[Mesa-dev] [PATCH v3 6/6] gallium/docs - add OpenSWR documentation
Tim Rowley
timothy.o.rowley at intel.com
Thu Feb 25 03:20:23 UTC 2016
---
src/gallium/docs/source/drivers/openswr.rst | 21 +++
src/gallium/docs/source/drivers/openswr/faq.rst | 141 +++++++++++++++++++++
src/gallium/docs/source/drivers/openswr/knobs.rst | 114 +++++++++++++++++
.../docs/source/drivers/openswr/profiling.rst | 67 ++++++++++
src/gallium/docs/source/drivers/openswr/usage.rst | 38 ++++++
5 files changed, 381 insertions(+)
create mode 100644 src/gallium/docs/source/drivers/openswr.rst
create mode 100644 src/gallium/docs/source/drivers/openswr/faq.rst
create mode 100644 src/gallium/docs/source/drivers/openswr/knobs.rst
create mode 100644 src/gallium/docs/source/drivers/openswr/profiling.rst
create mode 100644 src/gallium/docs/source/drivers/openswr/usage.rst
diff --git a/src/gallium/docs/source/drivers/openswr.rst b/src/gallium/docs/source/drivers/openswr.rst
new file mode 100644
index 0000000..84aa51f
--- /dev/null
+++ b/src/gallium/docs/source/drivers/openswr.rst
@@ -0,0 +1,21 @@
+OpenSWR
+=======
+
+The Gallium OpenSWR driver is a high performance, highly scalable
+software renderer targeted towards visualization workloads. For such
+geometry heavy workloads there is a considerable speedup over llvmpipe,
+which is to be expected as the geometry frontend of llvmpipe is single
+threaded.
+
+This rasterizer is x86 specific and requires AVX or AVX2. The driver
+fits into the gallium framework, and reuses gallivm for doing the TGSI
+to vectorized llvm-IR conversion of the shader kernels.
+
+.. toctree::
+ :glob:
+
+ openswr/usage
+ openswr/faq
+ openswr/profiling
+ openswr/knobs
+
diff --git a/src/gallium/docs/source/drivers/openswr/faq.rst b/src/gallium/docs/source/drivers/openswr/faq.rst
new file mode 100644
index 0000000..596d77f
--- /dev/null
+++ b/src/gallium/docs/source/drivers/openswr/faq.rst
@@ -0,0 +1,141 @@
+FAQ
+===
+
+Why another software rasterizer?
+--------------------------------
+
+Good question, given there are already three (swrast, softpipe,
+llvmpipe) in the Mesa3D tree. Two important reasons for this:
+
+ * Architecture - given our focus on scientific visualization, our
+ workloads are much different than the typical game; we have heavy
+ vertex load and relatively simple shaders. In addition, the core
+ counts of machines we run on are much higher. These parameters led
+ to design decisions much different than llvmpipe.
+
+ * Historical - Intel had developed a high performance software
+ graphics stack for internal purposes. Later we adapted this
+ graphics stack for use in visualization and decided to move forward
+ with Mesa3D to provide a high quality API layer while at the same
+ time benefiting from the excellent performance the software
+ rasterizerizer gives us.
+
+What's the architecture?
+------------------------
+
+SWR is a tile based immediate mode renderer with a sort-free threading
+model which is arranged as a ring of queues. Each entry in the ring
+represents a draw context that contains all of the draw state and work
+queues. An API thread sets up each draw context and worker threads
+will execute both the frontend (vertex/geometry processing) and
+backend (fragment) work as required. The ring allows for backend
+threads to pull work in order. Large draws are split into chunks to
+allow vertex processing to happen in parallel, with the backend work
+pickup preserving draw ordering.
