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Table of Contents

Profiling

Resources

Profiling

An efficient profiling workflow for Unreal Engine project. PerformanceOptimization

DataFlow

- CPU and GPU are not working in parallel
- Not all rendering-related issues are related to the GPU
- Before the GPU actually renders, CPU also needs to deal with rendering tasks
- Some GPU tasks will need to wait for CPU tasks finish
- Some CPU tasks will need to wait for GPU tasks finish
- That's the reason we will see some waiting tasks in profiled result
  • Game (Game Thread): Gameplay logic + decides what should be rendered > related to CPU bottleneck, game logic too heavy
  • Darw (Render Thread): Prepares rendering work(draw calls, material permutations, culling, sorting, batching, pass...), high-level rendering abstraction > related to CPU bottleneck, scene complexity
  • RHIT (RHI Thread): translates render commands into actual GPU commands (DirectX, Vulkan, Metal...), manages GPU resources > related to CPU/GPU bottleneck (two side)
  • GPU: Actual GPU render > related to GPU bottleneck, rendering/shader overload
  • GPU is rendering frame N
  • RHI Thread is submitting frame N+1
  • Render Thread is building frame N+2
  • Game Thread is simulating frame N+3

DataFlow1 DataFlow2

HighLevelPerformanceScreenshot

  • Set up target fps first: 30 fps = 33.33 ms/frame, 60 fps = 16.66 ms/frame
  • Initial Bottleneck Identification: Is it CPU, GPU or Memory?
  • Always tackling the biggest problem first, leading to maximum performance return for the time invested
  • Finding spikes in profiled result

Common Profiling Tools

  • stat fps : Show current fps
  • stat unit : Overall frame time as well as the game thread, rendering thread, and GPU times
  • stat unitgraph : See the graph with the stat unit data
  • stat rhi : Displays Render Hardware Interface(RHI) memory and performance statistics
  • stat memory : Shows statistics on how much memory is being used by various subsystems

unit memory

ProfilingCPU

Simple Profiling Tools

  • stat game : Gives feedback on how long the various Gameplay Ticks are taking
  • stat physics : Displays physics performance statistics
  • stat anim : Shows how long skinned meshes are taking to compute per tick
  • stat navigation : Shows performance and memory information for the navigation system

Unreal Insights

  • Filter CPU tracks only CPUTask
  • Find the key funciton (or a set of functions) that cause performance issue. Search from high level to low level Tasks
  • Diagnose funciton counts and time spent NamedEvent
  • Enable Stat Named Events will be slightly heavier but provide more tracing details NamedEvent
  • Read function in source code if needed SOURCE

ProfilingGPU

Simple Profiling Tools

  • stat gpu : Displays GPU statistics for the frame
GPU
  • ProfileGPU (GPU Visualizer)
GPUVisualizer
  • Optimization view mode viewMode

Unreal Insights

  • For tracking all frames in general and finding performance spikes
  • Not for diagnose deeply into a single frame(use Render Doc instead)
  • Filter GPU tracks only FilterGPU
  • Find the key elements (or a set of elements) that cause performance issue GPUTasks
  • GPU bottleneck will block other thread's tasks GPU_Bottleneck

RenderDoc

  • For detail diagnoise of a single frame (dive deep into Draw call, Overdraw, Shader Complexity, Render target...)
  • Not for finding performance spikes (use Unreal Insights instead)
  • Texture Viewer: Viewing all textures and render targets used during the capture TextureViewer
  • Pipeline State: A complete snapshot of the GPU pipeline configuration for the currently selected draw call PipelineState
  • Mesh Viewer: A tool for inspecting the geometry produced by a draw call MeshViewer
  • Event Browser: A timeline/tree of all GPU commands recorded in the captured frame EventBrowser
  • We can search for the specific render pass in Event Browser to dive deep into it. Ex: BasePass
  • We can search for actor's display name in Event Browser to dive deep into it

Windows PIX (WIP)

ProfilingMemory

Simple Profiling Tools

  • stat memory : Shows statistics on how much memory is being used by various subsystems in Unreal Engine statMemory
  • stat streaming : Displays basic statistics on streaming assets, like how much memory streaming textures are using, or how many streaming textures there are in the scene statStreaming

Memory Insights

  • Change the path inside "RunMemoryInsight.bat" file to match with your Unreal Engine location
  • Execute "RunMemoryInsight.bat" file. This will run both Unreal Engine and Unreal Insight with memory profiling enabled Memory

Resources