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Prerender phase memory consumption twice as big compared to 2.79 with subdiv modifier
Open, Needs Triage by DeveloperPublic

Description

System Information
Operating system: Linux-3.10.0-957.10.1.el7.x86_64-x86_64-with-centos-7.6.1810-Core 64 Bits
Graphics card: GeForce GTX 1070/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 418.56

Blender Version
Broken: version: 2.81 (sub 13), branch: master, commit date: 2019-10-04 13:28, hash: rBd590db83705b
Worked: 2.79 latest

Short description of error
This problem is noticeable on big scenes.
I have a huge city scene from alembic of 1Gb size. Blender 2.79 consumes about 30gigs peak on rendering (on caching and bvh building), while 2.81 eats up all 64Gb + 20Gb of swap and closes.
I shrunk the scene as much as possible, but the problem can still be seen.
Now this cut down scene consumes 3.2 Gb in 2.79 and 6.2Gb in 2.81.
All meshes have one subdivision modifier enabled.

I don't know what kind of magic Renderman uses, but it consumes only 3Gb on the whole scene (that one, which eats up all of my RAM in 2.81) with subdivs.
Adaptive subdivision in Blender makes it a lot worse than static subdiv even with 8 pixels dice rate.

Exact steps for others to reproduce the error
Open each file, hit render and compare the memory consumption.

Can't attach because of the size. Here are the links to download:
https://drive.google.com/open?id=1MVUfe2yqmxzkNNt6XroVAgs7x774RvOo
https://drive.google.com/open?id=1O9gPOTM1mviNcx1FaSw2aRGRYIRRQYtF

Details

Type
Bug