+
+Our pipeline uses just-in-time compiled code for the fetch shader that
+does vertex attribute gathering and AOS to SOA conversions, the vertex
+shader and fragment shaders, streamout, and fragment blending. SWR
+core also supports geometry and compute shaders but we haven't exposed
+them through our driver yet. The fetch shader, streamout, and blend is
+built internally to swr core using LLVM directly, while for the vertex
+and pixel shaders we reuse bits of llvmpipe from
+``gallium/auxiliary/gallivm`` to build the kernels, which we wrap
+differently than llvmpipe's ``auxiliary/draw`` code.
+
+What's the performance?
+-----------------------
+
+For the types of high-geometry workloads we're interested in, we are
+significantly faster than llvmpipe. This is to be expected, as
+llvmpipe only threads the fragment processing and not the geometry
+frontend. The performance advantage over llvmpipe roughly scales
+linearly with the number of cores available.
+
+While our current performance is quite good, we know there is more
+potential in this architecture. When we switched from a prototype
+OpenGL driver to Mesa we regressed performance severely, some due to
+interface issues that need tuning, some differences in shader code
+generation, and some due to conformance and feature additions to the
+core swr. We are looking to recovering most of this performance back.
+
+What's the conformance?
+-----------------------
+
+The major applications we are targeting are all based on the
+Visualization Toolkit (VTK), and as such our development efforts have
+been focused on making sure these work as best as possible. Our
+current code passes vtk's rendering tests with their new "OpenGL2"
+(really OpenGL 3.2) backend at 99%.
+
+piglit testing shows a much lower pass rate, roughly 80% at the time
+of writing. Core SWR undergoes rigorous unit testing and we are quite
+confident in the rasterizer, and understand the areas where it
+currently has issues (example: line rendering is done with triangles,
+so doesn't match the strict line rendering rules). The majority of
+the piglit failures are errors in our driver layer interfacing Mesa
+and SWR. Fixing these issues is one of our major future development
+goals.
+
+Why are you open sourcing this?
+-------------------------------
+
+ * Our customers prefer open source, and allowing them to simply
+ download the Mesa source and enable our driver makes life much
+ easier for them.
+
+ * The internal gallium APIs are not stable, so we'd like our driver
+ to be visible for changes.
+
+ * It's easier to work with the Mesa community when the source we're
+ working with can be used as reference.
+
+What are your development plans?
+--------------------------------
+
+ * Performance - see the performance section earlier for details.
+
+ * Conformance - see the conformance section earlier for details.
+
+ * Features - core SWR has a lot of functionality we have yet to
+ expose through our driver, such as MSAA, geometry shaders, compute
+ shaders, and tesselation.
+
+ * AVX512 support
+
+What is the licensing of the code?
+----------------------------------
+
+ * All code is under the normal Mesa MIT license.
+
+Will this work on AMD?
+----------------------
+
+ * If using an AMD processor with AVX or AVX2, it should work though
+ we don't have that hardware around to test. Patches if needed
+ would be welcome.
+
+Will this work on ARM, MIPS, POWER, <other non-x86 architecture>?
+-------------------------------------------------------------------------
+
+ * Not without a lot of work. We make extensive use of AVX and AVX2
+ intrinsics in our code and the in-tree JIT creation. It is not the
+ intention for this codebase to support non-x86 architectures.
+
+What hardware do I need?
+------------------------
+
+ * Any x86 processor with at least AVX (introduced in the Intel
+ SandyBridge and AMD Bulldozer microarchitectures in 2011) will
+ work.
+
+ * You don't need a fire-breathing Xeon machine to work on SWR - we do
+ day-to-day development with laptops and desktop CPUs.
+
+Does one build work on both AVX and AVX2?
+-----------------------------------------
+
+Yes. The build system creates two shared libraries, ``libswrAVX.so`` and
+``libswrAVX2.so``, and ``swr_create_screen()`` loads the appropriate one at
+runtime.
