Learn how NVIDIA continues improving both Vulkan and OpenGL for cross-platform graphics and compute development. This high-level talk is intended for anyone wanting to understand the state of Vulkan and OpenGL in 2017 on NVIDIA GPUs. For OpenGL, the latest standard update maintains the compatibility and feature-richness you expect. For Vulkan, NVIDIA has enabled the latest NVIDIA GPU hardware features and now provides explicit support for multiple GPUs. And for either API, NVIDIA's SDKs and Nsight tools help you develop and debug your application faster. NVIDIA booth theater presentation at SIGGRAPH in Los Angeles, August 1, 2017. http://www.nvidia.com/object/siggraph2017-schedule.html?id=sig1732 Get your SIGGRAPH driver release with OpenGL 4.6 and the latest Vulkan functionality from https://developer.nvidia.com/opengl-driver

1. Mark Kilgard, August 1
SIGGRAPH 2017, Los Angeles
NVIDIA OpenGL and Vulkan
Support in 2017

2. 2
Mark Kilgard
• Principal System Software Engineer
OpenGL driver and API evolution
Cg (“C for graphics”) shading language
GPU-accelerated path rendering & web browser
rendering
• OpenGL Utility Toolkit (GLUT) implementer
• Specified and implemented much of OpenGL
• Author of OpenGL for the X Window System
• Co-author of Cg Tutorial
• Worked on OpenGL for over 25 years
My Background

3. 3
Focus

4. 4
Focus
1.0 + extensions4.6 + extensions

5. 5
Khronos announces OpenGL 4.6 with SPIR-V support Monday

6. 6
NVIDIA posts OpenGL 4.6 the same day

7. 7
NVIDIA’s OpenGL Leverage
Debugging with
Nsight
Programmable
Graphics
Android & SHIELD
Quadro
OptiX
GeForce
Adobe Creative Cloud
Embedded Projects

8. 8
OpenGL Codebase Leverage
Same driver code base supports multiple APIs
OpenGL for Embedded,
Mobile, and Web
Multi-vendor, explicit, low-level graphics
from Khronos

9. 9
NVIDIA’s Shading Compiler Even More Leveraged
Various
Direct3D versions3D APIs based on NVIDIA OpenGL driver code base
NVIDIA Shading Compiler code base
Apple’s proprietary
graphics API
Proprietary console API

10. 10
For those tracking birthdays...
Then celebrating OpenGL 4.3 Now celebrating OpenGL 4.6

11. 11
Introducing OpenGL 4.6
• Big feature: SPIR-V support required
• SPIR-V = standard intermediate language for parallel compute and graphics
• Vulkan 1.0 standard requires expressing SPIR-V
• Allows content creators to simplify their shader authoring and management pipelines
• Previously this was an optional ARB extension, not required for 4.5
• Includes NEW ARB_spirv_extensions to SPIR-V support
• Genius of AND: OpenGL 4.6 allows either GLSL or SPIR-V, your choice
• Technically, NVIDIA’s Vulkan 1.0 allows use GLSL directly via an extension
• Additional new ARB extensions bundled in OpenGL 4.6 for
• Improving performance
• Improving rendering quality
• Resolving outstanding Intellectual Property (IP) issues
support built-in

12. 12
What OpenGL 4.6 Packages Together
• OpenGL evolves by bundling extensions as a core version update
• OpenGL 4.6 = everything in 4.5 plus these extensions
• ARB_indirect_parameters
• ARB_pipeline_statistics_query
• ARB_polygon_offset_clamp
• KHR_no_error
• ARB_shader_atomic_counter_ops (just extends OpenGL Shading Language)
• ARB_shader_draw_parameters
• ARB_shader_group_vote (just extends OpenGL Shading Language)
• ARB_gl_spirv
• ARB_spirv_extensions
• ARB_texture_filter_anisotropic
• ARB_transform_feedback_overflow_query
• Now you can code for this functionality without ARB or EXT suffixing!
Technically the one “brand new” extension;
other 4.6 functionality already proven & public

13. 13
OpenGL extension exposing Khronos intermediate
language for parallel compute and graphics
Khronos extension for OpenGL + SPIR-V
ARB extension announced last year
July 22, 2016
Allows compiled SPIR-V code to be passed directly to OpenGL driver
Accepts SPIR-V output from open source Glslang Khronos Reference compiler
https://github.com/KhronosGroup/glslang
Other compilers can target SPIR-V too
Khronos standard extension ARB_gl_spirv
+

