How to speed up Lightroom face detection?

Question

I am using Lightroom (Windows) to tag all of my pictures using face detection, however I have 80,000 pictures and it is going very very slowly. Looking at task manager it appears to process an image and then have the CPU idle for 8 or 9 seconds. Any ideas as to what the bottleneck might be? Or some way to speed this up? My guess is that LR just does not have a good face detection pipeline and I just have to deal with it but I wanted to see if this is normal or if there are tips on how to speed things up.

My images/lrcatalog/cache are all on a large NVME SSD. Below is a task manager screenshot. After noticing the GPU following suit with the CPU, I disabled GPU usage just in case transferring data from the CPU to the GPU was causing issues but it didn't help. The C drive is the primary drive with all the data.

Answer 1

Here's my photography-centric answer. How often do you need to do this? Pretty much just once for the full collection. Maybe the equivalent once every few years. At 10 seconds an image, this is going to be done in under ten days.

So, just let it go and worry about something else for ten days.

I know this goes against the generally-admirable instinct to do things efficiently, but sometimes, letting it go is the right move. It's a case of this xkcd:

... where "how often" is "once".

Now, of course, from Adobe's point of view, this is something that their software does quite a lot, when you consider all of their userbase and use-cases. So, the equation is different for them — and I wouldn't be surprised to see this get better in a future release.

In the meantime, though, just let it crank and find something else to do with your time.

Answer 2

A quirk that I have found with the Lightroom versions I have used [LR3 through Classic'19 at time of writing] is that they've been designed to 'play nice' with other programs by not willingly sucking up every last resource they can get their hands on.

Instead they will use a moderate resource level to avoid bogging the system down entirely and preventing you from using other programs while LR chugs along crunching numbers in the background. [Others will say that Adobe just failed to design it around a multithreaded workload... But that's another matter.]

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A work-around to this design choice is to be a little more hands-on with how you schedule tasks you assign to Lightroom by grouping your work into multiple batches that you then ask Lightroom to work with.

Instead of selecting everything you want done in one go [Import/Export/Applying Presets/Processing Facial Recognition/etc], select 1/3rd of it at a time and ask Lightroom to do the task. Then select the next third and get it rolling, then the final third.

Lightroom will then typically use a larger portion of overall system resources in this case, as you've specifically told it to run parallel tasks, and in my experience will result in completing things sooner.

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The exact split you use will depend on your personal hardware and what else you have going on the system at the time. It is worth experimenting with, and of course is subject to change with new versions of the software.

Keep in mind that large batches of photos IS a big chunk of number crunching, and there is only so much that can be done to track down bottlenecks or options to speed things up.