2 Replies Latest reply on Feb 23, 2014 1:12 AM by Rick Gerard

    Weird multi processing behavirn

    chfilm2 Level 1



      I got my new Mac pro yesterday and already got to work on the first project. Yes it's fast. I had a maxed out 2012 iMac and the nMP renders comps almost twice as fast IF using all cores properly. And it did for the first project I tested, which was mainly a compositing shot.


      But now I have a new project, consisting of a guy with keylight and some basic cc on him, a background video. Simple, and afx uses all cores almost at 100% until at one point there appears an overlay wit some blurred reflection, a drop shadow and 6 still images plus two videos in it.

      Suddenly, CPU usage drops down almost to 10%. It goes like this for a while, until it then goes up again with no obvious reason. Then, when the overlay goes away, up goes CPU usage to maximum again.


      I currently have multiprocessing setup as follows:


      Available cores: 16

      Available total ram: 64 gb


      Ram left for other apps: 8gb

      CPUs left for other apps: 8

      Ram allocation per core: 6gb


      I played around with several different setups, assigning less ram per core and not reserving any, but it got slower overall.


      Any ideas how I can determine what causes the not-utilization of my CPU horsepower? I know afx is poorly optimized but it bugs me that for no obvious reason, in the middle of the comp, CPU use breaks in so dramatically..(without multi core it was even slower)

        • 1. Re: Weird multi processing behavirn
          Mylenium Most Valuable Participant

          Search the forum. Seriously. We have been over it a million times. A single temporal effect can cause this behavior. A single non-threaded Codec can cause this behavior. Simple transfer bandwidth exhaustion can cause it. GPU-accelerated features can cause it. whatever. You have not provided nearly enough info to even begin to guess and your statement is vague. In any case. It is probably perfectly logical and you will have to live with it.



          • 2. Re: Weird multi processing behavirn
            Rick Gerard Adobe Community Professional & MVP

            What Mylenium said. MP works effectively within a very narrow of parameters. Until everyone that writes code for video and image compression/decompression, creates a plug-in for AE, or authors any program you may choose to upload to your computer gets fully on the optimized for multi processor processing bandwagon MP is going to break if you throw one think in the system that is not compatible. We are a long time from being able to utilize every bit of power available in a processor and every bit of memory in a system is going to be able to be harnessed for processing a frame of video that is less than 40MB in size. (a full frame of 4K is 36.5 MB in size) Ask yourself how fast the buss would have to be to push enough 40GB frames through 8 GB of ram per clock cycle to saturate 8 64 bit cores on every clock cycle, and even that would only utilize half of your systems power.