I have been using lightroom for years now. Currently running CC on a 1 year old Envoy with upgraded ram, dual 19 inch LCDs. Working with raw photos from a d600. The only extras are the Smugmug Plugin currently up to date and a few presets. If I open lightroom it uses about 300,000k of memory, within an hour of proccessing roughly 200 photos with lightroom not using the second display its up to 2,000,00+ at idle and runs choppy.
Is this normal? For a decent PC I would love to not sit waiting for a program to "gather info" just to delete a file.
Lightroom version: CC 2015.1.1 [ 1032027 ]
License: Creative Cloud
Operating system: Windows 7 Business Edition
Version: 6.1 
Application architecture: x64
System architecture: x64
Logical processor count: 8
Processor speed: 3.3 GHz
Built-in memory: 32224.6 MB
Real memory available to Lightroom: 32224.6 MB
Real memory used by Lightroom: 1239.0 MB (3.8%)
Virtual memory used by Lightroom: 1221.4 MB
Memory cache size: 1189.2 MB
Maximum thread count used by Camera Raw: 4
Camera Raw SIMD optimization: SSE2
System DPI setting: 96 DPI
Desktop composition enabled: No
Displays: 1) 1920x1080, 2) 1920x1080
same for me with 5.7.1 but now slowdown - even if LR uses more than 6 GB of my 16 GB machine.
I also have the problem. I'm using LR CC 2015.6.1 on a i7-3.4 GHz processor and Win 10 Pro. I have 16 Gb of RAM and regularly get "Memory short" messages after a moderate amount of use.The problem as been occurring for some time and doesn't seem to have been resolved (as promiseed) with the latest update.