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Excessive CPU load and slow animation playback
Confirmed, NormalPublicBUG


System Information
Operating system: Win 10 1909
CPU: Threadripper 3990X
RAM: 128GB
Graphics card: RTX 2080 TI

Blender Version
Broken: 2.93A, 2.92, 2.91
Worked: 2.83 LTS all versions

Short description of error
Playing back the animation results in an excessive CPU load and very low FPS in all 2.9X versions of blender.
Even removing all meshes from the scene and having just the armature results in an extreme CPU load with very slow playback.
This issue is not present in 2.83.

Below are some screenshots I took with the tree creature file, as well as a human rig.
as you can see the CPU load is around 4% with the human rig in 2.83 and 54FPS. when opening the same in 2.9X, the CPU load is 80% with 42FPS.
This is with no keyframes set, when using a scene that has keyframes, the difference is much greater. 48FPS in 2.83 vs 11FPS in 2.9x.

Exact steps for others to reproduce the error

  • Load any character with an animated armature
  • hit space to play and look at frame rate and CPU load.

Event Timeline

steven (steven850) updated the task description. (Show Details)

I can see an increase in CPU usage from 26% to 33% with the tree creature file.
However, the FPS remained the same (around 12 fps in my case).

**System Information**
Operating system: Windows-10-10.0.19041-SP0 64 Bits
Graphics card: Radeon (TM) RX 480 Graphics ATI Technologies Inc. 4.5.14760 Core Profile Context 27.20.14537.1001

The apparent regression occurred at some point between 826f6dd9ee20 (Apr 23) and fdebdfa320ec (May 4)

What CPU did you test that with? I can go to single numa node, and disable cores to match yours to see if I get the same numbers.

Germano Cavalcante (mano-wii) changed the task status from Needs Triage to Confirmed.Mar 18 2021, 10:31 PM
Germano Cavalcante (mano-wii) changed the subtype of this task from "Report" to "Bug".

My CPU is an AMD Ryzen 7 1800x
The increase in CPU usage was caused by rBd8a3f3595af0: Task: Use TBB as Task Scheduler.

I don’t know if it’s a known effect in favor of something, but I believe it deserves an investigation, so I am confirming it as a bug for now.

To clarify, on the tree creature file I obviously have all objects except the creature hidden, and subsurf turned off.

I disabled some cores and went to 8 to match your CPU and these are the results I got.
CPU load goes from 39 to 65%

Increased to 32 cores, single numa node and got the following
Still seeing a doubling of the cpu load, but also a decrease in FPS as core count increases.

8 cores = 25 fps
32 cores= 21 fps
64cores= 18 fps

seeing the same results with the human rig. As Core count increases CPU load increases and FPS drops. With 8 cores I was actually getting 60FPS.

To clarify, on the tree creature file I obviously have all objects except the creature hidden, and subsurf turned off.

In that case it would be good to attach a simplified file where the problem is more evident.

I tested it with a different number of threads,
I noticed a bigger difference between 8 and 16 threads.