14. 14
SPIR-V Ecosystem
LLVM
Third party kernel and
shader Languages
•SPIR-V
•Khronos defined and controlled
cross-API intermediate language
•Native support for graphics
and parallel constructs
•32-bit Word Stream
•Extensible and easily parsed
•Retains data object and control
flow information for effective
code generation and translation
OpenCL C++OpenCL C
GLSL
Khronos has open sourced
these tools and translators
IHV Driver
Runtimes
Other
Intermediate
Forms
SPIR-V Validator
SPIR-V (Dis)Assembler LLVM to SPIR-V
Bi-directional
Translator
Khronos plans to open
source these tools soon
https://github.com/KhronosGroup/SPIR/tree/spirv-1.1
Open source C++
front-end released
HLSL
Khronos has open sourced
these tools and translators
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators HLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
OpenCL C
GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
OpenCL C++OpenCL C
GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
LLVM to SPIR-V
Bi-directional
Translator
OpenCL C++OpenCL C
GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
SPIR-V Validator
LLVM to SPIR-V
Bi-directional
Translator
OpenCL C++OpenCL C
GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
SPIR-V (Dis)Assembler
SPIR-V Validator
LLVM to SPIR-V
Bi-directional
Translator
OpenCL C++OpenCL C
GLSLHLSL
Khronos plans to open
source these tools soon
Khronos has open sourced
these tools and translators
OpenGL support NEW with
ARB_gl_spirv
Standard in
OpenGL 4.6

15. 15
ARB_gl_spirv
•This extension announced SIGGRAPH 2016
• But was optional
• NVIDIA’s SIGGRAPH driver last year immediately provided support
•Much more useful to have core part of OpenGL 4.6
•And NOW it is!

16. 16
Driver
Pre-OpenGL 4.6
GLSL Compilation of Text Based Shaders
shader.vert
shader.geom
shader.frag
GPU
GLSL Compiler
Front-end
GPU-specific
Compiler
Back-end
your run-time process hardware
your
app

17. 17
Driver
your
app GLSL Compiler
Front-end
OpenGL 4.6
Offline Compilation of GLSL to SPIR-V
GPU
shader.vert
shader.geom
shader.frag
shader.vert.spv
shader.geom.pv
shader.frag.spv
glslangValidator
or
glslc
GPU-specific
Compiler
Back-end
SPIR-V
Compiler
Front-end
your run-time processbuild-time compilation hardware

18. 18
Use OpenGL 4.6 SPIR-V Support
as Your Bridge to Vulkan
• Thinking about Vulkan? Realizing it’s a major, involved transition?
• Consider making your transition in steps
• First transition GLSL text shaders to SPIR-V binary shaders with OpenGL 4.6
• Then move to Vulkan API

19. 19
Driver
your
app GLSL Compiler
Front-end
OpenGL 4.6 Transition to
Offline Compilation of GLSL to SPIR-V
GPU
shader.vert
shader.geom
shader.frag
shader.vert.spv
shader.geom.pv
shader.frag.spv
glslangValidator
or
glslc
GPU-specific
Compiler
Back-end
SPIR-V
Compiler
Front-end
your run-time processbuild-time compilation hardware

20. 20
Driver
Vulkan
Offline Compilation of GLSL to SPIR-V
your
app
GPU
shader.vert
shader.geom
shader.frag
shader.vert.spv
shader.geom.pv
shader.frag.spv
glslangValidator
or
glslc
GPU-specific
Compiler
Back-end
SPIR-V
Compiler
Front-end
your run-time processbuild-time compilation hardware

21. 21
API Usage Differences: Compiling GLSL vs. SPIR-V
glCreateProgram
glShaderSource
glCompileShader
glAttachShader
glCreateShader
glLinkProgram
glGetUniformLocation
glGetAttribLocation
Read GLSL text from file
glUseProgram
glProgramUniform*
while more
shader
domains while more
uniforms
to introspect
while more
attributes
to introspect
pre-4.6

22. 22
API Usage Differences: Compiling GLSL vs. SPIR-V
glCreateProgram
glShaderBinary
glSpecializeShader
glAttachShader
glCreateShader
glLinkProgram
Read SPIR-V binary blob from file
glUseProgram
glProgramUniform*
while more
shader
domains
while more
uniforms
to initialize
app assume locations
assigned within the shader,
obviating dynamic introspection
4.6 or ARB_gl_spirv

