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Multi-GPU scaling For CUDA and RTX modes

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  • Multi-GPU scaling For CUDA and RTX modes

    Hardware,
    • CPU: AMD Ryzen Threadripper 39950x Pro 64-Core
    • Motherboard: Asus Pro WS WRX80E SAGE
    • System Memory: 256 GB DDR4 3600 CL18
    • GPUs: 8x RTX 3090Ti Founders Edition
    • Bandwidth: PCIe Gen 4.0, x8
    • OS: Windows 11 Pro
    • Nvidia Studio drivers 536.40
    • No monitors attached to the GPU(s)

    Testing,

    We have tested 3 scenes on this hardware using Bucket mode, the results are double checked. The scene are setup carefully to push the GPUs to 100% usage, to ensure accurate results. All tests run for at least one full minute
    Note, although V-Ray GPU officially supports maximum of 4 GPUs for rendering, we added the results for rendering with 8 GPUs.

    First Scene, Gold_Interior

    We noticed CUDA scaling of 99.61% scaling for 2 GPUs, 96.08% for 4 GPUs and 88.47% for 8 GPUs
    The noticed RTX scaling of 101.13% for 2 GPUs, 96.26% for 4 GPUs and 92.35% for 8 GPUs​

    Click image for larger version

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    Second scene, Nutcracker
    We noticed CUDA scaling of 97.41% scaling for 2 GPUs, 99.51% for 4 GPUs and 88.72% for 8 GPUs
    The noticed RTX scaling of 97.98% for 2 GPUs, 97.71% for 4 GPUs and 95.03% for 8 GPUs​

    Click image for larger version

Name:	Screenshot_2023-11-06_at_1.14.58_PM.png?ex=662f8202&is=661d0d02&hm=f9269936e53ad24a30d9b5ea3e99f24d4d51312d50e637df0fb0d9b8890ba2d7&.png
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    Third scene, Forest_001
    Note, this scene includes thousands of leaves and grass objects, and has all shading baked to textures, hence showing a big boost for RTX mode. In most cases CUDA mode should be close to RTX mode in performance.

    We noticed CUDA scaling of 99.11% scaling for 2 GPUs, 98.89% for 4 GPUs and 89.79% for 8 GPUs
    The noticed RTX scaling of 99.79% for 2 GPUs, 97.69% for 4 GPUs and 93.75% for 8 GPUs

    Click image for larger version

Name:	Screenshot_2023-11-06_at_1.13.21_PM.png?ex=662f80ed&is=661d0bed&hm=da1a8bbd49c6f6093858d3e2322e2b82409d269acc28764da0be64047f9c730d&.png
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    Conclusion,

    V-Ray GPU scales near linearly across multiple GPUs. We have recorded an average of 97% with 4 GPUs and 91% with 8 GPUs, the highest efficiency is usually found when combining GPUs of the same generation and of similar performance.​ Furthermore, we recommend having 6 physical cores at least per GPU when setting up machines with multiple GPUs, new CPUs and motherboards with PCIe 4.0 could be helpful

    Best,
    Muhammed
    Last edited by Muhammed_Hamed; 17-04-2024, 01:38 PM.
    Muhammed Hamed
    V-Ray GPU product specialist


    chaos.com
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