Vulkan: Scaling to Multiple Threads. Kevin sun Lead Developer Support Engineer, APAC PowerVR Graphics

Transcription

1 Vulkan: Scaling to Multiple Threads Kevin sun Lead Developer Support Engineer, APAC PowerVR Graphics

2 Introduction Who am I? Kevin Sun Working at Imagination Technologies Take responsibility for PowerVR technical support in APAC region Imagination Technologies Vulkan: High efficiency on mobile

3 Introduction This series Detailed look at Vulkan No new information about the API Khronos job! Adding context to existing information Primarily from SIGGRAPH This week: Scaling to multiple threads Imagination Technologies Vulkan: High efficiency on mobile

4 GPU waiting on the CPU?

5 GPU waiting on the CPU Graphics Apps can be bottlenecked by CPU Down to driver overhead of the API Maximum draw calls Particular problem on mobile Less CPU power than desktop Hang on, I ve done this slide before Imagination Technologies Vulkan: High efficiency on mobile

6 GPU waiting on the CPU (again) Multi-core CPUs Modern CPUs have many cores Apps use many threads OpenGL ES is limited to a single core At least broadly speaking There are options, but they don t scale well Nexus player has 4 hw threads OpenGL ES Gnome Horde can only use 1! Imagination Technologies Vulkan: High efficiency on mobile

7 Making use of all the cores

8 Making use of all the cores Using all cores can give better performance And efficiency! Not just important to use cores Must scale effectively Less useful if more work overall Gnome Horde shows the effects of this Imagination Technologies Vulkan: High efficiency on mobile

9 Vulkan mechanisms for scaling

10 Vulkan mechanisms for scaling Not threading for you in the background Explicit API! Gives application tools Use them wisely! Multi-threading friendly design Optimised to not block Imagination Technologies Vulkan: High efficiency on mobile

11 Vulkan mechanisms for scaling No Global State OpenGL ES Global State Current Context TLS! Lookups into bound state Vulkan No global state Everything contained in objects Direct state access Imagination Technologies Vulkan: High efficiency on mobile

12 Vulkan mechanisms for scaling External Synchronization OpenGL ES All functions are safe to call from multiple threads Driver uses mutexes or other locks No knowledge of application s usage Vulkan Only concurrent reading is safe Driver does not lock on modifications Application manages threads Imagination Technologies Vulkan: High efficiency on mobile

13 Vulkan mechanisms for scaling Multi-threaded command generation OpenGL ES No separation of command generation and submission Draw call translates state to hardware, and submits it Expensive, and typically on a single thread Vulkan Commands recorded into command buffers Submit command buffers to a queue, separately Imagination Technologies Vulkan: High efficiency on mobile

14 Vulkan mechanisms for scaling Multi-threaded command generation Imagination Technologies Vulkan: High efficiency on mobile

15 Vulkan mechanisms for scaling Multi-threaded command generation Command buffers require memory Dynamically allocated - expensive! Command Buffers can be reset Re-use the memory and re-record Command Pools group command buffers Allows multiple command buffers to share More stability of per-pool memory than per-buffer Imagination Technologies Vulkan: High efficiency on mobile

16 Conclusion

17 Conclusion Flexibility to scale Completely app controlled Lots of design work to enable this Multi-threaded Command Generation No global state or implicit synchronization Better use of modern CPUs No more maxing out one core Not possible before Imagination Technologies Vulkan: High efficiency on mobile

18 Vulkan: Scaling to Multiple Threads Kevin sun Lead Developer Support Engineer, APAC PowerVR Graphics