23. 23
ARB_spirv_extensions
• Only extension rolled into OpenGL 4.6 that is truly new
• Motivation
• Lots of established OpenGL extensions have accompanying GLSL support
• Example: extension adds new GLSL functions
• 2016 version of SPIR-V just supported GLSL functionality of core OpenGL 4.5
• ARB_spirv_extensions to the rescue!
• Provides a list of SPIR-V extensions
• Such extensions indicate SPIR-V support available for one (or more) OpenGL extensions
requiring GLSL support

24. 24
NVIDIA Provides Complete SPIR-V Extensions
SPIR-V Extension Name Corresponding OpenGL extension or
functionality
NVIDIA
Support
SPV_KHR_shader_ballot ARB_shader_ballot
SPV_KHR_shader_draw_parameters ARB_shader_draw_parameters
SPV_KHR_subgroup_vote ARB_shader_group_vote
SPV_NV_stereo_view_rendering NV_stereo_view_rendering
SPV_NV_viewport_array2 NV_viewport_array2 or
ARB_shader_viewport_layer_array
SPV_NV_geometry_shader_passthrough NV_geometry_shader_passthrough
SPV_NV_sample_mask_override_coverage NV_sample_mask_override_coverage
SPV_KHR_shader_atomic_counter_ops ARB_shader_atomic_counter_ops
SPV_KHR_post_depth_coverage ARB_post_depth_coverage
SPV_KHR_storage_buffer_storage_class Storage buffer support

25. 25
OpenGL 4.6 Fully Realizes “AZDO” Vision
AZDO = Approaching Zero Driver Overhead
Culmination of a multi-year effort to integrate a succession extensions into
core OpenGL for minimizing OpenGL driver head is now complete
ARB_indirect_parameters & ARB_shader_draw_parameters now core in OpenGL 4.6

26. 26
OpenGL 4.6 Adds More
“Approaching Zero Driver Overhead” (AZDO)
Goodness
Frustrated GPU due to slow feeding from the CPU Happy confident GPU feeding herself
ARB_indirect_parameters & ARB_shader_draw_parameters now core in OpenGL 4.6
Teach your GPU to feed itself with OpenGL 4.6’s multi draw indirect count

27. 27
OpenGL 4.6 Features for Better Rendering Quality
•Anisotropic texture filtering
• Improves texture filtering quality
• Intellectual Property (IP) issues resolved
• Compatible with existing multi-vendor
extension
•Polygon offset clamp
• Better control of depth bias
• Improve rendering quality for techniques
depending on polygon offset
Conventional
texture filtering
blurry in distance
Anisotropic
filtering
stays sharp in distance
silhouette
hidden surface
removal
co-planar geometry
improving shadow mapping

28. 28
Loose Ends Now Resolved in OpenGL 4.6
• ARB_shader_atomic_counter_ops — Atomic shader counter operations now complete
• ARB_shader_group_vote — Groups of graphics shaders can collectively vote
• Better performance through managing “herd behavior”
• KHR_no_error — Contexts can request driver skip error checks for performance
• ARB_transform_feedback_overflow_query
• GPU can report when streaming vertices overflows a transform feedback buffer
• ARB_pipeline_statistics_query — now pipeline statistic queries are standard
• GPU can now report crucial # of rendering operations performed

29. 29
Available Pipeline Query Statistics
Query token Queried statistic
GL_VERTICES_SUBMITTED # of vertices issued to OpenGL
GL_PRIMITIVES_SUBMITTED # of primitives issued to OpenGL
GL_VERTEX_SHADER_INVOCATIONS # of times a vertex shader invoked
GL_TESS_CONTROL_SHADER_PATCHES # of times a tessellation control shader invoked
GL_TESS_EVALUATION_SHADER_INVOCATIONS # of times a tessellation evaluation shader invoked
GL_GEOMETRY_SHADER_INVOCATIONS # of times a geometry shader invoked
GL_GEOMETRY_SHADER_PRIMITIVES_EMITTED # of primitives that entered primitive clipping
GL_FRAGMENT_SHADER_INVOCATIONS # of times a fragment shader invoked
GL_COMPUTE_SHADER_INVOCATIONS # of times a compute shader invoked
GL_CLIPPING_INPUT_PRIMITIVES # of primitives that entered primitive clipping
GL_CLIPPING_OUTPUT_PRIMITIVES # of primitives that output by primitive clipping

