Port of the same change made on the v0.20.1 line, reapplied here because the
package layout moved under _internal/ in the meantime.
The mandatory Qwen stack was configured to offload to disk unconditionally.
DiffSynth implements that by dropping the weights to the meta device and
re-reading every parameter through its DiskMap on the next onload, and the
pipeline moves between text encoder, transformer and VAE on every pass, so
each generation paid a full model reload. That is the right trade on a
consumer card, where it is what makes a 20B model runnable at all, and pure
waste on a card that can simply hold the stack.
Residency is now resolved from total VRAM, mirroring how the optional
Z-Image face stack is already gated. Above the floor the config passes no
"disk" value anywhere, which is what actually disables the behavior:
DiffSynth latches disk_offload once from offload_dtype, so pointing every
device at CUDA while leaving the sentinel would keep both the meta-drop and
the re-read.
Measured on an H100: a warm global pass went from 37.3s at 0.8 GiB resident
to 2.2s at 28.7 GiB, with both stacks resident peaking at 48.0 GiB of 79.2.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>