Paul Berry
f2f14bc4a9
Although there is not much documentation of this fact, there are in
fact two separate VF caches:
- an "index-based" cache (described in the Sandy Bridge PRM, vol 2
part 1, section 2.1.2 "Vertex Cache"). This cache stores URB
handles of vertex shader outputs; its purpose is to avoid redundant
invocations of the vertex shader when drawing in random access mode
(e.g. glDrawElements()), and the same vertex index is specified
multiple times. It is automatically invalidated between
3D_PRIMITIVE commands and between instances within a single
3D_PRIMITIVE command.
- an "address-based" cache (mentioned briefly in vol 2 part 1, section
1.7.4 "PIPE_CONTROL Command"). This cache stores the data read from
vertex buffers; its purpose is to avoid redundant memory accesses
when doing instanced drawing or when multiple 3D_PRIMITIVE commands
access the same vertex data. It needs to be manually invalidated
whenever new data is written to a buffer that is used for vertex
data.
Previous to this patch, it was not necessary for Mesa to explicitly
invalidate the address-based cache, because there were no reasonable
use cases in which the GPU would write to a vertex data buffer during
a batch, and inter-batch flushing was taken care of by the kernel.
However, with transform feedback, there is now a reasonable use case:
vertex data is written to a buffer using transform feedback, and then
that data is immediately re-used as vertex input in the next drawing
operation. To make this use case work, we need to flush the
address-based VF cache between transform feedback and the next draw
operation. Since we are already calling
intel_batchbuffer_emit_mi_flush() when transform feedback completes,
and intel_batchbuffer_emit_mi_flush() is intended to invalidate all
caches, it seems reasonable to add VF cache invalidation to this
function.
As with commit 63cf7fad13 (i965: Flush
pipeline on EndTransformFeedback), this is not an ideal solution. It
would be preferable to only invalidate the VF cache if the next draw
call was about to consume data generated by a previous draw call in
the same batch. However, since we don't have the necessary dependency
tracking infrastructure to figure that out right now, we have to
overzealously invalidate the cache.
Fixes Piglit test "EXT_transform_feedback/immediate-reuse".
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
File: docs/README.WIN32 Last updated: 23 April 2011 Quick Start ----- ----- Windows drivers are build with SCons. Makefiles or Visual Studio projects are no longer shipped or supported. Run scons osmesa mesagdi to build classic mesa Windows GDI drivers; or scons libgl-gdi to build gallium based GDI driver. This will work both with MSVS or Mingw. Windows Drivers ------- ------- At this time, only the gallium GDI driver is known to work. Source code also exists in the tree for other drivers in src/mesa/drivers/windows, but the status of this code is unknown. General ------- After building, you can copy the above DLL files to a place in your PATH such as $SystemRoot/SYSTEM32. If you don't like putting things in a system directory, place them in the same directory as the executable(s). Be careful about accidentially overwriting files of the same name in the SYSTEM32 directory. The DLL files are built so that the external entry points use the stdcall calling convention. Static LIB files are not built. The LIB files that are built with are the linker import files associated with the DLL files. The si-glu sources are used to build the GLU libs. This was done mainly to get the better tessellator code. If you have a Windows-related build problem or question, please post to the mesa-dev or mesa-users list.