30. 30
Why OpenGL Core Updates
are Important (1)
• Not just opportunity for new functionality
• A new specification reconciles all the
bundled extensions into coherent single document
• Also lets OpenGL Working Group better structure OpenGL’s specification
• Future extensions can then be written against a cleanly resolved 4.6 specification
• Ensures new functionality is covered by the Khronos Intellectual Property (IP)
Framework
• OpenGL implementers, developers, and
end-users can confidently depend on the functionality described
• Specifically for 4.6, resolves Intellectual Property concerns for
both anisotropic texture filtering and polygon offset clamping
• Khronos maintains OpenGL, ES, and Vulkan in the
same “IP zone”—so ratifying a Khronos standard resolves issues
for related standards
Coherent Specification
Resolving IP Concerns

31. 31
Why OpenGL Core Updates
are Important (2)
•Not just opportunity for new functionality
•Opportunity to update Conformance
Test Suite (CTS)
• New tests obviously cover NEW functionality
• OpenGL 4.6 covers both NEW functionality + stricter
coverage of EXISTING functionality
•Developers adopt OpenGL features at different
levels of comfort
• Many developers are happy to use the latest, greatest
features as soon as extensions are shipped in drivers
• Other developers, often those with long-term support
horizons, look for core updates to signal mature
standards now ready to be adopted
Conformance Testing
QualitySheriff
Developer Comfort
Levels

32. 32
Why OpenGL Core Updates
are Important (3)
• Not just opportunity for new functionality
• OpenGL Shading Language (GLSL) gets accompanying revision
• So OpenGL 4.6 brings with it an updated GLSL
• Like the core API specification, the GLSL specification needs reconciliation of new
extensions, typos fixed, clarifications, etc.
• As many Vulkan applications express shaders in GLSL and compile them with glslang to
generate the SPIR-V that Vulkan expects, updating GLSL helps advance Vulkan
• OpenGL core revisions as much about consolidating OpenGL’s associated
ecosystem support as adding NEW features to OpenGL
Advancing the
Ecosystem

33. 33
OpenGL 4.6’s Resolving of IP Issues & New Open Sourcing of OpenGL
Conformance Suite Benefits Open Source OpenGL Implementation
• Khronos using Vulkan’s conformance approach for OpenGL now
• See https://github.com/KhronosGroup/VK-GL-CTS
• Should help Mesa keep closer to latest official standard, better for OpenGL overall
"OpenGL 4.6 will be the first OpenGL release where conformant open source
implementations based on the Mesa project will be deliverable in a reasonable
timeframe after release. The open sourcing of the OpenGL conformance test
suite and ongoing work between Khronos and X.org will also allow for non-vendor
led open source implementations to achieve conformance in the near future.“
David Airlie, senior principal engineer at Red Hat, and developer on Mesa /
X.org projects
Source: Khronos OpenGL 4.6 press release

34. 34
Credit for OpenGL 4.6
• Khronos relies on its member companies to complete new OpenGL core updates
• Different companies drove different features, all free to comment and contribute
• Reps of these companies primarily drove the constituent features of OpenGL 4.6
See Appendix J of OpenGL 4.6 for comprehensive list of contributor companies and individuals

35. 35
GLEW Support Available NOW
• GLEW = The OpenGL Extension Wrangler Library
Open source library
Pre-built distribution: http://glew.sourceforge.net/
Source code: https://github.com/nigels-com/glew
Your one-stop-shop for API support for all OpenGL extension APIs
• Now released GLEW 2.1 (July 31, 2017) provides complete API support for OpenGL 4.6
• Plus supports
Multi-vendor EXT interoperability extensions
All of NVIDIA’s Maxwell & Pascal extensions
All other NVIDIA multi-GPU generation initiatives
Examples: NV_path_rendering, NV_command_list, NV_gpu_multicast
Thanks to Nigel Stewart, GLEW maintainer, for this

36. 36
Miscellaneous NEW Extensions for 2017
• NV_blend_minmax_factor, based on AMD_blend_minmax_factor
• EXT_protected_textures (Tegra & ES only)
• Used with EGL’s EGL_EXT_protected_content
• Basis of Android 7.0’s secure texture video playback

