In some of the complex scenes it could a very long time for Cycles
to respond to cancel request. This is because Cycles only cancels
render at a consistent state of render buffer: when all scheduled
samples are rendered.
This was caused by the render scheduler over-scheduling the number
of samples in an attempt to improve occupancy of the GPU.
This fix makes it so the scheduler only compensates for the low
occupancy if rendering can happen within a desired update time.
There is no visible difference in the benchmark scenes with this
change.
Pull Request: https://projects.blender.org/blender/blender/pulls/122543
5f11ae70ea