CPU Usage

Discussion in 'Mac Pro' started by rueyloon, Dec 9, 2014.

  1. rueyloon macrumors regular

    Joined:
    Sep 24, 2013
    #1
    Question

    I'm running FCPX export on a 12 core and I see the top 2 processes as

    1) Transcodertool - around 600% CPU
    2) FCPX - around 300% CPU

    Does it mean 6 cores are fully utilised ? (overlapping)
    or
    Does it mean 9-10 cores are fully utilised ? (non overlapping)


    What will happen if this process is run on a 10 core ? or 8 core ?


    Just still trying to understand the core vs clock speed thingy.

    rgs
    rueyloon
     
  2. jdphoto macrumors 6502

    jdphoto

    Joined:
    Jan 13, 2014
    #2
    If I'm not mistaken you are using 9-10 cores. Things shouldn't "overlap" unless you've run out of cores. What does it show for your overall CPU usage? Is the user + system around 75%?
     
  3. rueyloon thread starter macrumors regular

    Joined:
    Sep 24, 2013
    #3
    So if this process is running on a 10 core processor, will it still use the cores in the same way ? or will it only run to say a max of 8 because 2 is always reserved for OS and other background stuff ?

     
  4. AidenShaw macrumors P6

    AidenShaw

    Joined:
    Feb 8, 2003
    Location:
    The Peninsula
    #4
    There are no reservations

    There is no concept of "reserving cores" in any modern mainstream OS. (And even though much of OSX is based on 1970's UNIX systems, it counts as "modern" due to the continual adoption of improved code.)

    The scheduler dynamically assigns computable threads to idle cores -- it will never leave a core idle if there are threads ready to compute.

    If a particular thread (say an "OS thread") is of higher priority than other threads waiting for a core - then that thread will be scheduled before "normal" or "background" threads.

    So - important threads will get preference, but the idea of a static "these cores are for the OS" allocation is simply not true.
     
  5. jdphoto macrumors 6502

    jdphoto

    Joined:
    Jan 13, 2014
    #5
    Exactly what he said. Threads are allocated as needed, nothing is reserved.
     
  6. AidenShaw macrumors P6

    AidenShaw

    Joined:
    Feb 8, 2003
    Location:
    The Peninsula
    #6
    clarification

    Actually, "hard affinity" is a way of reserving cores - but it is seldom used except in very specific circumstances (such as when you know that certain cores share levels of the cache hierarchy or NUMA nodes, and you want to make sure that some sets of threads share the same cache or NUMA).

    In general, manually mucking around with affinity will hurt performance - you'll have idle cores while threads are waiting for cores.
     
  7. rueyloon thread starter macrumors regular

    Joined:
    Sep 24, 2013
    #7
    Hi, thanks for all the answers, but is the method I used a good way to estimate optimal system configuration ? Like it seems like 10 cores is the optimum configuration for THAT process that I've shown. Or the whole thing will be jumbled up again when the computer sees a different number of cores for it to use ?

    rgs
    rueyloon
     

Share This Page