37. 37
NVIDIA OpenGL in 2017 Provides
OpenGL’s Maximally Available Superset
OpenGL 4.6
Pascal
Extensions
2015 ARB extensions
OpenGL 4.5
Core
Maxwell
Extensions
Legacy EXT & Other
Compatibility Extensions
OpenGL Complete
Compatibility
Path Rendering
Multi-GPU.
SLI
Approaching Zero
Driver Overhead
NVIDIA Multi-generation
GPU Initiatives
DirectX inter-op
Vulkan inter-op
ES Enhancements
Full OpenGL
ES 3.2
Khronos Standard
Expected Compatibility
NVIDIA Initiatives
GPU Generation Features

38. 38
Open Source Efforts for Linux Graphics & OpenGL
from NVIDIA
•NVIDIA contributes to improve graphics support for entire Linux
ecosystem
•Examples
• GL Vendor-Neutral Dispatch (GLVND)
• arbitrates vendor-neutral access to OpenGL and EGL/GLX APIs
• Wayland support for EGL Streams
• Video Decode and Presentation API for Unix (VDPAU)
• complete solution for decoding, post-processing, compositing, and displaying
compressed or uncompressed video streams
•All open source projects

39. 39
GLVND: GL Vendor-Neutral Dispatch library
• libglvnd
• Arbitrates OpenGL API calls between multiple vendors
• Multiple drivers from different vendors to coexist on the same file system
• Determines which vendor to dispatch each API call to at runtime
• Both GLX and EGL are supported
• Any combination with OpenGL and OpenGL ES (1.1, 2.0, 3.x)
• NVIDIA open source contribution
• https://github.com/NVIDIA/libglvnd

40. 40
Before GLVND
NVIDIA Proprietary
Linux Driver
Mesa + Nouveau
I control OpenGL
best on NVIDIA
GPUs
But I got
here first!
Drivers driving you crazy!
I just want my
Linux window
system to start!
pre-GLVND user

41. 41
GLVND Architecture
libOpenGL
mapi/glapi
libGLdispatch
libGLX
libGL
X11 Server
GLX_EXT_libglnvd
extension
GLX_vendor GLX_vendor2
OpenGL or ES Application

42. 42
NVIDIA’s Support for Wayland
• Wayland
• Intended as simpler replacement for X Window System
• A protocol for a compositor to talk to its clients
• Plus the C library implementation of that protocol
• Depends on a compositor (e.g. Weston) that is the display server
• Supports varying window managers (e.g. Mutter for Gnome)
• Wayland is supported on NVIDIA GPUs through EGL Streams
• Using NVIDIA’s Proprietary OpenGL driver performance & quality
• Both Weston and Mutter (used by gnome-shell) currently have EGL Stream support
• Although not by default
• See https://github.com/NVIDIA/egl-wayland
• NVIDIA open source project

43. 43
Latest VDPAU Support
•Video Decode and Presentation API for
Unix (VDPAU)
• https://www.freedesktop.org/wiki/Software/VDPAU/
•Now for latest NVIDIA GPUs (GeForce
1080, etc.)
• Supports VDPAU Feature Set H
• Hardware-accelerated decoding of
8192x8192 (8k) H.265/HEVC video streams
• Full support of HEVC Main12 profile
VDPAU Data Flow

44. 44

45. 45
What is Vulkan?
•Modern explicit API for GPU programming
• Open standard, cross-platform, multi-vendor
• 3D Graphics + Compute for modern era of GPUs
• NOT backward compatible with OpenGL
•Motivations
• Multi-thread / multi-core friendly
• Greatly reduce CPU overhead, for both application & driver
• Same API for desktop and mobile use
• More predictable performance
•Announced February 2016
• How are we doing 18 months in?

