order is: RAM fills, then VRAM absorbs spill fast, PCIe , then zram compresses the rest CPU , then SSD only if everything else is exhausted. A small daemon allocates VRAM via the CUDA driver API, then serves it as a block device using the NBD Network Block Device protocol over a Unix socket. The kernel's built-in nbd driver connects to it and exposes /dev/nbdX . From there it's a normal swap device. Data path: kernel swap subsystem - /dev/nbdX - nbd kernel driver - Unix socket - nbd-vram daemon - cuMemcpyHtoD/DtoH - GPU VRAM. No kernel module to write or maintain. No NVIDIA kernel symbols. Survives kernel and driver updates without rebuilding anything. The "obvious" approach is nvidia p2p get pages persistent , which pins VRAM pages in BAR1 so the CPU can access them directly via ioremap wc . Every existing project that tried this route hits the same wall: the NVIDIA driver returns EINVAL on consumer GeForce GPUs. Both the persistent and non-persistent variants, both flag values. It's gated at the RM level for Quadro/datacenter SKUs only, regardless of driver version. The other approach - directly ioremap wc the BAR1 physical address without going through the P2P API - also doesn't work. The GPU's internal page tables only have ~16 MiB of BAR1 mapped just the display framebuffer . Reads from the rest return zeros. mkswap appears to succeed, then swapon fails because the swap header isn't actually there. The NBD approach sidesteps all of this. cuMemcpyHtoD and cuMemcpyDtoH work on any CUDA GPU without any special permissions. - NVIDIA GPU with CUDA support any consumer RTX/GTX card - NVIDIA driver with libcuda.so.1 no CUDA toolkit needed - Linux kernel 3.0+ nbd module, built into most distros nbd-client package gcc , make git clone https://github.com/c0dejedi/nbd-vram cd nbd-vram sudo ./install.sh sudo systemctl start vram-swap-nbd Verify: swapon --show NAME TYPE SIZE USED PRIO /dev/nbd0 partition 7G 0B 1500 The service is enabled on install, so it comes up automatically on every boot. Edit /etc/systemd/system/vram-swap-nbd.service : Environment=VRAM SETUP SIZE MB=7168 how much VRAM to use Environment=VRAM SWAP PRIORITY=1500 swap priority higher = used first The daemon tries the requested size first and backs off in 512 MiB steps if the GPU is short on memory - so it will grab as much as it can even if the display compositor is already loaded. VRAM SETUP SIZE MB is the ceiling, not a hard requirement. After changing, run sudo systemctl daemon-reload && sudo systemctl restart vram-swap-nbd . The installer asks whether to enable power-aware management on first install. If enabled, the service automatically stops when you unplug from AC or when battery drops below a threshold , and restarts when power is restored. Manual systemctl stop is always respected and won't be overridden. To change settings after install, edit /etc/nbd-vram.conf . Changes take effect on the next poll within 60 seconds or immediately on the next AC plug/unplug event. sudo bash test-nbd.sh Allocates VRAM, connects the NBD device, does a 1 MiB write/readback check, activates swap, then prints teardown instructions. install.sh handles teardown automatically if a test instance is running. To stress the full partition after the smoke test passes: sudo bash test-fill.sh Writes the entire VRAM partition with zeros, verifies a sample read back, then auto-restores swap on exit. Measured on RTX 3070 Laptop via test-fill.sh 7 GiB sequential write, 4M blocks : - Sequential throughput: ~1.3 GB/s - Latency is lower than NVMe since the path goes through PCIe to GPU rather than storage For laptops already using zram, set VRAM swap at a higher priority so it absorbs overflow before hitting SSD. sudo bash uninstall.sh MIT - Sean Lobjoit c0dejedi