To preface the issue, I'm not considering this to be a bug per se. Originally I had installed Krita on Windows and periodically while painting, the program would lock up for 1-2 seconds after a brush stroke. Kind of annoying, so I looked in to any workarounds or solutions. What I found is that if I upped the RAM usage from 50% to 75% (no noticeable performance hits to audio/video applications on the second screen as I have 16gb on my machine) and that pretty much took care of the issue in Windows 7.

I since then installed Ubuntu Studio which comes with my new favorite art program, Krita, already packaged in. Though I do grab the Appimage releases as they are more current than the release via Software Center. While overall function performs better, I've run into the same lockup issue only it randomly locks in between brush strokes as well. I attempted the above mentioned fix that worked in Windows, I have not been able to get around this little nagging problem.

What I am wondering is if anyone has any suggestions to try to optimize Krita's performance on Ubuntu?

Sounds like autosave or swapping.

Makes sense. I'll test things out and report if it's still locking up.