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- Hacker News
- I'm mostly excited for the VRAM savings from apps and games which have loads of unused or super rarely used textures.
Game developers often aren't super careful with this stuff, and there could be literal gigabytes of data which isn't used at all.
- Are there any people out there doing this optimisation post-release for existing games ?by stuaxo
- I worked on a PC/PS4/Xbox One game once. I wish I remembered more details, but at some point when looking at memory usage I found a 2048x2048 (or something like that) texture for something on a character. This texture was never anywhere near occupying the full screen. It got downsized once I told one of the artists, but I wouldn't be surprised if some games are inadvertently shipping with that kind of waste.
- Great writeup, gpuvis looks particularly interesting and glad the kernel is providing tracepoints for performance events.
> Not only does the display hardware like scanned-out images to be in VRAM, it also completely skips past the GPU’s virtual memory architecture and works with physical addresses exclusively.
Well there's your problem. Only so smart your memory management can be when you have to pay the cost of doing it manually. Although presumably this only applies to a small fraction of the VRAM?
- > Although presumably this only applies to a small fraction of the VRAM?
They did mention they saw 4GiB of eviction for a single 32MiB scan out image.
So while I would call the image allocation small, it seems to cause an avalanche of evictions. Amplified by the fact that each frame has one of these images, though I expect subsequent frames might have a better chance of already fitting into evicted space.
What I don't exactly understand is: doesn't it make sense to always reserve the contiguous physical memory for this case and not allow anything else to be put in it?
by NekkoDroid - Such great work! Happens quiet regularly I hit a game just realizing seconds later I haven't shut down my local LLM yet. At least punishment will be less harsh. Lets see, maybe some games in window mode will just work fine.by Prunkton
- Wish more people understood thisby hnc3yfnu6f
- Honestly, swap thrashing on low vRAM setups has been painful forever. Glad to see Linux kernel optimizations targeting memory pressure where it actually hurts.
- This post focuses on performance, but what about crashing due to apps seeing no RAM available to allocate once VRAM is filled up?
I remember having this problem when I used an NVIDIA 750 Ti with 2 GB of memory. Just opening a few Firefox or Ghostty terminals (both are GPU accelerated) would result in those apps crashing or not being able to render their contents. Sometimes the compositor would crash or become unstable too (kwin, niri, etc.). I had to reboot every few hours. Complete system instability.
This problem only happened with Wayland, when I switched to X windows these problems went away.
Since then I switched to an AMD RX 480 (8 GB) GPU and never had an issue here with Wayland, if GPU memory gets full, system memory gets seamlessly used instead. It felt like with the NVIDIA card, it never allocated back to system memory if no VRAM was available. This was only a problem on Linux since that same NVIDIA card was fine in Windows for 10+ years with zero issues related to instability around VRAM allocation.
Tons of people reported the same issue on Linux on NVIDIA's forums for years.
I wrote a lot more details and recorded demo videos around 9 months ago here https://nickjanetakis.com/blog/gpu-memory-allocation-bugs-wi..., but since then a lot of these things have been resolved from switching over to AMD.
by nickjj - I gave myself 32GB of swap since SSDs are quite fast and the pages sent to disk seem to intelligently be rarely referenced ones. Feels amazing to run 4 VMs and 12 Claude Code instances on my mid tier hardwareby OsrsNeedsf2P
- It's got to be an edge case for Wayland to be used with a 2GB VRAM card? Targeting recent cards and letting people using older hardware install x-windows, or whatever, seems sensible.
You say (in your blog post) "Linux" didn't work well so you reverted to "Windows", but as is so often the case you buried the distro/version info. You don't seem to have been using Win11 (later you mention Win7 & Win10Pro) ... So it's cutting edge software didn't work on my 2014 system, but older software did. The Linux/Windows aspects aren't particularly relevant AFAICT.
Nvidia refused for many years to properly support Linux, whilst AMD have supported it. So no surprise if a Nvidia card didn't work well/stably but an AMD one did.
by pbhjpbhj - I have this problem with an 8gib 2080. Nvidia drivers have bugs with Wayland or Vulkan which is at least partially a memory leak.
