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CPU+GPU rendering is slower than GPU-only rendering.

leyrisanleyrisan Posts: 15
in Daz Studio Discussion

I did 2 different tests on the same scene.
Ryzen 5950x CPU + 3070 GPU created 200 itreations in 1 minute 30 seconds.
I then removed the CPU option and it rendered 500 itreations in 1 minute 30 seconds with GPU only.
This gives the same result for all the scenes I've created. CPU+GPU is slower than just GPU. Okay but why?

001.png
1920 x 1080 - 4M

Comments

  • Richard HaseltineRichard Haseltine Posts: 100,807

    Yes, this is a comon experience - when the CPU is working on the render itself it has fewer resources available for managing the render, and as a result the whole process can slow down.

  • leyrisanleyrisan Posts: 15

    Incredible, but what is the solution?
    Frankly, you have to work for 4 months with minimum wage in order to have 5950x in my country.

    Therefore, I would like to use my processor in the most efficient way.

  • PerttiAPerttiA Posts: 10,024

    The most efficient way is not to use it for rendering, it is so much slower (20+ times slower) than the GPU that it's slowing down the process.

  • prixatprixat Posts: 1,588

    Do you know how much each device contributed?

    It does vary on the contents of the scene and the faster the GPU, the worse this effect becomes.

    Your's does sound particularly bad. Most of the time doing all these iterations in parallel makes up for the devices running slower. (Yes the CPU is also slowed down by the 'render management'.)

  • nicsttnicstt Posts: 11,715
    edited July 2022

    leyrisan said:

    Incredible, but what is the solution?
    Frankly, you have to work for 4 months with minimum wage in order to have 5950x in my country.

    Therefore, I would like to use my processor in the most efficient way.

    Don't use both.

    A major benefit, your PC will be cooler!

    ... And aother: you will use less power!

     

    Post edited by nicstt on
  • oddboboddbob Posts: 396

    leyrisan said:

    Therefore, I would like to use my processor in the most efficient way.

    My pc renders at about the same speed whether rendering with the CPU enabled or not.

    For me the most efficient use of the CPU is just to turn off CPU rendering and let it keep the GPU busy.

    Advantages are the PC remains somewhat usable and theres less power use/heat/noise.

  • leyrisanleyrisan Posts: 15

    nicstt said:

    leyrisan said:

    Incredible, but what is the solution?
    Frankly, you have to work for 4 months with minimum wage in order to have 5950x in my country.

    Therefore, I would like to use my processor in the most efficient way.

    Don't use both.

    A major benefit, your PC will be cooler!

    ... And aother: you will use less power!

    Thanks, now I turn off the CPU option. However, in this case, I am getting an error.
    When I press the render button for the first time, it renders through the GPU. I don't like something and I press the "cancel" button, for example, I change where the eye looks and when I press the render button again, both the cpu and the gpu work together, but whereas I only chose the GPU.

  • leyrisanleyrisan Posts: 15

    oddbob said:

    leyrisan said:

    Therefore, I would like to use my processor in the most efficient way.

    My pc renders at about the same speed whether rendering with the CPU enabled or not.

    For me the most efficient use of the CPU is just to turn off CPU rendering and let it keep the GPU busy.

    Advantages are the PC remains somewhat usable and theres less power use/heat/noise.

    Thank you, I am doing so now laugh

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