I've found that putting swap files on things that don't behave like filesystems can cause interesting behaviors. In this case, all writes to the file would go through the VFS. I imagine there could be some curious issues if that write path has any allocations or significant amount of mutation in it.
I would trust more something that got rid of the VFS layer and simply allowed VRAM to be used directly as a second level below RAM using the transcendental memory model.
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It's already possible on Linux. You can use SWAP file instead of partition and there also SWAP priorities available.
I've found that putting swap files on things that don't behave like filesystems can cause interesting behaviors. In this case, all writes to the file would go through the VFS. I imagine there could be some curious issues if that write path has any allocations or significant amount of mutation in it.
I would trust more something that got rid of the VFS layer and simply allowed VRAM to be used directly as a second level below RAM using the transcendental memory model.
And even some otherwise fairly ordinary filesystems don't support swap files (e.g. btrfs).