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Nice idea, but something has gone very wrong here: >Sequential throughput: ~1.3 GB/s [on a RTX 3070 Laptop] This RTX 3070 chip is on PCIe 4.0 x16 which should give 64GB/s. The 8GB of GDDR6 is 448GB/s. Swapping to an NVMe drive would be twice as fast, but with higher latency.
Swapping to a NVMe will also consume PE cycles on your NAND, ie wearing it out over time. RAM/VRAM don’t degrade from use.
Does anyone these days really use swap for anything than S4 suspend ?
https://news.ycombinator.com/item?id=40697318 This HN comment and the linked post brought up a lot of good points. The main takeaway is that swap should primarily be considered a mechanism for equality of reclamation, not for emergency extra memory, where equality of reclamation means file-backed pages and anonymous pages are subject to similar criteria for being evicted from physical memory. I used to have zero swap…
I don't consider swap to be emergency RAM storage. I know that the kernel will decide by itself to use swap even if it has plenty of available RAM and the swappiness threshold is not reached.
Nevertheless, my two decent laptops (one with 16 GB RAM, the other with 64 GB RAM) never swap, even with Docker Swarm and multiple stacks, multiple VMs, desktop activities, and gaming.
It's been a while since I last saw a physical machine actively swapping.
I understand that some limited hardware may need swap, but I can't see such hardware having a GPU with plenty of VRAM.
That said, hacking things is always fun :)
For windows I saw something similar to this years ago. An experimental proof of concept driver that allows the creation of a ram drive from vram for NVIDIA cards. Sequential is fast as you'd expect, random has lots of room for improvement. >GpuRamDrive >Create a virtual drive backed by GPU RAM. https://github.com/prsyahmi/GpuRamDrive Fork with AMD support: https://github.com/brzz/GpuRamDrive/
Similar but using OpenCL APIs, so it works on AMD (for some definition of "works" since their drivers are quite buggy): https://libguestfs.org/nbdkit-vram-plugin.1.html
Remember how 16GBs used to be an enterprise level database mainframe? Well, GPUs also have stupid amounts of compute on them. I have to imagine that there is some kind of database format that's useful with GPU compute attached. Since the data is already in VRAM, the GPU can sort, join, or otherwise manipulate data as needed.
GPU-accelerated databases have a long history. I founded HeavyAI (previously MapD/OmniSci) in 2013, but there are or have been many other startups in this space, such as Voltron Data, Kinetica, Sqream, etc. And now you have major players like IBM, Starburst, and Microsoft (which just announced Fabric SQL on GPU today) working on their own GPU-accelerated systems. GPUs have a huge advantage in terms of compute, memory…
Nice idea, but something has gone very wrong here: >Sequential throughput: ~1.3 GB/s [on a RTX 3070 Laptop] This RTX 3070 chip is on PCIe 4.0 x16 which should give 64GB/s. The 8GB of GDDR6 is 448GB/s. Swapping to an NVMe drive would be twice as fast, but with higher latency.
Swapping to a NVMe will also consume PE cycles on your NAND, ie wearing it out over time. RAM/VRAM don’t degrade from use.
but flash endurance isn't a strong argument here. you probably have O(TB) of flash, and aren't going to produce PB of swap writes any time soon. if you do a lot of swapping to a small flash device, it'll happen sooner.
I'm typing from a quite old 4GB laptop, which swaps heavily to a 250G SATA ssd. sure, it's not great, but it also costs zero. currently 9GB of swap is used, and it's not really noticeable. if I open 20 more tabs, it can introduce pauses.
google says this drive was released in 2014, and SMART says POH is about 10 years.
SMART also says wear leveling count is 665 and total written is 165327189538 LBAs (78834 GiB, or 338 drive-writes). I'm not expecting it to die soon, though using a 4G laptop is a bit of a stunt these days...
the point is that a system that has sustained heavy swapping for years has not generates so many writes to worry much. a modern system with 10x speed and 10x capacity (and probably less RAM deficit) would have even less effect. even for QDR with it's few-hundred cycle endurance spec...
Earlier quoted context omitted.
https://news.ycombinator.com/item?id=40697318 This HN comment and the linked post brought up a lot of good points. The main takeaway is that swap should primarily be considered a mechanism for equality of reclamation, not for emergency extra memory, where equality of reclamation means file-backed pages and anonymous pages are subject to similar criteria for being evicted from physical memory. I used to have zero swap…
My point is not to say that swap should not be configured on a Linux system. On bare-metal machines, I personally always set a swap partition equal in size to the amount of RAM because I usually want to be able to put the machine into S4 (suspend to disk). I don't consider swap to be emergency RAM storage. I know that the kernel will decide by itself to use swap even if it has plenty of available RAM and the swappine…