Add --mmap-torch-files to enable use of mmap when loading ckpt/pt

[comfyanonymous]

No description provided.

[richardm1]

I'm thoroughly confused. We've been going around and around in an effort to gain the ability to disable memory mapped checkpoint reads -- there's every indication the Stable Diffusion ecosystem (including Comfy) loads via mmap by default and this wreaks havoc on anyone not using local NVMe storage storage due to the choppy, small block, discontiguous I/O. This pull turns on something that's already on?

I've tried this switch and it doesn't help. What does help is this hack.

I'm digging around for some strace or bpftrace that can confirm/refute the notion of mmap reads by default...

[mcmonkey4eva]

@richardm1 it's the safetensors lib that mmaps by default, this PR is specifically for legacy ckpt files (which still get used for some obscure cases, eg upscale models, yolo, etc. often have pickle files).

For dealing with the mmap mess, you'll want to look at the upstream https://github.com/huggingface/safetensors