+
diff --git a/src/gallium/docs/source/drivers/openswr/knobs.rst b/src/gallium/docs/source/drivers/openswr/knobs.rst
new file mode 100644
index 0000000..06f228a
--- /dev/null
+++ b/src/gallium/docs/source/drivers/openswr/knobs.rst
@@ -0,0 +1,114 @@
+Knobs
+=====
+
+OpenSWR has a number of environment variables which control its
+operation, in addition to the normal Mesa and gallium controls.
+
+.. envvar:: KNOB_ENABLE_ASSERT_DIALOGS <bool> (true)
+
+Use dialogs when asserts fire. Asserts are only enabled in debug builds
+
+.. envvar:: KNOB_SINGLE_THREADED <bool> (false)
+
+If enabled will perform all rendering on the API thread. This is useful mainly for debugging purposes.
+
+.. envvar:: KNOB_DUMP_SHADER_IR <bool> (false)
+
+Dumps shader LLVM IR at various stages of jit compilation.
+
+.. envvar:: KNOB_USE_GENERIC_STORETILE <bool> (false)
+
+Always use generic function for performing StoreTile. Will be slightly slower than using optimized (jitted) path
+
+.. envvar:: KNOB_FAST_CLEAR <bool> (true)
+
+Replace 3D primitive execute with a SWRClearRT operation and defer clear execution to first backend op on hottile, or hottile store
+
+.. envvar:: KNOB_MAX_NUMA_NODES <uint32_t> (0)
+
+Maximum # of NUMA-nodes per system used for worker threads 0 == ALL NUMA-nodes in the system N == Use at most N NUMA-nodes for rendering
+
+.. envvar:: KNOB_MAX_CORES_PER_NUMA_NODE <uint32_t> (0)
+
+Maximum # of cores per NUMA-node used for worker threads. 0 == ALL non-API thread cores per NUMA-node N == Use at most N cores per NUMA-node
+
+.. envvar:: KNOB_MAX_THREADS_PER_CORE <uint32_t> (1)
+
+Maximum # of (hyper)threads per physical core used for worker threads. 0 == ALL hyper-threads per core N == Use at most N hyper-threads per physical core
+
+.. envvar:: KNOB_MAX_WORKER_THREADS <uint32_t> (0)
+
+Maximum worker threads to spawn. IMPORTANT: If this is non-zero, no worker threads will be bound to specific HW threads. They will all be "floating" SW threads. In this case, the above 3 KNOBS will be ignored.
+
+.. envvar:: KNOB_BUCKETS_START_FRAME <uint32_t> (1200)
+
+Frame from when to start saving buckets data. NOTE: KNOB_ENABLE_RDTSC must be enabled in core/knobs.h for this to have an effect.
+
+.. envvar:: KNOB_BUCKETS_END_FRAME <uint32_t> (1400)
+
+Frame at which to stop saving buckets data. NOTE: KNOB_ENABLE_RDTSC must be enabled in core/knobs.h for this to have an effect.
+
+.. envvar:: KNOB_WORKER_SPIN_LOOP_COUNT <uint32_t> (5000)
+
+Number of spin-loop iterations worker threads will perform before going to sleep when waiting for work
+
+.. envvar:: KNOB_MAX_DRAWS_IN_FLIGHT <uint32_t> (160)
+
+Maximum number of draws outstanding before API thread blocks.
+
+.. envvar:: KNOB_MAX_PRIMS_PER_DRAW <uint32_t> (2040)
+
+Maximum primitives in a single Draw(). Larger primitives are split into smaller Draw calls. Should be a multiple of (3 * vectorWidth).
+
+.. envvar:: KNOB_MAX_TESS_PRIMS_PER_DRAW <uint32_t> (16)
+
+Maximum primitives in a single Draw() with tessellation enabled. Larger primitives are split into smaller Draw calls. Should be a multiple of (vectorWidth).
+
+.. envvar:: KNOB_MAX_FRAC_ODD_TESS_FACTOR <float> (63.0f)
+
+(DEBUG) Maximum tessellation factor for fractional-odd partitioning.
