alt Hacker NewsThis is my post. Basically, I needed P2P between four R9700s for tensor parallel serving, which means a 32 GB BAR on each card. With all six GPUs in, the BIOS couldn't map them, and Linux sized the switch's window too small, so only two cards got their BARs. The module in the post works around that. With P2P off, prefill was about half as fast.
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Interesting. This sort of thing is highly bios specific, I'm running 240G of VRAM on a single box using a very simple config:
GRUB_CMDLINE_LINUX_DEFAULT="pcie_aspm=off amd_iommu=on iommu=pt pci=realloc,firmware noapic nomodeset pci=nommconf gpu_unlock.targets=0000:66:00.0,0000:69:00.0,0000:6d:00.0,0000:6e:00.0"
The gpu_unlock is a bit hacky (but I have many GPUs that the unlock won't work on and that will cause issues), and there are two BIOS settings that matter: above 4GB decode enabled and resizeable bar enabled. That's it.
sidebar: Why don't your posts include pics of your rig?
Asking because I really want to see your kit.
Odd. I'm using 7 GPUs (8 if you include the onboard AST2500) and haven't had this issue, but these are directly connected to the mainboard
I did disable CSM which used base memory resources needed by REBAR, but aside from that I've 6x Tesla P4s, 1x 750TI, and the AST2500 all happily working together.
My board is a Cloud Star C612 (6x DDR4 variant), 2 PCIE ports bifurcated (so 4 GPUs in total, the others sit on dedicated ports), with a Xeon E5 2696v3 and TBU.