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Merge pull request #9766 from stenzek/ogl-bbox-memory-barrier 

OGL: Force memory barrier when reading back bounding box values
This commit is contained in:
Connor McLaughlin 2021-05-29 17:04:57 +10:00 committed by GitHub
parent b31d4400e3 6393f157f0
commit b3a414ea9d
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 12 additions and 3 deletions
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15
Source/Core/VideoBackends/OGL/OGLBoundingBox.cpp
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@ -87,12 +87,21 @@ void BoundingBox::Flush()
void BoundingBox::Readback()
{
glBindBuffer(GL_SHADER_STORAGE_BUFFER, s_bbox_buffer_id);
// Using glMapBufferRange to read back the contents of the SSBO is extremely slow
// on nVidia drivers. This is more noticeable at higher internal resolutions.
// Using glGetBufferSubData instead does not seem to exhibit this slowdown.
if (!DriverDetails::HasBug(DriverDetails::BUG_SLOW_GETBUFFERSUBDATA) &&
!static_cast<Renderer*>(g_renderer.get())->IsGLES())
{
// Using glMapBufferRange to read back the contents of the SSBO is extremely slow
// on nVidia drivers. This is more noticeable at higher internal resolutions.
// Using glGetBufferSubData instead does not seem to exhibit this slowdown.
// We also need to ensure the the CPU does not receive stale values which have been updated by
// the GPU. Apparently the buffer here is not coherent on NVIDIA drivers. Not sure if this is a
// driver bug/spec violation or not, one would think that glGetBufferSubData() would invalidate
// any caches as needed, but this path is only used on NVIDIA anyway, so it's fine. A point to
// note is that according to ARB_debug_report, it's moved from video to host memory, which would
// explain why it needs the cache invalidate.
glMemoryBarrier(GL_SHADER_STORAGE_BARRIER_BIT);
std::array<s32, NUM_BBOX_VALUES> gpu_values;
glGetBufferSubData(GL_SHADER_STORAGE_BUFFER, 0, sizeof(s32) * NUM_BBOX_VALUES,
gpu_values.data());