Runner: built-in hybrid GPU+CPU rendering option (replace blender wrapper) #33

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opened 2026-10-29 11:10:27 +00:00 by jerry · 2 comments

jerry commented

2026-10-29 11:10:27 +00:00

Contributor

Problem

The runner can only render GPU-only (HIP/CUDA/OptiX) or CPU-only (--force-cpu-rendering). Its enable_gpu.py turns on GPU devices only, so Cycles hybrid (GPU + CPU together) is impossible without hacks.

On ai1 (Ryzen AI Max+ 395, Radeon iGPU, HIP-RT) we currently get hybrid by symlinking /usr/local/bin/blender to a wrapper that injects -P hybrid-devices.py before -f/-a. It works, but it lives outside jiggablend and outside ansible, and any runner update could break it.

Evidence it is worth it

A/B test on 2026-10-28, frames 542/544/540 of a 2560x1440, 4096spp scene, Blender 5.2.3, HIP-RT on:

GPU-only: avg 496.3 s/frame, peak device mem 13387 MiB, ~62 W package
GPU+CPU: avg 398.4 s/frame, peak 10160 MiB, ~122 W package (max 160 W)
19.7% faster (run-to-run spread about 3 s), about 26 h saved on a 1308-frame job. No faults. It has run clean as job 3 since then.

Ask

Add a runner option (flag and/or env, e.g. --hybrid-rendering / JIGGABLEND_HYBRID=1, default off) that, when a GPU compute type is selected, also sets use=True on the CPU device in enable_gpu.py.

Log the enabled devices in the task log.
Ignored when --force-cpu-rendering is set or no GPU is found.
Optional: report it to the manager so the job or runner view shows hybrid vs GPU-only.

Done when

The flag renders with both devices listed in the task log, and with it off nothing changes.
The release notes document it. After that, ops drops the ai1 wrapper and sets the flag through ansible.

Reference: the current wrapper is /usr/local/lib/jiggablend/blender-hybrid plus hybrid-devices.py on ai1.

## Problem The runner can only render GPU-only (HIP/CUDA/OptiX) or CPU-only (`--force-cpu-rendering`). Its `enable_gpu.py` turns on GPU devices only, so Cycles hybrid (GPU + CPU together) is impossible without hacks. On ai1 (Ryzen AI Max+ 395, Radeon iGPU, HIP-RT) we currently get hybrid by symlinking `/usr/local/bin/blender` to a wrapper that injects `-P hybrid-devices.py` before `-f/-a`. It works, but it lives outside jiggablend and outside ansible, and any runner update could break it. ## Evidence it is worth it A/B test on 2026-10-28, frames 542/544/540 of a 2560x1440, 4096spp scene, Blender 5.2.3, HIP-RT on: - GPU-only: avg 496.3 s/frame, peak device mem 13387 MiB, ~62 W package - GPU+CPU: avg 398.4 s/frame, peak 10160 MiB, ~122 W package (max 160 W) - 19.7% faster (run-to-run spread about 3 s), about 26 h saved on a 1308-frame job. No faults. It has run clean as job 3 since then. ## Ask Add a runner option (flag and/or env, e.g. `--hybrid-rendering` / `JIGGABLEND_HYBRID=1`, default off) that, when a GPU compute type is selected, also sets `use=True` on the CPU device in `enable_gpu.py`. - Log the enabled devices in the task log. - Ignored when `--force-cpu-rendering` is set or no GPU is found. - Optional: report it to the manager so the job or runner view shows hybrid vs GPU-only. ## Done when - The flag renders with both devices listed in the task log, and with it off nothing changes. - The release notes document it. After that, ops drops the ai1 wrapper and sets the flag through ansible. Reference: the current wrapper is `/usr/local/lib/jiggablend/blender-hybrid` plus `hybrid-devices.py` on ai1.

ash was assigned by eva

2026-10-29 11:10:46 +00:00

eva commented

2026-10-29 11:10:56 +00:00

Owner

Triaged and assigned to Ash. The scope in the body is clear and Mira sets when it gets picked up.

Notes for the PR:

Keep the new option off by default, so a runner without it renders exactly as it does today. Show that in the PR with a before/after task log.
With it on, the task log should list every enabled device (GPU and CPU). Show one real render with both listed.
CPU-only mode and "no GPU found" should ignore the option. Cover those with tests.
Reporting hybrid vs GPU-only to the manager is optional, and fine as a follow-up issue if it grows the diff.
Document the flag or env var in the release notes. Ops removes the ai1 wrapper through ansible after the release, which is a separate ansible change for Jerry.
PR into develop. Eva reviews, Linus merges.

Triaged and assigned to Ash. The scope in the body is clear and Mira sets when it gets picked up. Notes for the PR: - Keep the new option off by default, so a runner without it renders exactly as it does today. Show that in the PR with a before/after task log. - With it on, the task log should list every enabled device (GPU and CPU). Show one real render with both listed. - CPU-only mode and "no GPU found" should ignore the option. Cover those with tests. - Reporting hybrid vs GPU-only to the manager is optional, and fine as a follow-up issue if it grows the diff. - Document the flag or env var in the release notes. Ops removes the ai1 wrapper through ansible after the release, which is a separate ansible change for Jerry. - PR into develop. Eva reviews, Linus merges.

mira commented

2026-10-29 14:18:24 +00:00

Collaborator

Ruling: ACCEPT. This is Ash's next pick, top of his queue now.

Purpose: meets #4 (runners render with the Blender setup jiggablend controls, not a hand-placed wrapper that a runner update can break), and it cuts render time about 20% on ai1, which serves meets #1.

Acceptance, in plain words (Eva's notes above stand):

With the option off, a runner renders exactly as it does today.
With it on and a GPU found, the task log lists both the GPU and the CPU, shown with one real render.
CPU-only mode or no GPU: the option is ignored, and tests cover both.
The release notes say how to turn it on.
Showing hybrid vs GPU-only in the manager is a follow-up issue, not part of this PR.

Once it's released, Jerry drops the ai1 wrapper and sets the option through ansible.

Ruling: ACCEPT. This is Ash's next pick, top of his queue now. Purpose: meets #4 (runners render with the Blender setup jiggablend controls, not a hand-placed wrapper that a runner update can break), and it cuts render time about 20% on ai1, which serves meets #1. Acceptance, in plain words (Eva's notes above stand): - With the option off, a runner renders exactly as it does today. - With it on and a GPU found, the task log lists both the GPU and the CPU, shown with one real render. - CPU-only mode or no GPU: the option is ignored, and tests cover both. - The release notes say how to turn it on. - Showing hybrid vs GPU-only in the manager is a follow-up issue, not part of this PR. Once it's released, Jerry drops the ai1 wrapper and sets the option through ansible.

ash referenced this issue from a commit

2026-10-29 14:57:25 +00:00

runner: add --hybrid-rendering to render Cycles on CPU and GPU together (closes #33)

ash referenced this issue from a pull request that will close it,

2026-10-29 14:57:38 +00:00

runner: add --hybrid-rendering to render Cycles on CPU and GPU together #34