错误提示：

Failed to create model quickly; will retry using slow method.

来自国外论坛的Dragonfly275博主说明：

SOLVED

It was the SWAP-File.

My 32GB RAM had a 8GB SWAP, and during loading of the Model the used RAM went near 22GB and the error came.

I changed the SWAP to 32GB, loading the Model is making a spike in used RAM to 29GB and everything works.

The suggested --medvram
I removed it when i upgraded from RTX2060-6GB to RTX4080-12GB (both Laptop/Mobile).

The SDXL works without it.

First Impression / Test

Making images with SDXL with the same Settings (size/steps/Sampler, no highres.fix) is about 14% slower than 1.5 Models.

Using highres.fix(R-Esr) on SDXL (1024x1536->2048x3072) is taking 4,5 Minutes per image.

I noticed that with just a few more Steps the SDXL images are nearly the same quality as 1.5 images with upscale.

So:
1.5 - 4 image Batch, 16Steps, 512x768->1024x1536 - 52 sec
XL - 4 image Batch, 24Steps, 1024x1536 - 1,5 min

I hope with poper implementation of the refiner things get better, and not just more slower.

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以上回复是windows PC机，总体应该是因为显存不足造成。

对于MAC电脑，尚未遇到同类问题。