The Version: 3.0 Beta (git 962bfe1) build has been giving me a rough time performance wise today (filed another bug report about it today). 

I've been using it for the past five hours and during the last two it has basically become unusable.

Changing the visibility of 3 Adjustment  Layers takes about a minute. Changing the order of layers is also very slow and sometimes crashes Krita. I have found a partial workaround to this by hiding the visibility of layers before changing their order.

The Polygon and Brush tools get stuck often.The brush tool "chooses" to paint on its own after I end a stroke and the polygon tool jumps around or does not register a click making it almost unusable. 

Then Krita becomes unresponsive on file save. On program restart it threw me this error:
Krita could not initialize the OpenGL canvas:
Checker vertex shader
Vertex shader failed to compile with the following errors:
 Krita will disable OpenGL and close now.

I think that I'm done testing this build and going back to the previous one. 

I'm on an old Toshiba Satellite laptop running Windows 7 32bit and using a Wacom Intuos. I am aware that it's not the fastest system around but I never had these kind of problems  with the previous builds of Krita 3.0 and I've spent quite a bit of time testing them. 

Reproducible: Sometimes

Steps to Reproduce:
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