46. 46
Vulkan Extensions Supported by NVIDIA
• NVIDIA Vulkan driver already supports 50+ extensions, primarily multi-vendor
KHR_swapchain
KHR_16bit_storage
KHR_bind_memory2
KHR_descriptor_update_template
KHR_dedicated_allocation
KHR_get_memory_requirements2
KHR_image_format_list
KHR_maintenance1
KHR_maintenance2
KHR_push_descriptor
KHR_relaxed_block_layout
KHR_sampler_mirror_clamp_to_edge
KHR_sampler_ycbcr_conversion
KHR_shader_draw_parameters
KHR_storage_buffer_storage_class
KHR_external_memory
KHR_external_memory_win32
KHR_external_semaphore
KHR_external_semaphore_win32
KHR_win32_keyed_mutex
KHR_external_fence
KHR_external_fence_win32
KHR_variable_pointers
KHX_device_group
KHX_external_memory
KHX_external_memory_win32
KHX_external_semaphore
KHX_external_semaphore_win32
KHX_external_fence
KHX_external_fence_win32
KHX_multiview
KHX_win32_keyed_mutex
KHX_subgroup
EXT_blend_operation_advanced
EXT_discard_rectangles
EXT_sampler_filter_minmax
EXT_shader_subgroup_ballot
EXT_shader_subgroup_vote
NV_clip_space_w_scaling
NV_dedicated_allocation
NV_external_memory
NV_external_memory_win32
NV_fill_rectangle
NV_fragment_coverage_to_color
NV_framebuffer_mixed_samples
NV_glsl_shader
NV_win32_keyed_mutex
NV_sample_locations
NV_sample_mask_override_coverag
e
NV_viewport_array2
NV_viewport_swizzle
NV_geometry_shader_passthrough
NVX_device_generated_commands
NVX_multiview_per_view_attributes

47. 47
NVIDIA Vulkan in 2017 Provides
Vulkan’s Maximally Available Superset
Pascal
Extensions
Maxwell
Extensions
OpenGL compatibility
NVIDIA Multi-generation
GPU Initiatives
Khronos Standard
NVIDIA Initiatives
GPU Generation Features
Khronos Vulkan
Extensions (KHR)
Broad
VkPhysicalDevice-
Features
Vulkan 1.0
Device Generated
Commands
Multi-vendor
Multi-vendor (EXT)
Efforts
advanced
blending
common
shader
features
Interop Multi-GPU
etc.

48. 48
NVIDIA’s Vulkan Exposes Extensions for
Multi-vendor, Maxwell, & Pascal Features in 2017
Multiply
Difference
Linear Dodge
High-quality 2D shape rendering
VK_NV_sample_mask_override_coverage
& VK_NV_framebuffer_mixed_samples
Advanced blend modes via
EXT_blend_operation_advanced
Two examples

49. 49
• Different from implicit multi-GPU for OpenGL and Direct3D,
multi-GPU in Vulkan is explicit
• Idea is application controls multi-GPU operation for most efficient operation
• Use VK_KHX_device_group and VK_KHX_device_group_creation
• Multiple Physical Devices is referenced by a single Logical Device
New Multi GPU Support for Vulkan
Logical
Resources/Memory
Command Queues
Pipelines
Bindings
Physical
Device Group

50. 50
Device-Generated Commands for Vulkan
• Think of a step beyond AZDO (Approaching Zero Driver Overhead)
• Not only can the GPU build variable geometry batches to feed itself
• Also GPU can even generate its own commands to feed with the geometry!
• Available today with experimental Vulkan extension NVX_device_generated_commands
Draw indirect
# primitives
# instances
Multi Draw Indirect
multiple draws
at different index/vertex
offsets
OpenGL’s NV_command_list
& Vulkan’s vkCmdDrawIndirect
Change shader inputs
for each draw call
VK_NVX_device_-
generated_commands
Change pipeline state
per draw

51. 51
GPU API Interoperability
Video Decode and
Presentation API for Unix
VDPAU

52. 52
GPU “Interop” Usage
•Increasingly applications want to share GPU resources and mix APIs
• Typically sophisticated applications
•APIs involved might be
• Graphics (OpenGL, Vulkan, Direct3D)
• Compute (OpenCL, CUDA)
• Video encode and decode (VDAPU, NVENC, NVDEC, Windows Media)
•Multiple motivations for cross-process GPU resource sharing
• Performance (don’t read back to CPU), latency control (VR compositing)
• Robustness (isolation)
• Security, including protecting digital media assets
•Interop = jargon for two things
• Sharing GPU resources among different APIs
• Sharing GPU resources across process boundaries
• For example, a display compositor

53. 53
Past Interop Extensions for OpenGL
•Past interoperability extensions would pair OpenGL concepts to those
of another one particular GPU API
• Often exposed as proprietary extensions
• Typically tied to platform concepts (e.g. Win32 HANDLEs)
• Simple when API concepts match (e.g. OpenGL textures to Direct3D Surfaces)
•Examples
• NV_DX_interop mixed OpenGL and Direct3D 9
• NV_DX_interop2 mixes OpenGL and Direct3D 10 & 11
• NV_vdpau_interop mixes OpenGL and Linux VDAPAU video input/output surfaces
• Additionally, CUDA & OpenCL have interop to OpenGL
•Worked well as designed BUT...

