[Bug 105425] 3D & games produce periodic GPU crashes (Radeon R7 370)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=105425

--- Comment #7 from MirceaKitsune <sonichedgehog_hyperblast00 at yahoo.com> ---
I've been testing this crash using Xonotic during the past two days, granted
it's a game I have a lot of experience customizing. What I found is pretty
interesting and should be a good start in shedding light on this bug.

Initially the system freeze occurred somewhere between 10 and 40 minutes. Upon
changing a few cvars, I seem to have almost entirely gotten rid of it: After
nearly 5 hours of continuous testing, only one lockup has taken place! Below
are the cvar overrides I added to my autoexec.cfg for the test: At least one of
them had an influence... I'm still working on pinning down which, and that will
take several more days due to the probability rate of the issue.

r_batch_multidraw 0 // old: 1
r_batch_dynamicbuffer 0 // old: 1
r_depthfirst 0 // old: 2
gl_vbo 0 // old: 3
gl_vbo_dynamicindex 0 // old: 1
gl_vbo_dynamicvertex 0 // old: 1
r_glsl_skeletal 0 // old: 1
vid_samples 1 // old: 4
gl_texture_anisotropy 0 // old: 16

I know the issue has something to do with triangles or vertices: The crash
seems more frequent when there are a lot of players or objects present,
indicating that an increased surface count may be a contributor. I've suspected
mesh data stored on the video card to be the culprit, especially shared data
with multiple objects using one instance of a mesh from video memory. This is
why my bet is currently on gl_vbo (Vertex Buffer Objects /
GL_ARB_vertex_buffer_object) being the variable that made a difference... again
I still got a lockup even without it, so if anything it just heavily mitigated
the crash.

This belief is reinforced by my previous experience in Blender: The only scene
causing the GPU lockup is one where several high-poly objects share common mesh
data, and the crash always occurred upon me adding a Subdivision Surface to
just one of them (increasing its polygon count). It's been confirmed that as of
Blender 2.77 (I have 2.79) VBO is indeed enabled in the 3D viewport. Note that
I was also using the untextured viewport, thus I doubt textures play a role.

Lastly I ruled out the possibility of overheating having anything to do with
it: During the first 3 hours in which I got no lockup, the temperature in my
room was above 26°C. When I did get that one lockup later at night, the
temperature of my room had long dropped to 23°C. The stress on the GPU was the
same at all times, absolutely no settings were changed including the map.

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