+
+.. envvar:: KNOB_MAX_FRAC_EVEN_TESS_FACTOR <float> (64.0f)
+
+(DEBUG) Maximum tessellation factor for fractional-even partitioning.
+
+.. envvar:: KNOB_MAX_INTEGER_TESS_FACTOR <uint32_t> (64)
+
+(DEBUG) Maximum tessellation factor for integer partitioning.
+
+.. envvar:: KNOB_BUCKETS_ENABLE_THREADVIZ <bool> (false)
+
+Enable threadviz output.
+
+.. envvar:: KNOB_TOSS_DRAW <bool> (false)
+
+Disable per-draw/dispatch execution
+
+.. envvar:: KNOB_TOSS_QUEUE_FE <bool> (false)
+
+Stop per-draw execution at worker FE NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_FETCH <bool> (false)
+
+Stop per-draw execution at vertex fetch NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_IA <bool> (false)
+
+Stop per-draw execution at input assembler NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_VS <bool> (false)
+
+Stop per-draw execution at vertex shader NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_SETUP_TRIS <bool> (false)
+
+Stop per-draw execution at primitive setup NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_BIN_TRIS <bool> (false)
+
+Stop per-draw execution at primitive binning NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
+.. envvar:: KNOB_TOSS_RS <bool> (false)
+
+Stop per-draw execution at rasterizer NOTE: Requires KNOB_ENABLE_TOSS_POINTS to be enabled in core/knobs.h
+
diff --git a/src/gallium/docs/source/drivers/openswr/profiling.rst b/src/gallium/docs/source/drivers/openswr/profiling.rst
new file mode 100644
index 0000000..357754c
--- /dev/null
+++ b/src/gallium/docs/source/drivers/openswr/profiling.rst
@@ -0,0 +1,67 @@
+Profiling
+=========
+
+OpenSWR contains built-in profiling which can be enabled
+at build time to provide insight into performance tuning.
+
+To enable this, uncomment the following line in ``rasterizer/core/knobs.h`` and rebuild: ::
+
+ //#define KNOB_ENABLE_RDTSC
+
+Running an application will result in a ``rdtsc.txt`` file being
+created in current working directory. This file contains profile
+information captured between the ``KNOB_BUCKETS_START_FRAME`` and
+``KNOB_BUCKETS_END_FRAME`` (see knobs section).
+
+The resulting file will contain sections for each thread with a
+hierarchical breakdown of the time spent in the various operations.
+For example: ::
+
+ Thread 0 (API)
+ %Tot %Par Cycles CPE NumEvent CPE2 NumEvent2 Bucket
+ 0.00 0.00 28370 2837 10 0 0 APIClearRenderTarget
+ 0.00 41.23 11698 1169 10 0 0 |-> APIDrawWakeAllThreads
+ 0.00 18.34 5202 520 10 0 0 |-> APIGetDrawContext
+ 98.72 98.72 12413773688 29957 414380 0 0 APIDraw
+ 0.36 0.36 44689364 107 414380 0 0 |-> APIDrawWakeAllThreads
+ 96.36 97.62 12117951562 9747 1243140 0 0 |-> APIGetDrawContext
+ 0.00 0.00 19904 995 20 0 0 APIStoreTiles
+ 0.00 7.88 1568 78 20 0 0 |-> APIDrawWakeAllThreads
+ 0.00 25.28 5032 251 20 0 0 |-> APIGetDrawContext
+ 1.28 1.28 161344902 64 2486370 0 0 APIGetDrawContext
+ 0.00 0.00 50368 2518 20 0 0 APISync
