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Thread: LW 2018 only using 70% cpu when rendering.

  1. #1
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    LW 2018 only using 70% cpu when rendering.

    Can anyone tell me why Lightwave 2018 only uses 70% of my cpu when I render. I have a thread ripper 1950x and have set my threads to 32 but notice that it is not firing on all cylinders.
    I have just checked Seems a waste if I am not using all of my processing power. Is there some setting I am missing that will put all of my computer on to the task?

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    Have you tried any other LW version than 2018 or any other rendering software while having the same issue, or is it only in LW 2018?

  3. #3
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    What are you rendering? And how long it takes (per frame).. ?
    If it takes seconds per frame, CPU is busy writing files to disk.
    Do you have SSD or HDD? network disk?
    LightWave Plugins
    Global Materials for LightWave 2019
    Custom plugin writing. Request a quote.

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    you put that fix on that some dude made to make threadripper work properly on windows ?

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    I have tried on 11.6, and 2015 which seem to render at 97-100% Blender also uses everything. I have tried different scenes in lw2018 they vary 70-80% Start off at 100% for a couple of seconds and then tail off.
    I have ssd drives .
    I have not heard of a Threadripper fix? Any ideas where that is?

  6. #6
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    Sensei, I forgot to mention this is rendering high res stills. I have tried different tile sizes as I wondered if there was some down time between tiles but it has made no difference.

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    sorry, its for the 2990x

    https://bitsum.com/portfolio/coreprio/

  8. #8
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    I have just done a bit more testing. If I render the same scene on a dual xeon (24 threads) it sits at 100% throughot the render.
    If I render the same scene in LW 2019 I see a small improvement. 90-95% for the preprocess, 85- 90% for the second phase and 75-80% for the adaptive sampling. There definitely seems to be a problem with a 32 thread Threadripper for the rendering/ antialiasing phase of the render.

  9. #9
    Super Member Qexit's Avatar
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    As I only have Intel CPUs, I cannot investigate the problem firsthand. However, I did find this description of the different modes available for the 1950X chip that could shed some light on the problem and a possible solution:

    https://www.anandtech.com/show/11697...1920x-review/4

    The UMA/NUMA switch looks to be worth investigating.
    Last edited by Qexit; 03-21-2019 at 08:14 AM.
    Kevin F Stubbs

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    Tl;dr?

  11. #11
    Super Member Qexit's Avatar
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    Quote Originally Posted by gar26lw View Post
    Tl;dr?
    Well, this is the section that caught my attention:


    ' Legacy Compatibility Mode, on or off (off by default)
    Memory Mode: UMA vs NUMA (UMA by default)

    The first switch disables the cores in one fo the silicon dies, but retains access to the DRAM channels and PCIe lanes. When the LCM switch is off, each core can handle two threads and the 16-core chip now has a total of 32 threads. When enabled, the system cuts half the cores, leaving 8 cores and 16 threads. This switch is primarily for compatibility purposes, as certain games (like DiRT) cannot work with more than 20 threads in a system. By reducing the total number of threads, these programs will be able to run. Turning the cores in one die off also alleviates some potential pressure in the core microarchitecture for cross communication.

    The second switch, Memory Mode, puts the system into a unified memory architecture (UMA) or a non-unified memory architecture (NUMA) mode. Under the default setting, unified, the memory and CPU cores are seen as one massive block to the system, with maximum bandwidth and an average latency between the two. This makes it simple for code to understand, although the actual latency for a single instruction will be a good +20% faster or slower than the average, depending on which memory bank it is coming from.

    NUMA still gives the system the full memory, but splits the memory and cores into into two NUMA banks depending on which pair of memory channels is nearest the core that needs the memory. The system will keep the data for a core as near to it as possible, giving the lowest latency. For a single core, that means it will fill up the memory nearest to it first at half the total bandwidth but a low latency, then the other half of the memory at the same half bandwidth at a higher latency. This mode is designed for latency sensitive workloads that rely on the lower latency removing a bottleneck in the workflow. For some code this matters, as well as some games – low latency can affect averages or 99th percentiles for game benchmarks.'

    Switching between UMA and NUMA should be straightforward but without access to the necessary hardware, I cannot be sure
    Last edited by Qexit; 03-21-2019 at 07:23 AM.
    Kevin F Stubbs

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    thanks kev

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    Great, thank you, I ll have a play with the settings and see how it effects things.
    Last edited by oatsey; 03-21-2019 at 07:51 AM.

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    I'll potentially be in the market for a Threadripper soon so I appreciate any updates and information you find. Researching it and finding out all the NUMA windows issues that apparently haven't been resolved makes me hesitant. I'm very interested in your findings.

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    I read somewhere that newer Threadrippers will switch automatically between UMA vs NUMA modes as needed.

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