Lightroom Export Running Slowly

When you’re in Activity Monitor, open the CPU History and GPU History graphs, both under the Window menu. During an export, watch what both graphs do. Recent versions of Lightroom Classic use GPU acceleration to speed up export, so if the Mac Pro has a supported graphics card, the GPU History graph should show substantial usage during export.

In addition, if the GPU History graph shows heavy usage during export, it is actually somewhat normal for the CPU graph to look less busy. That’s because if the GPU is able to accelerate the bulk of the processing, there isn’t much left for the CPU to do there.

It can seem counterintuitive, but if an application can apply GPU acceleration to a task, full GPU usage and low CPU usage can result in a much shorter processing time compared to low GPU usage and full CPU usage. That’s what I found when Lightroom Classic introduced GPU acceleration for export, and it’s consistent with what happens when GPU acceleration is added to other types of applications such as video editors.

In other words, if a computer can apply a specialized coprocessor (GPU, NPU, media engine…) to a task, that usually means making the CPU do it instead would be slower and hotter, so the task is taken away from the CPU, so reported CPU usage goes down.

But if the graphs show you that both CPU and GPU usage are very low during export, then that would be something unexpected that would need troubleshooting.

How slow? Tell us how long it takes to export X photos. What camera? JPG or RAW?

Also please tell us the version NUMBER of your Lightroom Classic. We need the version NUMBER and not words like "latest" or "up-to-date".