This is an oversight of #122543, for which benchmarking was done in
the headless mode.
The solution is to tweak policy a little bit, and keep refresh intervals
low for the first 10 seconds of render, after which increase updates to
every 15 seconds. Doing so allows:
- Have quick cancel of complex files when the error is noticed during
the first few samples.
- Have more predictable cancel time after long render.
- Mitigate the performance regression.
This does not fully solve the regression, but it makes it much more
manageable. There are some compromises to be done from the performance
for the UI renders. The interactivity is also not as fantastic, but it
could be solved later by introducing some "Instant Cancel" operations
which would be able to also stop render in the middle of a sample.
Performance measured with the Spring file (path tracing time in seconds):
Samples: 300 1024 2048
Base (prior to #122543): 29.1 85.4 174.1
This patch: 37.0 95.7 180.2
This is measured on M2 Ultra GPU render.
The penalty is close to a constant time (the time within which a more
interactive cancel is possible.
Pull Request: https://projects.blender.org/blender/blender/pulls/122658
6e0a49265a