Mantle for Developers
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Mantle is a new low-level graphics API from EA that aims to simplify advanced game development and improve performance. It provides developers with more control over the GPU for optimizations. Mantle exposes the true capabilities of modern graphics hardware in a way that is accessible to developers. This allows for innovations like improved multi-GPU support, explicit resource management, and asynchronous compute. Mantle promises benefits like reduced driver overhead, better multi-threading, and more flexibility to optimize for all GPUs. EA sees Mantle driving future Frostbite engine designs by enabling new rendering techniques and optimizations.
Mantle for Developers
- 1. MANTLE FOR DEVELOPERS JOHAN ANDERSSON – TECHNICAL DIRECTOR FROSTBITE ELECTRONIC ARTS
- 2. Mantle? Simplify advanced development Improve performance Enable developers to innovate Challenge the status quo
- 4. Developer impact areas Control CPU performance Programmability GPU performance Platforms
- 5. Control New model Traditional Model: Black Box Explicit Model: Mantle Middle-ground abstraction – compromise between performance & “usability” Thin low-level abstraction to expose how hardware works Hidden resource memory & state App explicit memory management Resource CPU access tied to device context Resources are globally accessible Driver analyzes & synchronizes implicitly App explicit resource state transitions
- 6. Control App responsibility Tell when render target will be used as a texture ‒ And many more resource state transitions Don’t destroy resources that GPU is using ‒ Keep track with fences or frames Manual dynamic resource renaming ‒ No DISCARD for driver resource renaming Resource memory tiling Powerful validation layer will help!
- 7. Control Explicit control enables App high-level decisions & optimizations ‒ Has full scene information ‒ Easier to optimize performance & memory Flexible & efficient memory management ‒ Linear frame allocators ‒ Memory pools ‒ Pinned memory Reduced development time ‒ For advanced game engines & apps ‒ Easier to get to target performance & robustness
- 8. Control Explicit control enables Transient resources ‒ Alias render targets within frame ‒ Major memory savings ‒ No need to pre-allocate everything Light-weight driver ‒ Easier to develop & maintain ‒ Reduced CPU draw call overhead
- 10. CPU perf Core concepts Descriptor sets Monolithic pipelines Command buffers
- 11. CPU perf Descriptor sets Table with resource references to bind to graphics or compute pipeline Image Memory Sampler Link Replaces traditional resource stage binding ‒ Major performance & flexibility advantage ‒ Closer to how the hardware works Example 1: Single simple dynamic descriptor set ‒ Bind everything you need for a single draw call ‒ Close to DX/GL model but share between stages Dynamic descriptor set VertexBuffer (VS) Texture0 (VS+PS) Constants (VS) Texture1 (PS) App managed - lots of strategies possible! ‒ Tiny vs huge sets ‒ Single vs multiple ‒ Static vs semi-static vs dynamic Texture2 (PS) Sampler0 (VS+PS)
- 12. CPU perf Descriptor sets Table with resource references to bind to graphics or compute pipeline Image Example 2: Reuse static set with nesting ‒ Reduce update time & memory usage Memory Static descriptor set Sampler Link Dynamic descriptor set Replaces traditional resource stage binding ‒ Major performance & flexibility advantage ‒ Closer to how the hardware works Constants (VS) Link VertexBuffer (VS) Texture0 (VS+PS) Texture1 (PS) Texture2 (PS) Texture3 (PS) App managed - lots of strategies possible! ‒ Tiny vs huge sets ‒ Single vs multiple ‒ Static vs semi-static vs dynamic Texture4 (PS) Sampler0 (VS+PS) Sampler1 (PS)
- 13. CPU perf Monolithic pipelines Shader stages & select graphics state combined into single object ‒ No runtime compilation or patching needed! ‒ Significantly less runtime overhead to use Pipeline state Supports parallel building & caching ‒ Fast loading times Usage & management up to the app ‒ Static vs dynamic creation ‒ Amount of pipelines ‒ State usage IA DB VS HS DS Tessellator GS RS PS CB
- 14. CPU perf Command buffers Issue pipelined graphics & compute commands into a command buffer ‒ Bind graphics state, descriptor sets, pipeline ‒ Draw calls ‒ Render targets ‒ Clears ‒ Memory transfers ‒ NOT: resource mapping Fully independent objects ‒ Create multiple every frame ‒ Or pre-build up front and reuse
- 15. CPU perf DX/GL parallelism CPU 0 CPU 1 CPU 2 Game Game Game Render Render Driver Render Automatically extracts parallelism out of most apps Doesn’t scale beyond 2-3 cores Additional latency Driver thread often bottleneck – can collide app threads Render
- 16. CPU perf Parallel dispatch with Mantle CPU 0 Game Game Game CPU 1 Render Render Render CPU 2 Render Render Render CPU 3 Render Render Render CPU 4 Render Render Render App can go fully wide with its rendering – minimal latency Close to linear scaling with CPU cores No driver threads – no overhead – no contention Frostbite’s approach on all consoles – and on PC with Mantle!