54. 54
Responding to New Interop Requirements
• Addressing criticism of prior interop extensions...
• In many cases, single-vendor and proprietary extensions
• Can we strive for something multi-vendor?
• Overcoming NEW Managed vs. Explicit GPU API philosophy mismatches
• Older GPU APIs (e.g. OpenGL, Direct3D 9,10,11) manage GPU resources and their
underlying memory as one
• Older APIs have textures, buffers, and synchronization objects
• New GPU APIs (e.g. Vulkan, Direct3D 12) uses lower-level mechanisms to manage
resources
• Newer explicit APIs have explicit memory allocations and semaphores
• Noticeable lack of common interop infrastructure
• Can there be some common framework for interop
• Isolate platform-specific methods to “import” objects into platform-specific extension
• Windows uses HANDLEs, etc.
• POSIX operating systems use file descriptors

55. 55
Vulkan Interop Extensions
•VK_KHR_external_memory
•Allows Vulkan to export or import handles of underlying resources
•Follows normal memory aliasing rules – with some strict exceptions
Device/Instance
Memory
Allocation
Resource
(buffer/image)
VK_KHR_external_memory
External
Resource
Device/Instance

56. 56
OpenGL Provides
GL_EXT_memory_object & GL_EXT_semaphore
• Vulkan introduces explicit memory and synchronization objects
• GL_EXT_memory_object imports Vulkan explicit memory objects to OpenGL
• GL_EXT_semaphore imports Vulkan semaphore objects to OpenGL
• Extra interop mechanisms need to share GPU objects due to this
• Platform-specific extensions specify how to import memory objects & semaphores
• For POSIX systems (e.g. Linux), use GL_EXT_memory_object_fd & GL_EXT_sempahore_fd
• fd = POSIX file descriptor
• For Windows, use GL_EXT_memory_object_win32 & GL_EXT_semaphore_win32
• Uses either Win32’s opaque HANDLE type or KMT share handle
• KMT = Kernel-Mode Thunk interface for Windows Display Driver Model (WDDM)
• Also for interoperability with Direct3D 11 & 12
• Also EXT_win32_keyed_mutex provides access to the keyed synchronization primitive of
Direct3D image objects

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OpenGL’s GL_EXT_semaphore
• Introduces new object matching Vulkan-style semaphores
• Basic operations on semaphores
• Object management
• glGenSemaphoresEXT generates semaphore object names
• glDeleteSemaphoresEXT deletes semaphore objects
• Parameter setting & querying
• glSemaphoreParameterui64vEXT & GetSemaphoreParameterui64vEXT
• Semaphore parameters are platform dependent (e.g. GL_D3D12_FENCE_VALUE_EXT)
• Semaphore operations
• glSignalSemaphoreEXT signals a semaphore
• glWaitSemaphoreEXT waits until something signals the semaphore

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OpenGL’s GL_EXT_memory_object
• Introduces new memory object corresponding to Vulkan concept
• Import memory objects with platform-specific API
• Then “carve out” managed OpenGL textures and buffers from a memory object
• Commands to make textures: glTexStorageMem1DEXT, glTexStorageMem2DEXT,
glTexStorageMem3DEXT, glTexStorageMem2DMultisampleEXT,
glTexStorageMem3DMultisampleEXT
• Also Direct State Access (DSA) versions: glTextureStorageMem2DEXT, etc.
• Commands to carve out a buffer: glBufferStorageMemEXT,
glNamedBufferStorageMemEXT

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Last Words
•OpenGL 4.6 now on NVIDIA GPUs
• Zero-day driver, available on announce day
• SPIR-V now core feature of OpenGL
• Best OpenGL yet
•NVIDIA supports open source graphics initiatives
• GLVND, Wayland EGL stream support, VDPAU
•NVIDIA’s Vulkan 1.0 has 50+ extensions
• Multi-GPU support
• Maxwell & Pascal GPU features now exposed in Vulkan
• Device-Generated Commands (DGC)
•Interoperability now available for OpenGL and Vulkan

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SIGGRAPH Paper Using Vulkan & OpenGL to Check Out
• How to make shaders modular without giving
up performance
• Open source on github
• Accompanied by OpenGL and Vulkan demo
• Wednesday, 2 August
• Los Angeles Convention Center, Room 150/151
• 10:45 am - 12:35 pm