CS6 64bit - 'Step Backward/Forward' is slow

[Sendra]

Step Backward/Forward (Alt-Ctrl-Z/Shift-Ctrl-Z) is slow, usually 2 seconds while the basic Undo/Redo (Ctrl-Z) for that same brushstroke is instant. It still occurs on a tiny new 200 x 200 file with a single brushstroke. What's going on and how can I fix it?

System Information:

Processor - Intel(R) Core(TM) i5-6600K CPU @ 3.50GHz, 3501 Mhz, 4 Core(s), 4 Logical Processor(s)
RAM - 32 GB
Main Drive - Samsung SSD 850 PRO 1TB
Scratch Disk (Only used as a scratch disk, no other items on it) - Samsung SSD 850 EVO 250GB (Set to 90% usage in Photoshop)
Graphics Card - AMD Radeon R9 380 Series, drivers up to date
Tablet - Wacom Cintiq 22HD, drivers up to date

Photoshop Settings:

History & Cache Settings:
     History States - 20
     Cache Levels - 4
     Cache Tile Size - 128k
(I've fiddled with all these settings and nothing has fixed this problem)

Graphics Processor Settings:
     Use Graphics Processor - Checked
     Use Graphics Processor to Accelerate Computation - Checked
     Use OpenCL - Checked
     Anti-alias Guides and Paths - Checked
     30 Bit Display - Unchecked

[Trevor.Dennis]

Sendra  wrote

Scratch Disk (Only used as a scratch disk, no other items on it) - Samsung SSD 850 EVO 250GB (Set to 90% usage in Photoshop)

Are you confusing Scratch space with RAM?  I don't know of any way to allocate a specific percentage of a drive for Scratch space.

90% is on the high side, and even with 32Gb might be limiting your operating system of resources.  I also have 32Gb, and I have never seen Photoshop use all the 70% I have allocated, but I have seen substantial scratch files.  Your system is more than a match for even major Photoshop projects, and I wouldn't expect to see lag when toggling undo/redo.

Bring the RAM allocation down to about 70%, and you could easily take your history states to 100 or more.  Your cache settings are OK.

[Sendra]

Ah, yes, I was confusing scratch space with RAM. Thank you for correcting me on that, it makes a lot more sense now. I took your advice to turn the RAM allocation down, but no matter the setting (I tried 70%, 40%, and 20%) the step backwards/forwards lag is still there.

[Trevor.Dennis]

Sendra  wrote

Ah, yes, I was confusing scratch space with RAM. Thank you for correcting me on that, it makes a lot more sense now. I took your advice to turn the RAM allocation down, but no matter the setting (I tried 70%, 40%, and 20%) the step backwards/forwards lag is still there.

Open Photoshop > Preferences and click on the Scratch tab.  How quickly does it respond?  If not instantaneous, then it might indicate an issue with one or more of your drives.

Open File Explorer to the root directory of your scratch drive, and close Photoshop.  Are there any orphaned 'Photoshop Temp....' files left?  If yes, delete them.  You can see that I have just found such a file as a result of a power cut a few days ago.

Keep watching the scratch drive. Open Photoshop.  I am doing the same, and at this stage I have a 1.2Gb temp file

Create a large document (16bit 30,000 pixels square).  Mt temp file has grown to 7.6Gb

Add a new layer and fill with 50% grey.  My temp file is now 18Gb

Go Filter > Noise 400% followed by Filter Surface Blur.  This will take some time, even on your system.  My temp file is up to 30Gb and the surface blur took 201 seconds.

In fact open Task Manager > Resource Monitor  and check the CPU and Memory tabs while this is going on.  Mine topped out all 70% of RAM allocated to Photoshop, and 60% CPU.  I have a similar system to you, but with six cores (12 threads).

OK, the big reveal.  Undo the surface blur.  Mine was instant.  Redor the surface blur.  Mine was still instant.  The scratch file is still 30Gb, but was obviously not accessed to do the undo/redo.  That had to be happening in RAM.

Try those tests and get back to us.

BTW  You gave us some of your GPU settings, but what the Advanced settings, Drawing Mode etc.?

[Sendra]

While doing the big file noise/blur testing the step backwards/forwards lag suddenly disappeared, which is really weird since I've been having this problem for 2+ months and only came to the forums last night for help. I mean, I'm happy it's fixed, but I'm also confused as to what fixed it.

I'll still tell you what my testing and timing results were:
I don't have a 'Scratch Disks' tab under preferences, probably because I'm on CS6.
When I closed Photoshop, the temp file disappeared.
My 'Drawing Mode' is Advanced, I had tinkered by trying the other settings before and it didn't do anything.
On the large file: Paint bucket took 2 seconds, Add Noise was near instant, Surface Blur took 177 seconds.
In Resource Manager my CPU hovered around 95% and Photoshop maxed out on its 70% RAM allotment.

The largest the temp file got to during this test was 30.5 GB.
And when I went to step backwards/forwards (alt+ctrl+z, shift+ctrl+z)... it's now all suddenly instant, no more 2 second+ delay. Before only undo/redo (ctrl+z) worked properly without lag.
I did further tests by bringing up some of my digital paintings and files to test brush strokes and they're all instant step backwards/forwards now, too.

Thank you so much for your help Trevor. I'm not quite sure what did it, but something fixed it! I'll reply to this topic again if the problem returns.