[Mesa-dev] [Bug 111043] PBO unpacking is not accelerated

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=111043

            Bug ID: 111043
           Summary: PBO unpacking is not accelerated
           Product: Mesa
           Version: git
          Hardware: x86-64 (AMD64)
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Mesa core
          Assignee: mesa-dev at lists.freedesktop.org
          Reporter: malcolmjestadt at gmail.com
        QA Contact: mesa-dev at lists.freedesktop.org

While investigating performance bottlenecks with RPCS3 while using Radeonsi, I
came across a scene which was only getting 1FPS, while spending 99% of the CPU
time in the driver. Further investigation led to the discovery that using the
GL_STREAM_COPY flag instead of GL_STATIC_COPY led to performance increasing to
11fps. 

This prompted us to look into Mesa's code for an explanation, since the
operation here should be moving data between GPU memory to GPU memory, and
shouldn't be faster with GL_STREAM_COPY. 

We came across this
https://gitlab.freedesktop.org/mesa/mesa/commit/a338dc01866ce50bf7555ee8dc08491c7f63b585
which provided an explanation for why GL_STREAM_COPY was faster. 

Anyways, point is we need PBO unpacking acceleration for this to be any faster.
Even when using the GL_STREAM_COPY flag about 90% of the time spent in the
graphics thread is spent in a single function in the driver. 

Thanks.

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