+ 0.00 2.70 1360 68 20 0 0 |-> APIDrawWakeAllThreads
+ 0.00 65.27 32876 1643 20 0 0 |-> APIGetDrawContext
+
+
+ Thread 1 (WORKER)
+ %Tot %Par Cycles CPE NumEvent CPE2 NumEvent2 Bucket
+ 83.92 83.92 13198987522 96411 136902 0 0 FEProcessDraw
+ 24.91 29.69 3918184840 167 23410158 0 0 |-> FEFetchShader
+ 11.17 13.31 1756972646 75 23410158 0 0 |-> FEVertexShader
+ 8.89 10.59 1397902996 59 23410161 0 0 |-> FEPAAssemble
+ 19.06 22.71 2997794710 384 7803387 0 0 |-> FEClipTriangles
+ 11.67 61.21 1834958176 235 7803387 0 0 |-> FEBinTriangles
+ 0.00 0.00 0 0 187258 0 0 |-> FECullZeroAreaAndBackface
+ 0.00 0.00 0 0 60051033 0 0 |-> FECullBetweenCenters
+ 0.11 0.11 17217556 2869592 6 0 0 FEProcessStoreTiles
+ 15.97 15.97 2511392576 73665 34092 0 0 WorkerWorkOnFifoBE
+ 14.04 87.95 2208687340 9187 240408 0 0 |-> WorkerFoundWork
+ 0.06 0.43 9390536 13263 708 0 0 |-> BELoadTiles
+ 0.00 0.01 293020 182 1609 0 0 |-> BEClear
+ 12.63 89.94 1986508990 949 2093014 0 0 |-> BERasterizeTriangle
+ 2.37 18.75 372374596 177 2093014 0 0 |-> BETriangleSetup
+ 0.42 3.35 66539016 31 2093014 0 0 |-> BEStepSetup
+ 0.00 0.00 0 0 21766 0 0 |-> BETrivialReject
+ 1.05 8.33 165410662 79 2071248 0 0 |-> BERasterizePartial
+ 6.06 48.02 953847796 1260 756783 0 0 |-> BEPixelBackend
+ 0.20 3.30 31521202 41 756783 0 0 |-> BESetup
+ 0.16 2.69 25624304 33 756783 0 0 |-> BEBarycentric
+ 0.18 2.92 27884986 36 756783 0 0 |-> BEEarlyDepthTest
+ 0.19 3.20 30564174 41 744058 0 0 |-> BEPixelShader
+ 0.26 4.30 41058646 55 744058 0 0 |-> BEOutputMerger
+ 1.27 20.94 199750822 32 6054264 0 0 |-> BEEndTile
+ 0.33 2.34 51758160 23687 2185 0 0 |-> BEStoreTiles
+ 0.20 60.22 31169500 28807 1082 0 0 |-> B8G8R8A8_UNORM
+ 0.00 0.00 302752 302752 1 0 0 WorkerWaitForThreadEvent
+
diff --git a/src/gallium/docs/source/drivers/openswr/usage.rst b/src/gallium/docs/source/drivers/openswr/usage.rst
new file mode 100644
index 0000000..e55b421
--- /dev/null
+++ b/src/gallium/docs/source/drivers/openswr/usage.rst
@@ -0,0 +1,38 @@
+Usage
+=====
+
+Requirements
+^^^^^^^^^^^^
+
+* An x86 processor with AVX or AVX2
+* LLVM version 3.6 or later
+
+Building
+^^^^^^^^
+
+To build with GNU automake, select building the swr driver at
+configure time, for example: ::
+
+ configure --with-gallium-drivers=swrast,swr
+
+Using
+^^^^^
+
+On Linux, building will create a drop-in alternative for libGL.so into::
+
+ lib/gallium/libGL.so
+
+or::
+
+ build/foo/gallium/targets/libgl-xlib/libGL.so
+
+To use it set the LD_LIBRARY_PATH environment variable accordingly.
+
+**IMPORTANT:** Mesa will default to using llvmpipe or softpipe as the default software renderer. To select the OpenSWR driver, set the GALLIUM_DRIVER environment variable appropriately: ::
+
+ GALLIUM_DRIVER=swr
+
+To verify OpenSWR is being used, check to see if a message like the following is printed when the application is started: ::
+
+ SWR detected AVX2
+
--
1.9.1
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