How to improve CPU usage? Tried many bucket settings.

[Nala1977]

i can confirm that there is something going on with the render cpu usage.
im rendering right now and noticed that at the start of the image my cpu is stuck at 12% usage. Its not like the last part of the image, i mean the render just started and its stuck there at 12% usage.

Stopped it and changed the bucket size to 16/24 and restarted the render,now its using 90% of cpu.

i  think its due to some nodes used.. not sure.

p.s. some clarifications, had the bucket set to 512 | 1024, and this was causing lots of issues, went back to standard 256 | 256 and now it uses all cpus as usual

another edit: nope doesnt work anymore, after some parameter changes it doesnt render with all cores at 256 | 256. had to put it at 64/64.
something is way off

[Kadri]

Have a look here what Matt says:
https://planetside.co.uk/forums/index.php/topic,28567.0.html

Curious by "stuck" what do you mean? For how long?
In my renders in the beginning the render doesn't use all the cores too.
It goes to 100% just after a while depending on the scene. But it is a reasonable time it does this.
Curious how your scene behaves.