P: High CPU usage makes it unusable during export

Some ideas - update your motherboard as it could optimize how your CPU cores are tackling each IPC (instructions per clock).

Also, try setting the priority level of Lightroom to a lower level.  

It's not a complete fix, but I notice I can still use my computer a bit more while exporting 100+ photos.

Bob, some of us use this software professionally and don't want to resort to work arounds. This is a serious issue for heavy users and needs to be addressed by Adobe.

UNIX (the OS core of MacOS) is not a priority based, interrupt driven OS. Adobe would have to offer a setting to limit the number of parallel threads. 

I'm expecting it to use all my cores, but not on such priority that I can hardly move my mouse cursor...

If you really don't want to try any of the other tips above, why not start your export just before you go to bed?

Bob Frost

Hello,

I have the same problem, my PC (a DELL XPS 15 7590 with 32 GB RAM and 2 TB SSD) gets unusable while doing exports. I don't know this behaviour from other applications, working with other software should be possible while Lightroom is doing exports in the background. Of course the computer will get slower, but not unusable. What about a mechanism to lower down the priority when switching to other applications automatically, when Lightroom is losing the focus? Or an option in Lightroom about the priority. I'm working at home at the moment, because of Corona, as a developer for my company. And so it would be possible to do exports with Lightroom while working remote on my office PC. But it's not possible because of this problem. Very very annoying. 

I'm using Lightroom since the first version. In my opinion this problem is new since a few months, maybe...

Best regards
Friedemann

A computer is always waiting on something, otherwise everything would happen instantly. It is waiting on CPU, I/O, network, memory, etc. So when the cpu busy drops from 90% to 30% it is because it is waiting for something else such as reading or writing to disk. 
 
For example, I moved my Lightroom library and catalog to my GoogleDrive folder to have a cloud backup. Then with every update (adjusting a slider, etc), Google locked the appropriate file until the file was uploaded. Otherwise the file could get corrupted. To fix, I put a SSD on the PCIe bus, moved everything except the Lightroom Cache to that disk (dedicated to Lightroom), the cache is on a separate SSD, and use a file/folder synchronization program to periodically sync Lightroom with GoogleDrive. I use Second Copy 9.0. 
 

Rikk - Why on earth design a behaviour such that 'After restart lightroom will reach 90 percent but after 10 minutes of working it goes down to 10 to 30 percent.'?

Robert,

Can you post the URL to that article.  Thanks.

"it is cumbersome to change affinity using Windows Task Manager all the time."

A late reply that might be useful to you and others: You can create a .bat file that will start LR restricted to a subset of virtual/logical processors. For example:

start /affinity fff "c:\Program Files\Adobe\Adobe Lightroom Classic\Lightroom.exe" c:\Users\john\Pictures\Lightroom\Test\Test-2.lrcat

starts LR restricted to 12 virtual/logical processors / threads. The "fff" is a hexadecimal mask specifying the particular processors to use.

@echo off
REM Starts Lightroom with a process affinity. Replace 7 below with 1, 3, 7, 15, 31, 
REM 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, or 65535, to restrict
REM Lightroom to use 1, 2, 3, ..., 16 virtual/logical processors.
powershell "& ""c:\Program Files\Adobe\Adobe Lightroom Classic\Lightroom.exe"""
powershell sleep 10
powershell $P = Get-Process Lightroom; $P.ProcessorAffinity=7; $P.ProcessorAffinity; $P.Id

(The original commands I provided no longer work with Lightroom for some obscure reason I can't figure out.)