LPGPU Workshop on Power-Efficient GPU and Many-core Computing (PEGPUM 2014)

Transcription

1 A practitioner s view of challenges faced with power and performance on mobile GPU Prashant Sharma Samsung R&D Institute UK LPGPU Workshop on Power-Efficient GPU and Many-core Computing (PEGPUM 2014) SERI 1

2 Outline Mobile GPU challenges Using GPUs efficiently Results SRUK 2

3 Challenges Issue Desktop devices are too big for portable use Solutions Smaller screens Smaller GPU chips, buses, heat sinks SRUK 3

4 Challenges Issue With desktop pixel density, not enough pixels to display effectively Solutions Increase the screen resolution SRUK 4

5 Challenges Issue Increase resolution & small size leaves no space for required memory bus Solutions Shared GPU & CPU memory Use system memory for framebuffer SRUK 5

6 Shared Memory DDR3 RAM Desktop CPU(s) Mobile CPU(s) Cache Mobile GPU(s) Cache PCIe Desktop GPU(s) Shared bus DDR3 RAM GDDR5 RAM CPU and GPU to share their memory bus mobile devices are bandwidth-constrained SRUK 6

7 Challenges Issue Shrinking desktop GPU won t handle high resolutions desktop needs big fans and heat sinks Solutions Increase rendering & framebuffer bandwidth efficiency Tiling instead of immediate rendering Compression Wiki SRUK 7

8 Immediate mode Each triangle is processed once, in order Bad locality of reference Can cause overdraw SRUK 8

9 Immediate mode SRUK 8

10 Immediate mode SRUK 8

11 Immediate mode SRUK 8

12 Immediate mode SRUK 8

13 Immediate mode SRUK 8

14 Immediate mode SRUK 8

15 Immediate mode SRUK 8

16 Immediate mode SRUK 8

17 Immediate mode SRUK 8

18 Immediate mode SRUK 8

19 Immediate mode SRUK 8

20 Immediate mode SRUK 8

21 Immediate mode SRUK 8

22 Immediate mode SRUK 8

23 Tile mode Process tiles one at a time Draw all the triangles in a tile SRUK 9

24 Tile mode SRUK 9

25 Tile mode SRUK 9

26 Tile mode SRUK 9

27 Tile mode SRUK 9

28 Tile mode SRUK 9

29 Tile mode SRUK 9

30 Tile mode SRUK 9

31 Tile mode SRUK 9

32 Tile mode SRUK 9

33 Tile mode SRUK 9

34 Tile mode SRUK 9

35 Tile mode SRUK 9

36 Tile mode SRUK 9

37 Compressed Texture ASTC 8, 3.56 and 2 bits/pixel Wikipedia Smaller texture footprints Reduce the size of transfer Compress texture SRUK 10

38 Challenges Issue Tiled rendering traverses the geometry repeatedly Work in Progress Tessellation Subdivision surfaces SRUK 11

39 SERI Using GPUs efficiently

40 Profiling Performance CPU Usage Threads, functions, core frequencies GPU Usage Vertex, Fragment work load GPU frequencies Frame rate SRUK 12

41 Profiling Performance Tools Offline compilers OpenGL ES tracer Systrace, TraceView DS-5, PVRTune, PerfHUD ES Adreno SRUK 13

42 Profiling Power Current Power Voltage Tools ARM Energy probe, NI DAQ unit Power model (GPU, CPU load -> Power) SRUK 14

43 Profiling- Load Analysis CPU Vertex Shader Fragment Shader Bandwidth Memory SRUK 15

44 CPU Bound Reasons Are you doing too many draw calls? A lot of calculations (physics, animation) Solutions Combine draw calls Reduce state changes by reordering draw calls Simplify calculations Use multithreading or SIMD SRUK 16

45 Vertex Bound Reasons Complex geometry Too much computation per vertex Solutions Use level of detail (LoD) Use culling Remove unnecessary vertices Silhouette SRUK 17

46 Fragment Bound Reasons Overdraw Too much computation per fragment Solutions Reduce the use of transparency Draw object front to back Deferred shading SRUK 18

47 Bandwidth Bound Reasons Using a lot of textures Poor locality of reference Solutions Reduce Textures Use compressed textures ETC2, ETC, ASTC, PVRTC2, DXT Use MIP maps SRUK 19

48 API s OpenGL ES 3.0 Geometry instancing Multiple render targets ETC2 texture compression format Qualcomm Cuda, OpenCL, RenderScript Non graphics computing SRUK 20

49 Results SERI 21

50 Energy Required/Battery Disparity between mobile 3D graphics energy and battery capacity Bren Mochocki, Kanishka Lahiri, and Srihari Cadambi Power analysis of mobile 3D graphics. In Proceedings of the conference on Design, automation and test in Europe: Proceedings (DATE '06). European Design and Automation Association, 3001 Leuven, Belgium, Belgium, SRUK 22

51 Display/CPU/GPU Power 2500 Power(mW) Display CPU 500 GPU 0 Game 1 (High GPU Utilization) Game 2 (Low GPU Utilization) 3D Rendering (High GPU Utilization) 3D Rendering (Low GPU Utilization) Accurate GPU Power Estimation for Mobile Device Power Profiling, 2013 IEEE international conference, Minyong Kim,Sung Woo Chung,Korea University, SRUK 23

52 Image Processing Time (ms) Negative filter CPU GLES 2.0 OpenCL 0 240x x x x x1365 Image size For large image sizes the gain is significant SRUK 24

53 mjoules Image Processing Energy (mj) GPU 5 times better 240x x x x x1365 Image size CPU GLES OpenCL Total CPU & GPU power/display off SRUK 25

54 Compressed Texture % app1 Energy (mj ) app2 18 % UnCompressed Compressed Total Energy SRUK 26

55 Current (A) Changing FPS from application fps app1 app2 app3 Lowering the frame rate would reduce the power usage Possible solution for simple UI applications SRUK 27

56 Summary Mobile GPU not like Desktop GPU How to optimise Performance vs power Quality vs performance Reduce workload Help it & GPU is your friend... SRUK 28

57 Thank you Questions? SRUK 29