Multi-core rendering issue. It stops using most of my cores near end?

Started by pixelsmack, July 08, 2021, 01:37:13 pm

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Why does it do this? You can see it still is using many buckets but CPU usage falls off a cliff when the render gets to around 95% complete. If the CPU usage maintained the same amount consistently, the render would've been done in around 24-minutes. Because of the CPU fall-off, it's looking to complete at around 35-minutes. Maybe even 40-minutes! That's nearly the entire render time for the first 95% for the last 5%!

Yes, I have tried various bucket settings. None seem to alter this behavior.


Well, as you can see, only 4 buckets are working. Buckets are assigned one core/thread. They don't get assigned more cores. So only 4 cores/threads can be working on the render right now until it finishes. Which yes, does slow down the render. It would be nice if TG could cache a partial bucket, and then split that bucket up between idle cores, but that isn't functionality TG has right now. I think when that's possible, we'll also be able to suspend renders to cache files too, which would also be nice.


I see. Thank you for the reply. 

One thing that has helped, a little, tile rendering even "normal sized" renders. So a 1080p or 2160p render, breaking it in to 4 tiles or even 8, helps with the efficiency. So when it hits this CPU Cliff, it's spread out and the affect isn't as heavy.