- 17. GPU performance
- 18. GPU perf GPU optimizations Thanks to improved CPU performance – CPU will rarely be a bottleneck for the GPU ‒ CPU could help GPU more: ‒ Less brute force rendering ‒ Improve culling Resource states ‒ Gives driver a lot more knowledge & flexibility ‒ Apps can avoid expensive/redundant transitions, such as surface decompression Expose existing GPU functionality Shader pipeline object – driver optimizations ‒ Can optimize with pipeline state knowledge ‒ Can optimize across all shader stages ‒ Quad & Rect-lists ‒ HW-specific MSAA & depth data access ‒ Programmable sample patterns ‒ And more..
- 19. GPU perf Queues Modern GPUs are heterogeneous machines with multiple engines Graphics ‒ Graphics pipeline ‒ Compute pipeline(s) ‒ DMA transfer ‒ Video encode/decode ‒ More… Mantle exposes queues for the engines + synchronization primitives Compute DMA ... Queues GPU
- 21. GPU perf Queue use cases Async DMA transfers ‒ Copy resources in parallel with graphics or compute Copy DMA Graphics Render Other render Use copy
- 22. GPU perf Queue use cases Async DMA transfers ‒ Copy resources in parallel with graphics or compute Async compute together with graphics ‒ ALU heavy compute work at the same time as memory/ROP bound work to utilize idle units Compute Graphics GBuffer Non-shadowed lighting Shadowmap 0 Shadowmap 1 Final lighting
- 23. GPU perf Queue use cases Async DMA transfers Multiple compute kernels collaborating ‒ Copy resources in parallel with graphics or compute ‒ Can be faster than über-kernel ‒ Example: Compute geometry backend & compute rasterizer Async compute together with graphics ‒ ALU heavy compute work at the same time as memory/ROP bound work to utilize idle units Compute 0 Compute 1 Graphics Compute Geometry Compute Rasterizer Ordinary Rendering
- 24. GPU perf Queue use cases Async DMA transfers Multiple compute kernels collaborating ‒ Copy resources in parallel with graphics or compute ‒ Can be faster than über-kernel ‒ Example: Compute geometry backend & compute rasterizer Async compute together with graphics ‒ ALU heavy compute work at the same time as memory/ROP bound work to utilize idle units Compute Graphics Process0 Process1 Draw0 Compute as frontend for graphics pipeline ‒ Compute runs asynchronously ahead and prepares & optimizes geometry for graphics pipeline Process0 Draw1 Draw2
- 25. GPU perf Queue use cases Async DMA transfers Multiple compute kernels collaborating ‒ Copy resources in parallel with graphics or compute ‒ Can be faster than über-kernel ‒ Example: Compute geometry backend & compute rasterizer Async compute together with graphics ‒ ALU heavy compute work at the same time as memory/ROP bound work to utilize idle units Compute as frontend for graphics pipeline ‒ Compute runs asynchronously ahead and prepares & optimizes geometry for graphics pipeline Game engines will build large GPU job graphs ‒ Move away from single sequential submission ‒ Just as we already have done on CPU
- 26. Programmability
- 27. Programmability Explicit Multi-GPU Explicit control of GPU queues and synchronization, finally! ‒ Implement your own Alternate-Frame-Rendering ‒ Or something more exotic.. Use case: Workstation rendering with 4-8 GPUs ‒ Super high-quality rendering & simulation ‒ Load balance graphics & compute job graphs across GPUs ‒ 20-40 TFlops in a single machine! Use case: Low-latency rendering ‒ Important for VR and competitive games ‒ Latency optimized GPU job graph scheduling ‒ VR: Simultaneously drive 2 GPUs (1 per eye)
- 28. Programmability New mechanisms Command buffer predication & flow control ‒ GPU affecting/skipping submitted commands ‒ Go beyond DrawIndirect / DispatchIndirect ‒ Advanced variable workloads ‒ Advanced culling optimizations Write occlusion query results into GPU buffer ‒ No CPU roundtrip needed ‒ Can drive predicated rendering ‒ Or use results directly in shaders (lens flares)
