Hyperthreading and Previews

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  • Updated 12 months ago
  • (Edited)

Greetings from Germany,

I'm using a HP Workstation Z440 with a SixCore Intel Xeon E5 1650 v3, with
32 GB of ECC RAM and a nVidia Quadro K4200 graphics card as well as the latest updates.

If I turn off hyperthreading in the BIOS and have not set the hook for parallel creation of previews in Lightroom, then, as it should be, first the images are copied and then the previews are created.

But if I turn hyperthreading on, the hook does not stay set, nevertheless a parallel preparation of the previews takes place.

Can someone explain why that is? The support had no answer.

Thanks in advance!



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Christopher Kesting

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Posted 12 months ago

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Simon Chen, Principal Computer Scientist

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Intel Xeon E5 1650 v3 has 6 cores. With HT on, it will support 12 threads. Lightroom will do performance scaling based on the number of physical/logical cores. Typically 8 logical cores is a threshold point to scale up doing more in parallel in this particular situation.

You should see Lightroom's reported core use in Lightroom>Help>System Info...
(Edited)
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John R. Ellis, Champion

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To test my understanding of what you're observing:

1. With hyperthreading off in the BIOS (6 logical processors) and the option Preferences > Performance > Generate Previews in Parallel unchecked, you observe previews generated sequentially.

2. With hyperthreading on in the BIOS (12 logical processors) and the option Preferences > Performance > Generate Previews in Parallel unchecked, you still observe previews generated in parallel.

Is that correct? Smells like a bug. To get everyone on the same page, please provide additional details:

- Is the preview generation occurring as the result of an import?  If so, please post a screenshot of the File Handling panel from the Import window, e.g. 



- Is the option Preferences > General Replace Embedded Previews With Standard Previews During Idle Time checked or unchecked?

- Can you please post the first ten lines from Help > System Info for both scenarios (1 and 2)?  

- Can you please post screenshots  for both scenarioes (1 and 2) of the CPU utilization graphs from Task Manager > Performance > CPU (Windows ) or Activity Monitor > CPU > CPU Load (Mac)? E.g.





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Christopher Kesting

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1. With hyperthreading off in the BIOS (6 logical processors) and the option Preferences > Performance > Generate Previews in Parallel unchecked, you observe previews generated sequentially.

2. With hyperthreading on in the BIOS (12 logical processors) and the option Preferences > Performance > Generate Previews in Parallel unchecked, you still observe previews generated in parallel.

Is that correct?

That is correct.


Is the preview generation occurring as the result of an import?
Yes


If so, please post a screenshot of the File Handling panel from the Import window, e.g.

I have tested this with 111 raw files in a row of the 1D X Mark II. I have repeatedly imported these again, then deleted and optimized the database. And I did that twice.


- Is the option Preferences > General Replace Embedded Previews With Standard Previews During Idle Time checked or unchecked?

Always unchecked, since beginning!


- Can you please post the first ten lines from Help > System Info for both scenarios (1 and 2)? 

You don't believe me?
6 Core:
Lightroom Classic-Version: 8.3.1 [ 201905241238-dcd7e2de ]
Lizenz: Creative Cloud
Spracheinstellung: de
Betriebssystem: Windows 10 - Business Edition
Version: 10.0.18362
Anwendungsarchitektur: x64
Systemarchitektur: x64
Anzahl logischer Prozessoren: 6
Prozessorgeschwindigkeit: 3,4 GHz
Integrierter Speicher: 32684,1 MB

12 Core:
Lightroom Classic-Version: 8.3.1 [ 201905241238-dcd7e2de ]
Lizenz: Creative Cloud
Spracheinstellung: de
Betriebssystem: Windows 10 - Business Edition
Version: 10.0.18362
Anwendungsarchitektur: x64
Systemarchitektur: x64
Anzahl logischer Prozessoren: 12
Prozessorgeschwindigkeit: 3,4 GHz
Integrierter Speicher: 32684,1 MB




6 Cores:


12:




FYI: I'm using LR since the Beta Version in January 2006. Since a few days I write an article in my blog about the performance of Lightroom. As a photographer and lecturer for photography, I try to bring thes Prgromm closer to my seminar participants. That's why I'm testing a few things right now.


Thank you for your efforts!


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John R. Ellis, Champion

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Excellent -- that detail helps everyone understand what you're observing.
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John R. Ellis, Champion

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The two CPU graphs look similar.  With 6 logical processors (virtual cores), the instantaneous utilization was 36% (the equivalent of 2.6 cores).  With 12 logical processors, the instantaneous utilization was 32% (the equivalent of 3.8 cores). What symptoms are causing you to think that previews are being generated sequentially with 6 logical processors but in parallel with 12 logical processors?
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Christopher Kesting

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To make it even clearer ;-)

Preferences > Performance > Generate Previews in Parallel unchecked

Here with HT:



Without HT Lr is just copying and then generating previews.

(Edited)
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Simon Chen, Principal Computer Scientist

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What is your import Build Previews size setting? Is it Embedded & Sidecar? 
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Christopher Kesting

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I'm fine that it works in parallel, very much, I was just wondering about it.
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Christopher Kesting

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I don't see that in your previous posts -- it must have gotten dropped. | No you're right I forgot that.

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Simon Chen, Principal Computer Scientist

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Thank you both!
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Christopher Kesting

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So that means if I have more than 8 cores, the checkbox is ineffective, because Lightroom does that automatically?
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Simon Chen, Principal Computer Scientist

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Yes, for the import case that you are reporting.