Really slow Undo in 2.9 especially on multiple undos

I’ve been having an issue when using Undo in the latest release of blender 2.9

In the following situations I have noticed blender becoming unresponsive for 10 to 15 seconds:

  1. Undo after selecting multiple objects
  2. Undo in a large file (70 MB above)
  3. Repeated Undos
  4. Undo while weight painting

My Specifications:
Ryzen 7 1700X
32 GB Corsair 3000 MHZ Ram
Nvidia GTX 1080TI
Crucial MX500 Sata SSD
Windows 10 Version 1903

  1. How did you manage to create a 70mb file?
  2. Did you try it on Linux?

I’m on a 24-core Threadripper, 256GB of ram, NVMe’s out the butt, and 4x RTX 2070 Supers… Even I have a hard time with undo dragging on. The problem I discovered is that undo seems to be a single-thread operation. It doesn’t matter how much ram you have, how fast your SSD’s are, or how quick your GPU’s are at calculations… The bottleneck seems to be single-thread performance.

I’m really starting to regret spending $1,300 on an AMD threadripper.

70MB is pretty small. I’m working on a project right now that’s 1.5GB.

its a full city with traffic and trees, and life.
Its low poly so 70mb, if it were high poly then god knows what the size would have been

but buying an Intel just for undo, seems kind of pointless

My city also with trees and buildings and road sings and cars and trees only 37 MB

The city i made is a lot more dense, with parks and alleys, cars, trash bins, light poles, electricity poles, electricity wires, restaurants, restaurant interiors, you get the idea

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How about trying to break the city into small parts. All in separate Blend files. And link them as instances into the big file. This will make it easier.

ill try that out, thanks for the tip!

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A 70MB file should not be an issue for a 3D program.
And it’s not a large filesize by any means, either.

Linking could be a good idea, regardless. Overall “your file is too big” should only be an issue once we hit something ridiculous in the USD Demo file size range, though.

Hey guys, So the issue is still there but I reduced it quite a lot by disabling the Crowdrender add-on i had installed. So each time I would hit undo it would sync the blender file and blender would hang till crowd render stopped syncing.
If anyone with the add-on installed is facing the same issue can try disabling it and checking if that helps. (it is installed if after each undo you get a small balloon notification at the bottom of blender saying “Local is synced” or something along those lines)