GPU-resource multiplexing in component-based systems Sebastian Sumpf < sebastian.sumpf@genode-labs.com > Josef Söntgen < josef.soentgen@genode-labs.com >
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 2
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 3
Motivation GPU-resource multiplexing in component-based systems 4
Motivation Architecture layout of an Intel Core i7 6700K processor 1 1https://software.intel.com/sites/default/files/managed/c5/9a/The-Compute-Architecture-of-Intel-Processor- Graphics-Gen9-v1d0.pdf GPU-resource multiplexing in component-based systems 5
Motivation GPUs have become freely programmable, think shader language, CUDA/OpenCL 2 2https://www.shadertoy.com/view/ldlcRf GPU-resource multiplexing in component-based systems 6
GPU machine code 3 3https://twitter.com/adamjmiles/status/821914849038966784 GPU-resource multiplexing in component-based systems 7
Maybe operating systems → should handle GPUs in a way like they do it for CPUs GPU-resource multiplexing in component-based systems 8
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 9
State of the art GPU-resource multiplexing in component-based systems 10
Complexity analysis (Intel only) Mesa library Mesa KLOC EGL 7.5 OpenGL 170 GLSL 90 i965 DRI driver 81 i915 driver ~100 KLOC GPU-resource multiplexing in component-based systems 11
Port Mesa with software rendering back end GPU-resource multiplexing in component-based systems 12
Or this GPU-resource multiplexing in component-based systems 13
Until GPU-resource multiplexing in component-based systems 14
3D software stack on Linux GPU-resource multiplexing in component-based systems 15
3D software stack on Linux 1. Observation while investigating the i915 GPU driver from Linux ◮ A lot of code to support previous IGD generations ◮ Support for many outdated features 2. Idea → Support current hardware generations (i. e., Broadwell and newer) only → Take advantage of modern features → Try to write a minimal GPU multiplexer from scratch GPU-resource multiplexing in component-based systems 16
GPU resource multiplexing on Linux GPU-resource multiplexing in component-based systems 17
Engines 1. Render engine (3D/GPGPU) 2. VCS engine (Video Command Streamer - video decode support) 3. VECS engine (Video Enhancement Command Streamer) 4. Blitter engine → Concentrate on render engine GPU-resource multiplexing in component-based systems 18
Resource management by the GPU driver 4 4 https://image.slidesharecdn.com/19gscale1-160901124550/95/xpds16-live-scalability-for-vgpu-using-gscale- xiao-zheng-intel-5-638.jpg?cb=1472733989 GPU-resource multiplexing in component-based systems 19
GGTT and PPGTT Global Graphics Translation Table (GGTT) ◮ Only one per GPU ◮ One level (8MB) ◮ 8 Byte page table entries (PTEs) point to 4KB physical pages ◮ The leading PTEs directly map into the aperture Per-process GTT (PPGTT) ◮ Hierarchical page table in various formats ◮ Gen8+ supports four level page table format ◮ 48 bit virtual-address space GPU-resource multiplexing in component-based systems 20
Aperture and fence registers Aperture ◮ Only way for way CPU to access graphics memory directly ◮ Mapped through the GTT ◮ Up to 512MB on Broadwell/Skylake Fence registers ◮ Allow to set tiling mode (X or Y) for memory area mapped through the aperture (automatic tiling/detiling on write/read access by the CPU) ◮ 32 registers on Broadwell/Skylake GPU-resource multiplexing in component-based systems 21
Ring management Physical and logical rings GPU-resource multiplexing in component-based systems 22
Command execution 1. Classical ring execution by setting the head 2. Execlists ◮ Hardware status page ◮ Register state context ◮ PPGTT context ◮ Logical-ring context ◮ HW/engine context GPU-resource multiplexing in component-based systems 23
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 24
GPU resource multiplexing in user space GPU-resource multiplexing in component-based systems 25
GPU resource multiplexing in user space GPU-resource multiplexing in component-based systems 26
And of course GPU-resource multiplexing in component-based systems 27
Something new GPU-resource multiplexing in component-based systems 28
Component based scenario GPU-resource multiplexing in component-based systems 29
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 30
Results Trusted computing base Component KLOC Microkernel 10 Genode base system < 30 Nitpicker GUI server 5 GPU multiplexer 10 GPU-resource multiplexing in component-based systems 31
State Current state Support for Mesa-based GPU clients Future Take advantage of the blitter engine Skylake, Kaby Lake, ... Future (tempting) work Virtual GPU in VirtualBox as GPU client GPU-resource multiplexing in component-based systems 32
Outline 1. Motivation 2. State of the art 3. GPU resource multiplexing in user space 4. Results 5. References GPU-resource multiplexing in component-based systems 33
References Intel’s open source community : https://01.org Ben Widawsky : https://bwidawsk.net/blog/index.php/ 2015/09/gen-graphics-and-the-urb Daniel Vetter : http://blog.ffwll.ch/2012/10/i915gem-crashcourse.html GPU-resource multiplexing in component-based systems 34
Demo GPU-resource multiplexing in component-based systems 35
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