Lightroom: Your research source is flawed!

category: Lightroom • 2 min read

  1. Yes, Lightroom supports multiple CPUs since Lightroom 3.
  2. No, Lightroom is not a multi-threaded application. This means that Lightroom cannot spread a task between multiple thread or multiple CPUs.

See: What Kind of Computer/CPU to Get for Lightroom by Syv Ritch aka me

I wrote that blog post to which I got:

I’m running dual quad cores (8 processors) and LR uses all 8 cores.

I still stand behind my statements. Take a very close look at:

Lightroom: CPU Usage

Lightroom: CPU Usage

  1. Select a peak on any of the 4 CPUs that’s at one the vertical division of the screen.
  2. Take a look at the other 3 CPUs at the same division. You will see that the peak is at a slightly different offset.

What’s happening here is that the OS is waiting for the CPU, and instead of waiting for the CPU, it’s switching to the next CPU.

A “real” threaded application would launch a task on the first thread available, the next task in the next thread… So if we are talking about importing photos, Lightroom would be processing multiple photos at the same time. It would also render the previews of as many photos as there are threads available. It’s not. When looking at the importing or the preview generation, you can see Lightroom processing one photo at a time.

Here’s my setup: 1. I run an Intel i7 core with 4 embedded CPUs with hyper-threading. As far as the operating system is concerned, it looks like 8 CPUs. 2. I run Windows in a virtual partition with Vmware Workstation. So if anything happens, it will not affect the rest of the computer. Windows doesn’t know anything about the real computer. 3. I also have other tools to analyze CPUs, on the Linux side.

Some people will try to blame it on my VMware. It’s not. I’ve checked at some friends both on Mac and Windows and the same thing happens.