P: Quick Develop VERY slow on my system (6 sec vs 1 sec in LR 5.7)

Simon - I am experiencing the same frustrating slowness - I am running a brand new machine and "build standard previews" takes approximately 9 seconds to build a single preview. When trying to work on a wedding of over 2300 initial images, this is excruciating compared to the dozens per second previews that LR 5 was able to generate. This is but one specific example of the slowness I'm experiencing with LR CC - having been a user for almost 5 years now, I've employed all of the recommended optimizations. Sync, Address, and Face detection are all paused (no change in slowness). Here are my system specs to help illustrate the problem:

Lightroom version: CC 2015.0.1 [ 1018573 ]
License: Creative Cloud
Operating system: Windows 8.1 Business Edition
Version: 6.3 [9600]
Application architecture: x64
System architecture: x64
Logical processor count: 16
Processor speed: 2.9 GHz
Built-in memory: 32655.5 MB
Real memory available to Lightroom: 32655.5 MB
Real memory used by Lightroom: 6124.4 MB (18.7%)
Virtual memory used by Lightroom: 6532.4 MB
Memory cache size: 5742.6 MB
Maximum thread count used by Camera Raw: 8
Camera Raw SIMD optimization: SSE2,AVX,AVX2
System DPI setting: 144 DPI (high DPI mode)
Desktop composition enabled: Yes
Displays: 1) 4096x2160, 2) 4096x2160
Input types: Multitouch: No, Integrated touch: No, Integrated pen: No, External touch: No, External pen: No, Keyboard: No

Graphics Processor Info:
GeForce GTX 980/PCIe/SSE2

Check OpenGL support: Passed
Vendor: NVIDIA Corporation
Version: 3.3.0 NVIDIA 353.06
Renderer: GeForce GTX 980/PCIe/SSE2
LanguageVersion: 3.30 NVIDIA via Cg compiler

Application folder: C:\Program Files\Adobe\Adobe Lightroom
Library Path: H:\2015 Catalog\2015 Catalog\2015 Catalog-2.lrcat
Settings Folder: C:\Users\Kenneth\AppData\Roaming\Adobe\Lightroom

Installed Plugins:
1) Behance
2) Canon Tether Plugin
3) Facebook
4) Flickr
5) Leica Tether Plugin
6) Nikon Tether Plugin
7) SmugMug

Config.lua flags: None

Updated Toolkit: Adobe Camera Raw 9.0 for Lightroom 6.0 (build 1014445)
Updated Toolkit: Book Module 6.0 (build 1014445)
Updated Toolkit: Develop Module 6.0 (build 1014445)
Updated Toolkit: Import Module 6.0 (build 1014445)
Updated Toolkit: Library Module 6.0 (build 1014445)
Updated Toolkit: Map Module 6.0 (build 1014445)
Updated Toolkit: Monitor Module 6.0 (build 1014445)
Updated Toolkit: Print Module 6.0 (build 1014445)
Updated Toolkit: Slideshow Module 6.0 (build 1014445)
Updated Toolkit: Web Module 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.AgNetClient 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.AgWFBridge 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.Headlights 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.LibraryToolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.MultiMonitorToolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.archiving_toolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.bridgetalk 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.catalogconverters 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.cef_toolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.coretech_toolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.curculio 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.discburning 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.email 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.export 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.ftpclient 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.help 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.iac 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.imageanalysis 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.layout_module_shared 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.pdf_toolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.sdk 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.sec 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.socket 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.store_provider 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.substrate 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.ui 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.video_toolkit 6.0 (build 1014445)
Updated Toolkit: com.adobe.ag.xml 6.0 (build 1014445)
Updated Toolkit: com.adobe.wichitafoundation 6.0 (build 1014445)
Adapter #1: Vendor : 10de
Device : 13c0
Subsystem : 111610de
Revision : a1
Video Memory : 3896
Adapter #2: Vendor : 1414
Device : 8c
Subsystem : 0
Revision : 0
Video Memory : 0
AudioDeviceIOBlockSize: 1024
AudioDeviceName: Speakers (Sound Blaster Recon3Di)
AudioDeviceNumberOfChannels: 2
AudioDeviceSampleRate: 44100
Build: LR5x102
Direct2DEnabled: false
GPUDevice: not available
OGLEnabled: true

LRCC grinds to a halt whenever I'm in the Devlop module and attempting to use any brush or tool. I'm so displeased and frustrated with LRCC that I'm considering going back to LR5. I've tried all of the suggested tweaks and "fixes" and none of them work.
Hopefully, we can get an actual Adobe employee to investigate why LRCC gets slower with every update. At this point, it has slowed my workflow by almost 90% when it should be speeding up my workflow by at least 50%.

The catalog size is small, only 40MB. Face Detection and mobile sync are off. It does start responsive, then becomes slower after only a few minutes within the same session. I've tried optimizing and nothing changes. The preview size are 'medium' 1920px.

What is the size of your catalog? Do you have Lr mobile sync turned on? Automatic face detection turned on? Does Lr start responsive and become slower and slower over time within the same application session? Have you tried optimizing the catalog? What preview size did you specify when you import?

i7 4770k @ 3.5ghz, 16gb ram, Dell u2410, Windows 7, 4GB GTX 970, EVO 840 250GB ssd

LRCC gets slower the more I use it. After just 20 minutes, the Library module is very slow. Selecting multiple photos takes many seconds just to complete the selection and the 'sync settings' button only becomes active after a few seconds. Very sluggish and slowing down my workflow big time.

Thanks for the update, Simon.
Glad you guys are aware and following this thread, and doing what you can do to help.

This thread has digressed a little bit from the original report of quick develop being slower in some setup. I have a reproducible case of slow down when rendering a specific HDR floating point photo. I have logged a bug for investigation. It seems the noise reduction was the main culprit. Tons of local brush also added to the slowdown. The team is still investigating that.

The team also investigated other reports of performance slowdown in 6.0 and has made a few fixes.

When reporting performance issues, it is important to be as specific as possible in describing your computer and Lightroom setup, usage scenarios, test files etc so that the team have something concrete to follow up with and try to reproduce. It might require a bit of experiment on your part to try to isolate as much as possible.

There is some Lighroom performance optimization tips https://helpx.adobe.com/lightroom/kb/... that you can try to experiment with.

Simon, any update? Last we heard was a month ago.

You mean other than Simon Chen, the engineer who commented above?

Is there anyone from adobe here reading this thread? It would be nice to hear some acknowledgement of this issue, and better yet to hear that they are working on a fix.