Here’s one for example: https://forums.developer.nvidia.com/t/kwin-6-7-x-causes-mass...
Just search KWin Nvidia memory leak or Wayland Nvidia memory leak or kwin wayland Nvidia memory leak. It’s constantly issues and I remain convinced some intermixing of the two + monitors is at fault.
by vlovich123 - Your last sentence sums it all: AMD is the only serious option on Linux. Not perfect, but far better than Nvidia, thanks to their open drivers that anyone (and especially Valve) can improve.by flaburgan
- Great article. I find that I learn something every time I read a post about linux kernel work.
I guess an LRU with priority would handle VRAM for games pretty decently without going getting too application specific.
What about VRAM to Disk specifically NVME, would direct to disk be feasible for large workloads, I know it is used for streaming in assets directly via. PCIE, but i wonder how the performance would be on compute workloads running with NVME as a swap for GPU VRAM.
by kjuulh - > but i wonder how the performance would be on compute workloads running with NVME as a swap for GPU VRAM.
4x as slow in absolute best case, NVMe drives have 4 PCIe lanes usually
- I'll be the one to ask the obvious question:
What does this mean for compute workloads? Specifically, LLM inference.
Does it mean anything at all, or is this purely a games-thing?
by hypfer - If you have model layers/experts that reside in CPU RAM, it's generally better to do that part of inference on the CPU than pay the cost of shipping them over to the GPU. LLM inference is generally bottlenecked by data-movement, not compute. There may be a limited exception for prefill or perhaps decode of very wide batches, where shuffling the data around may be justified.by zozbot234
- I doubt it makes much of a difference, and you can always manually manage what data lives in the GPU when if you 100% have to overcommit. Games have a much larger and more diverse set of objects in the VRAM, and their usage is less predictable, so manual scheduling of the memory is infeasible typically.
- Well written and very informative. I am glad we have these enthusiastic people around for Linux kernel development!by Lunar5227
- I'm sure Linus will insult them into indifferenceby bcjdjsndon
- Enthusiasm seems proportional to the number of exclamation marks (28)! (:by cubefox
- Great article! I share the same hunch as the author does; when allocating memory ultimately the application itself is in the best position to inform the kernel about the desired stickiness to VRAM. The best a kernel can do is guessing.
As a side note, it strikes me how much we owe to young trans people for low level performance engineering.
by exceptione - Of course. These are the people that the industry needs who understands proper performance-level engineering.
The commits they authored in [0] match and all of what they have mentioned in the article and this is how you know the author knows exactly what they are talking about and have explained it well.
Puts all the vibe-coders, and the so-called "AI Engineers" to shame. I know that if I ask about the basic system design of amdgpu and drm (direct rendering manager) infrastructure in Linux, a small handful will be able to explain it without using AI or googling.
[0] https://gitlab.freedesktop.org/pixelcluster/kernel/-/commits...
by rvz - They'll get old soon enough.by eru
- Gosh, 7.2 literally just dropped with a bunch of awesome of performance/gaming related improvements (large folios, cache-aware scheduling, improved MGLRU reclaiming, Fair GPU Scheduler etc)... and I already can't wait for 7.3 to come out.
Meanwhile in the Windows world, users hate updates... Like I genuinely can't think of a single instance that made users exclaim, "oh boy I just can't wait for the next Patch Tuesday!".
by d3Xt3r - > Like I genuinely can't think of a single instance that made users exclaim, "oh boy I just can't wait for the next Patch Tuesday!"
Majority of Windows users are not programming enthusiasts and just don't care.
OS works. Programs continue to work. Good. Keep it that way.
by flaunf221 - Phoronix.com is my go to place for good news. It always gives me a sense of progress and makes me feel humble since so many smart people share their workby Prunkton
- Any improvements with fractional scaling? Can anyone please link to any material reg the work being done for improving fractional scaling in Linux; it would be great if it could match the rendering quality of macOS.
- Didn't we eagerly await on updates in the good old days of Windows?by toredash
- I might be in the minority here, but some of the latest Windows updates that dropped in the Insider channel are really cool, and I'm excited to see those coming to main.by timpera