CPU Usage on 100% During Export

[AzzBlock]

When exporting my RAW images to JPEGs to send to clients Lightroom uses up all of the available CPU power which makes the mouse stutter and makes it very hard to do any other task whilst the export is occuring.

This is not a new problem. It has been happening for quite a while now since version 6 or 7, I can't remember exactly but I do know this wasn't a problem with older versions of Lightroom before the Adobe Subscription service.

I've tried enabling/disabling GPU utilization and that made no difference.

I own an Intel i7 3.4GHz CPU so lack of power isn't the problem.

[johnrellis]

GPUs are power hungry, so from a total heat perspective, moving the exports from the CPU to the GPU may be a smaller relative win that at least I first thought. 

For example, my computer has an Intel Core i9 (8 cores) with maximum power of 45 W and an AMD Radeo Pro Vega 20 with a maximum power of 100 W.

Casual eyeballing of a performance monitor on my computer shows that exports of large raws without GPU use about 80% CPU.   Enabling the GPU for export significantly reduces CPU utilization to about 30% while using the GPU at about 20%.   Thus, very crudely, using the GPU reduces total power used from 36 W (80% * 45 W) down to 33.5 W (30% * 45 W + 20% * 100 W), a 7% net savings in total power. (This assumes of course that power is linearly proportional to utilization, a reasonable assumption on multi-core CPU and GPUs.)

This is clearly a back-of-the-envelope calculation, whose particulars will vary significantly across different hardware, but I think it's directionally accurate.

[johnrellis]

"continue to add GPU acceleration to other areas ... such as rendering previews and thumbnails, face recognition, etc."

Adobe says that LR already uses the GPU "to speed up tasks of displaying and adjusting images in the Develop module, the Library module's Grid view, Loupe view, and Filmstrip."  Though I don't see the GPU being used at all for those things on my Mac.

[ManiacJoe]

One way to get LR to play better with the other tasks is to use the OS tools to lower the priority of the program to "below normal" or the like before starting the export. This will allow LR to use up all the available CPU cycles while giving priority to the other programs and the OS.

[johnrellis]

Many have complained that LR is unusable during exports, and sometimes their entire computer is unusable:

https://feedback.photoshop.com/photoshop_family/topics/classic-cc-uses-90-cpu-during-export

Please add your constructive opinion and details of your issue to the bug report, and be sure to click Me Too and Follow in the upper-right corner. That will make it a little more likely that Adobe will prioritize a fix, and you'll be notified when the bug's status changes. (Simply linking back here will generally be ignored by Adobe.)

There have been a few statements by Adobe employees over the past several years that, after Export was changed in LR 6 / CC 2015 to use multiple cores more effectively, they intended that Export would consume most but not all of the available CPU, which would allow for interactive use.  I found one of those statements here:
https://feedback.photoshop.com/photoshop_family/topics/lr-cc-2015-2-and-up-cpu-usage-on-export-on-25...

See this post for a workaround that restricts LR to using a subset of the virtual/logical processors:

https://feedback.photoshop.com/photoshop_family/topics/classic-cc-uses-90-cpu-during-export?topic-re... 

E.g. if you have 16 processors, restricting LR to use 12 is a good compromise, leaving 4 for interactive use, while still letting export and merges use most of the computer.

[Use the blue reply button under the first post to ensure replies sort properly.]

[Rikk Flohr: Photography]

Changes were made with the release of Lightroom Classic 11.4 to shift part of the Export processing load to the GPU. As a result, CPU utilization should change for some operations.