Handle psutil.virtual_memory failures on macOS

[yuuki84573]

Summary

This PR prevents ComfyUI from crashing when psutil.virtual_memory() raises a RuntimeError.

On macOS 27 beta 2, psutil.virtual_memory() can fail with:

RuntimeError: host_statistics64(HOST_VM_INFO64) syscall failed: (ipc/mig) array not large enough

This was reported in #14498.
The crash happens during prompt execution when ComfyUI checks available system memory. This PR wraps ComfyUI's psutil.virtual_memory() usage and falls back to safe/default memory values when that call fails, allowing execution to continue instead of crashing the prompt worker thread.

Fixes #14498

Changes

• Added a small helper around psutil.virtual_memory().
• Replaced direct memory-stat calls in execution and memory-management paths.
• Logs a warning once when fallback memory values are used.
• Preserves existing behavior when psutil.virtual_memory() works normally.

Testing

• Reproduced the issue on macOS 27 beta 2.
• Verified ComfyUI no longer crashes during prompt execution.
• Confirmed the fallback path is used and logs:

psutil.virtual_memory() failed; using fallback memory values

• Ran Python syntax checks on the modified files.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 13ef3b71-fdad-4c02-ba84-c955545c8048

📥 Commits

Reviewing files that changed from the base of the PR and between dd17deb and 67d6cca.

📒 Files selected for processing (4)

• comfy/model_management.py
• comfy/psutil_utils.py
• comfy_execution/caching.py
• execution.py

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📝 Walkthrough

Walkthrough

Changes

A new module, comfy/psutil_utils.py, is added to wrap psutil.virtual_memory() calls with a fallback mechanism that handles RuntimeError by computing an approximate total via os.sysconf and logging a one-time warning. comfy/model_management.py, comfy_execution/caching.py, and execution.py are updated to remove direct psutil imports and route their system RAM total/available queries through the new comfy.psutil_utils helpers (virtual_memory_total, virtual_memory_available), including RAM pressure and pin budget calculations.

Sequence Diagram(s)

Included in the hidden review stack artifact above.

Related Issues: None specified in the provided information.

Related PRs: None specified in the provided information.

Suggested labels: memory-management, refactor

Suggested reviewers: comfyanonymous

Poem: A rabbit hopped through psutil's den, found RuntimeErrors now and then. Built a fallback, snug and neat, so memory checks won't skip a beat. Hop, hop, hooray, the RAM's okay!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly matches the PR's main change: adding fallback handling for psutil.virtual_memory failures on macOS.
Description check	✅ Passed	The description is directly about the crash fix and fallback memory handling introduced by this PR.
Linked Issues check	✅ Passed	The changes add fallback-aware memory checks in the execution and RAM-management paths, which addresses the crash and free-memory detection goals in #14498.
Out of Scope Changes check	✅ Passed	The PR stays focused on psutil fallback handling and related memory-check call sites, with no obvious unrelated changes.

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