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> Since GPU memory in the Windows Display Driver Model requires it to be backed by the host machine’s virtual memory Wow, this seems really unintuitive to me,
by bscphil 5y ago
> Since GPU memory in the Windows Display Driver Model requires it to be backed by the host machine’s virtual memory
Wow, this seems really unintuitive to me, especially on a OS that doesn't overcommit. Is it as unintuitive as it sounds, or is there a good reason for this?
- dahart 5y agoThere are good reasons, not all of which I know or understand, but my basic mental model is that the backing is required for various scenarios where virtual memory might need to get relocated, either in response to a malloc or to something else. I’m told it’s complicated by having the GPU drive the display, and by scenarios involving multiple GPUs in a system. I’m guessing the description in the WDDM docs about DDI might be relevant to what’s happening under the covers in WDDM2? I’m not sure… :) https://docs.microsoft.com/en-us/windows-hardware/drivers/display/gpu-virtual-memory-in-wddm-2-0 https://docs.microsoft.com/en-us/windows-hardware/drivers/di...
- Const-me 5y ago> is there a good reason for this? Multitasking. User can easily alt+tab into another program which also uses GPU. When many processes are using GPU concurrently, it's possible their combined VRAM use exceeds the amount of physical memory available on the GPU.