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Unity Profiler Crash Course

· Performance & Optimization ·
#Unity#Optimization#Profiler#CPU#GPU#Memory#Rendering

This note covers the basics of Unity’s built-in Profiler: opening the window, understanding the key modules (CPU, GPU, Memory, Rendering), and reading the Timeline / Hierarchy panes to find bottlenecks.

Run it whenever the project needs a health check or frame time spikes.

1. Opening the Profiler

Menu path: Window → Analysis → Profiler

Profiler menu

Inside the window you can:

  • Profile the Editor directly; or
  • Connect to a device / standalone Player via the dropdown at the top

Once connected the curves start streaming per-frame data.

2. Common modules overview

Use the Modules dropdown to pick what you care about:

  • CPU Usage – scripts, rendering, physics, GC, UI, etc.
  • GPU Usage – GPU pipeline stages
  • Memory – textures, meshes, audio, GC heap usage
  • Rendering – batches, SetPass, draw calls, visible objects

Toggle modules on/off to reduce noise while focusing on one area.

3. CPU module: find the worst offenders

CPU Usage

Colored curves break down rendering, scripts, physics, GC, etc.

Workflow:

  1. Click on a spike frame to lock it
  2. Inspect the Timeline or Hierarchy below
  3. Track down the top few functions or systems by cost

If you see GC Alloc constantly non-zero, you are allocating managed memory each frame—look for new, captured lambdas, string concatenations, etc.

4. GPU, Memory, Rendering highlights

GPU Usage

  • Shows how long each stage (Shadows, Opaque, Transparent…) takes
  • Tells you if the GPU is the limiting factor
  • Combine with Rendering to decide whether the culprit is overdraw, shader complexity, or lighting

Memory

  • Trend of total memory, GC heap, textures, meshes, audio
  • Reveals resources that keep growing or scenes that never unload
  • Use Memory Profiler for deeper investigation

Rendering

  • Batches / SetPass / Draw Calls
  • Visible objects, dynamic batching, SRP Batcher status
  • Large spikes hint at missing culling, too many materials, or heavy UI

5. Timeline vs. Hierarchy

Both panes are at the bottom of the Profiler window.

Timeline

  • Displays each system/function as horizontal bars per frame
  • Bar length == time spent, nested bars show call stacks
  • Hover to see detailed info

Technique: pick a high CPU spike, switch to Timeline, and expand the longest colored block (e.g., Scripts) until you find the exact method.

Hierarchy

  • Tree list sorted by Total or Self time
  • Easy to sort and identify the slowest functions
  • Expanding nodes reveals the call hierarchy

Typically Timeline finds “which area is hot”, Hierarchy tells you “exactly which function”.

6. Practical advice

  • Record a representative gameplay segment; don’t rely on empty scenes.
  • Focus on persistent high cost rather than rare spikes (unless the spikes matter).
  • After identifying a hotspot, experiment inside that system (scripts, rendering, memory).
  • Re-run the exact same Profiler scenario after optimizations to confirm improvement.

Mastering the Profiler saves countless hours of guesswork later in production.

Original article (Chinese) on CSDN “uniGame”, CC BY-SA 4.0.
https://blog.csdn.net/alla_Candy/article/details/133344430