intelReadPixels: fallback to CPU mapping in PBO case for Z24S8 attachments
Submitted by Markus Wick
Assigned to Intel 3D Bugs Mailing List
Created attachment 139997 Apitrace dump of citra showing the performance issue
calling glReadPixels for the GL_DEPTH24_STENCIL8 attachment and the GL_DEPTH_STENCIL / GL_UNSIGNED_INT_24_8 format seems to stall the GPU, even if a PBO is bound. 92% of my CPU time is spend in intel_miptree_map.
I guess i965 lacks a copy shader for the tiled Z24S8 attachment to the linear TBO buffer.
Tests was done on: Mesa DRI Intel(R) UHD Graphics 620 (Kabylake GT2) and mesa: 4affeba1
An apitrace dump which highlights this issue in the last frames is attached.
Attachment 139997, "Apitrace dump of citra showing the performance issue":