The reason this is difficult is because each render bucket/thread has its own cache at present. We have no mechanism for splitting a cache or sharing it, so we can't dynamically subdivide buckets. Matt has thoughts on the future for improving efficiency and this is the kind of thing he is certainly keeping in mind, but I can't say we have a specific solution for this issue coming in the near future. Fortunately in most scenes it does not make a massive difference. If you're seeing 10 minute render times to complete a single, final tile, I wonder what your overall frame render times are...
- Oshyan