Lightroom Classic 9.x: Using wrong GPU on Mac OS Catalina

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  • Updated 5 months ago
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  • (Edited)
I've found strange behavior of LR CC Classic 9.x under Mac OS Catalina. 
When LR is started it is using for GPU acceleration the Intel HD Graphics adapter and not the Radeon 5500 - although in performance preferences it says that Radeon is used.
Mac OS "This Mac" says that Intel HD is used as graphics adapter and all tools for monitoring performance and sensors also say that Intel HD is in use.
The situation changes if I press the "system info" button in LR's performance preferences - then the GPU is changed to Radeon 5500 (all system tools say that now Radeon is used) and LR gets a huge performance boost. 
Of course workaround for this is to disable Mac OS automatic GPU switching or connect external monitor which forces the switch to Radeon GPU. But this is not convenient. 
It seems that LR is not forcing the GPU switch on Catalina when started - it happens only when "system info" is launched (and GPU stays switched till LR being closed).
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Pawel Guraj

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Posted 7 months ago

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Richard Hix

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Guess I followed some guru's suggestion to select Use Graphics Processor "Custom" under the Performance tab and check "Use GPU for image processing" The next line then reads "Radeon Pro Vega" followed by "Full Graphics acceleration is enabled."  So, I'm always using the GPU with LR.

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Rikk Flohr, Official Rep

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You already have. I've forwarded this thread to engineering with a request for review. 
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Pawel Guraj

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Thanks, I was not sure if this is the correct place.
Pawel. 
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Rikk Flohr, Official Rep

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From engineering:  Generally speaking, Lightroom (and Camera Raw) do not select which GPU to use, they just use the macOS default.

We will look into this further but it may ultimately be something that needs resolution in the OS. 
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Pawel Guraj

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Other apps are able to force MacOS to use higher performance GPU. Lightroom is also able to do that - it happens when "system info" button is pressed. 
It worked correctly on Lightroom before Catalina.

Br, Pawel.
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John Pane

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I am seeing the same behavior on a 2019 16" MacBook Pro with AMD Radeon Pro 5500M, running macOS Catalina 10.15.2.
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Pawel Guraj

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I've solved the problem by deteting the Lightroom preferences file (located in Library/Preferences) and configuring from scratch.
Now Lightroom switches the GPU automatically on startup.

Br,Pawel
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John Pane

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That did not fix the problem for me.
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John Pane

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Checking back in on this. After deleting my preferences file apparently didn't fix the problem, I restored my original preferences file. Today, I discovered that Lightroom is now switching to the discrete GPU when I enter the develop module. It was not doing this before, so apparently something did change yesterday when I deleted (then restored) the preferences. Unfortunately, hadn't fully tested this when I made the report yesterday. This may be a pathway to getting it to behave in the desired way.
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Pawel Guraj

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Yep, same here. I was not precise. In my case deleting preferences caused LR to switch to AMD GPU automatically but only in Develop module.
Library module still uses Intel GPU