- 29. Programmability Bindless resources Mantle supports bindless resources ‒ Shaders can select resources to use instead of static binding from CPU ‒ Extension of the descriptor set support Examples ‒ Performance optimizations – less data to update ‒ Logic & data structures that live fully on the GPU ‒ Scene culling & rendering ‒ Material representations Key component that will open up a lot of opportunities! ‒ Deferred shading ‒ Raytracing
- 30. Platforms
- 31. Platforms Today Mantle gives us strong benefits on Windows today ‒ Console-like performance & programmability on both Windows 7 and Windows 8 ‒ For us, well worth the dev time! DX & GL are the industry standards ‒ Needed for platforms that do not support Mantle ‒ Needed by devs who do not want/need more control ‒ Have to have fallback paths for GL/DX, but not limit oneself to it Mantle and PlayStation 4 will drive our future Frostbite designs & optimizations ‒ PS4 graphics API has great programmability & performance as well ‒ Share concepts, methods & optimization strategies
- 32. Platforms Linux & Mac Want to see Mantle on Linux and Mac! ‒ Would enable support for our full engine & rendering ‒ Significantly easier to do efficient renderer with Mantle than with OpenGL Use cases: ‒ Workstations ‒ R&D ‒ Not limited by WDDM ‒ Games ‒ Mantle + SteamOS = powerful combination!
- 33. Platforms Mobile Mobile architectures are getting closer in capabilities to desktop GPUs Want graphics API that allows apps to fully utilize the hardware ‒ Power efficient ‒ High performance ‒ Programmable Major opportunity with Mantle – leap frog GL4, DX11 ‒ For mobile SoC vendors ‒ For Google and Apple
- 34. Platforms Multi-vendor? Mantle is designed to be a thin hardware abstraction ‒ Not tied to AMD’s GCN architecture ‒ Forward compatible ‒ Extensions for architecture- and platform-specific functionality Mantle would be a much more efficient graphics API for other vendors as well ‒ Most Mantle functionality can be supported on today’s modern GPUs Want to see future version of Mantle supported on all platforms and on all modern GPUs! ‒ Become an active industry standard with IHVs and ISVs collaborating ‒ Enable us developers to innovate with great performance & programmability everywhere
- 36. Frostbite Battlefield 4 Mantle support is in development ‒ Core renderer (closer to PS4 than DX11) ‒ Implement all rendering techniques used in BF4 (many!) ‒ CPU optimizations (parallel dispatch, descriptor sets) ‒ GPU optimizations (minimize transitions, MSAA) ‒ R&D for advanced GPU optimizations ‒ Memory management ‒ Multi-GPU support ‒ ~2 months of work Update targeting late December
- 37. Frostbite Plants vs Zombies: Garden Warfare Very different rendering compared to BF4 Frostbite Mantle renderer will work out of the box Focus on APU performance
- 38. Frostbite Future All Frostbite games designed with Mantle ‒ 15 games in development across all of EA Advanced Mantle rendering & use cases ‒ Lots of exciting R&D opportunities! Want multi-vendor & multi-platform support!
Editor's Notes
- #3: So what is Mantle?Mantle is a low-level graphics API and it’s goals are to improve performance and make easier to develop these really advanced application and give developers a lot of freedom to build innovative graphics solutions.And it is a bit of a challenge to the established order of things, which I think is fun and healthy for the industry
- #4: We’ve been working with Mantle for some time now and adding support in our engine Frostbite and Battlefield 4. And I wanted to share some of our learnings and what Mantle can mean in general for developers
- #12: Can be of any sizeSingle per-draw call small dynamic descriptor setStatic + dynamicMultiple ones nested by update frequency
- #13: Can be of any sizeSingle per-draw call small dynamic descriptor setStatic + dynamicMultiple ones nested by update frequency
- #15: Not needed for:Resource mapping´No implicit pipeline flushingMuch easier to track down stalls in the app itself
- #28: Also foveated rendering
- #30: ? Need to go beyond HLSL for pointer support in shaders
- #34: What is next after OpenGL ES3?
- #38: Kaveri