[Bug 111077] link_shader and deserialize_glsl_program suddenly consume huge amount of RAM

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111077

--- Comment #29 from Timothy Arceri <t_arceri at yahoo.com.au> ---
(In reply to roland at rptd.ch from comment #22)
> Hi Marek,
> 
> This is going to be complicated. The application is not yet free to use by
> others (working on getting it to release shape). I would have to figure out
> first how to break this down into a reproducible test case since I don't
> know myself what triggers the bug.
> 
> If you can think of some corner values to narrow down in what direction to
> search I can fully mess with the source code over here. The faulty commit
> talks about UBO maximum size so this might be a start. The OpenGL
> Capabilities from the GPU is this:
> 
> - UBO Maximum Block Size = 65536
> - UBO Buffer Offset Alignment = 4
> 
> So the maximum size used by the application is 65536 bytes.
> 
> UBOs are used as shared buffers so blocks of data are placed next to each
> other respecting alignment and updated.
> 
> UBOs are created like this:
> 
> glBindBuffer(GL_UNIFORM_BUFFER, pUBO)  // <= done once
> glBufferData(GL_UNIFORM_BUFFER, bufferSize, NULL, GL_DYNAMIC_DRAW)  // <=
> done once
> glMapBufferRange(GL_UNIFORM_BUFFER, stride * elementCount, elementStride,
> GL_WRITE_ONLY | GL_MAP_INVALIDATE_RANGE_BIT)  // <= done for each data block
> written
> 
> Data then written and unmapped
> 
> In particular this means a larger UBO is created once then individual blocks
> are written to it using ranged mapping. Just a wield guess but could the
> problem be related to this kind of usage pattern?

UBOs are written to the shader cache, and shade cache items are kept in memory
in a queue when all threads are busy compiling. If you have large UBOs this
could indeed be your problem.

The following merge request might be helpful. Are you able to give this a test?

https://gitlab.freedesktop.org/mesa/mesa/merge_requests/1852

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