Using Multiple Threads is making my render slower

Taking advantage of multiple cores can be a great way to speed up long renders. However, there are certain things to take in consideration.

Speed gains will be much more pronounced on comps with multiple effects, especially if they are CPU-Heavy. Comps with no effects render at the same speed as a single thread because they’re limited by the transfer speed of the hard drive or network, not by the CPU. And for video outputs, they can be slower because of the additional step of converting the frames made by all the threads into a single file.

Performance also depends on other factors. The main one being the amount of RAM in the system. Make sure you have enough RAM to run all the instances of After Effects you desire.

The optimal number of threads is high enough so that your CPU is at 90-100%, but not so high that each thread is starved of RAM. For example, with 32GBs of RAM, running 4 threads means each one gets up to 8GBs, which works well for small to medium comps, but for big comps less threads is better.

The main panel includes a display of the RAM and CPU usage for convenience (GPU monitoring for NVIDIA-based systems). If you set the Thread Bossing Style to any of the automatic modes (Relaxed, Balanced, Demanding and Dictator), Render Boss will monitor the RAM and CPU being used to try and find the optimal level of threads with different levels of aggressiveness.

If you know your system well, or you just want to experiment, try setting the thread numbers manually and seeing what results you get. We’re currently working on a new version of the automatic thread management that uses A.I. to learn the optimal number of threads based on the effects used, which we believe will be a better system, but it’s in early stages at the moment.

There are certain projects that use huge amounts of RAM. In this case, a single thread can eat up all the available RAM, and adding more will choke the system. Additionally, certain effects are already optimized to use all your cores and/or the GPU.

In these cases, it’s much more effective to run only one or two threads and add a second computer / laptop. Even if a machine is much slower than the main workstation, adding a second machine usually performs better than starving your faster main machine of resources by adding too many threads.

Alternatively, certain effects let you limit the resources they use. In this case you can optimize those values for the amount of threads you want to run.

For instance, Neat Video (a popular denoiser) lets you specify how many CPU cores, and how much GPU Memory to use. So if you have 8 cores and you’d like to use 4 threads in Render Boss, you can set Neat Video to use 25% of GPU Memory and 2 cores. Setting it this way, Neat Video will use all your cores without choking your system, and you’ll still be able to run 4 threads of After Effects, speeding up the rest of the effects.