Performance profiling in Unity - Step-by-Step Execution

Concept Flow - Performance profiling

Start Profiling

↓

Run Game Code

↓

Collect Performance Data

↓

Analyze Data

↓

Identify Bottlenecks

↓

Optimize Code

↓

Repeat Profiling

↓

End Profiling

Start profiling, run the game, collect data, analyze to find slow parts, optimize, and repeat until performance improves.

Execution Sample

Unity

Profiler.BeginSample("MyFunction");
// Code to profile
Profiler.EndSample();

This code marks the start and end of a profiling sample to measure performance of 'MyFunction'.

Execution Table

Step	Action	Profiler State	Data Collected	Result
1	Profiler.BeginSample("MyFunction") called	Profiling started for MyFunction	No data yet	Ready to measure
2	Game code inside MyFunction runs	Profiling active	Execution time accumulating	Tracking performance
3	Profiler.EndSample() called	Profiling stopped for MyFunction	Total time recorded	Sample complete
4	Analyze collected data	Profiler idle	Execution time and call count available	Identify slow parts
5	Optimize code based on data	Profiler idle	No new data yet	Code improved
6	Repeat profiling to verify	Profiling restarted	New data collected	Check improvements
7	Profiling ends	Profiler stopped	Final performance data	Performance optimized

💡 Profiling ends after collecting and analyzing performance data to optimize code.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 6	Final
Profiler State	Idle	Active (MyFunction)	Idle	Active (MyFunction)	Stopped
Execution Time	0 ms	Accumulating	Recorded (e.g. 15 ms)	Accumulating	Final (e.g. 12 ms)
Call Count	0	Incrementing	Recorded (e.g. 1)	Incrementing	Final (e.g. 1)

Key Moments - 3 Insights

Why do we need to call Profiler.BeginSample and Profiler.EndSample around the code?

These calls mark the start and end of the code section to measure. Without them, the profiler won't know which part to track, as shown in steps 1 and 3 of the execution_table.

What does the profiler measure during the active state?

During the active state (step 2), the profiler collects execution time and call count data for the marked code, which helps identify slow parts as seen in step 4.

Why do we repeat profiling after optimizing code?

Repeating profiling (step 6) verifies if the optimizations improved performance by comparing new data with previous results, ensuring changes had the desired effect.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what does the profiler do?

A Starts measuring performance

B Analyzes the data collected

C Stops measuring performance and records data

D Optimizes the code automatically

💡 Hint

Check the 'Profiler State' and 'Result' columns at step 3 in the execution_table.

According to variable_tracker, what is the 'Profiler State' after step 6?

A Active (MyFunction)

B Idle

C Stopped

D Not started

💡 Hint

Look at the 'Profiler State' row under 'After Step 6' in variable_tracker.

If we forget to call Profiler.EndSample(), what will happen according to the flow?

A Profiler will never start

B Profiler will keep measuring indefinitely

C Profiler will stop automatically after some time

D Profiler will throw an error immediately

💡 Hint

Refer to the concept_flow where profiling starts and ends explicitly with BeginSample and EndSample.

Concept Snapshot

Performance Profiling in Unity:
- Use Profiler.BeginSample("Name") before code to measure
- Run the code section
- Use Profiler.EndSample() after code to stop measuring
- Analyze collected data to find slow parts
- Optimize code and repeat profiling
- Helps improve game performance step-by-step

Full Transcript

Performance profiling in Unity involves marking sections of code with Profiler.BeginSample and Profiler.EndSample to measure how long they take to run. The profiler collects data like execution time and call count while the code runs. After stopping the sample, you analyze the data to find slow parts or bottlenecks. Then you optimize the code and profile again to check if performance improved. This cycle repeats until the game runs smoothly. The execution table shows each step from starting profiling, running code, stopping profiling, analyzing data, optimizing, and repeating. The variable tracker shows how profiler state and data change during these steps. Key moments clarify why marking code sections is necessary and why repeating profiling is important. The quiz tests understanding of profiler states and the importance of proper start and stop calls.

Practice

1. What is the main purpose of using performance profiling in Unity?

easy

A. To write story scripts for the game

B. To add new game features quickly

C. To find slow or heavy parts in your game code

D. To create game art and animations

Solution

1. Step 1: Understand performance profiling

   Performance profiling is used to check which parts of the game code take the most time or resources.

2. Step 2: Match purpose with options

   Only To find slow or heavy parts in your game code talks about finding slow or heavy parts, which matches the purpose of profiling.

3. Final Answer:

   To find slow or heavy parts in your game code -> Option C

4. Quick Check:

   Profiling purpose = find slow code [OK]

Hint: Profiling finds slow code parts to improve performance [OK]

Common Mistakes:

• Confusing profiling with adding features
• Thinking profiling creates art or story
• Mixing profiling with gameplay design

2. Which of the following is the correct way to mark a code section for profiling in Unity?

easy

A. Profiler.BeginSample("MyCode") and Profiler.EndSample()

B. Profiler.MarkStart("MyCode") and Profiler.MarkEnd()

C. Profiler.StartSample("MyCode") and Profiler.StopSample()

D. Profiler.Profile("MyCode")

Solution

1. Step 1: Recall Unity profiling API

   Unity uses Profiler.BeginSample and Profiler.EndSample to mark code sections.

2. Step 2: Compare options with correct API

   Only Profiler.BeginSample("MyCode") and Profiler.EndSample() matches the exact method names used in Unity.

3. Final Answer:

   Profiler.BeginSample("MyCode") and Profiler.EndSample() -> Option A

4. Quick Check:

   Correct API = BeginSample and EndSample [OK]

Hint: Use BeginSample and EndSample to mark profiling code [OK]

Common Mistakes:

• Using StartSample/StopSample instead of BeginSample/EndSample
• Using non-existent Profiler methods
• Forgetting to call EndSample after BeginSample

3. What will be the output in the Unity Profiler if you run this code snippet?

Profiler.BeginSample("HeavyTask");
for (int i = 0; i < 1000000; i++) { var x = Mathf.Sqrt(i); }
Profiler.EndSample();

medium

A. The Profiler shows a sample named 'HeavyTask' with time taken for the loop

B. The Profiler shows an error because of missing Profiler.StopSample()

C. No profiling data is recorded because Profiler.BeginSample is inside a loop

D. The Profiler shows a sample named 'HeavyTask' but with zero time

Solution

1. Step 1: Understand Profiler.BeginSample and EndSample usage

   The code marks the start and end of a heavy task loop, so the Profiler records the time spent inside.

2. Step 2: Analyze Profiler output

   The Profiler will show a sample named 'HeavyTask' with the time taken to run the loop, which is significant.

3. Final Answer:

   The Profiler shows a sample named 'HeavyTask' with time taken for the loop -> Option A

4. Quick Check:

   Profiler records marked code time = The Profiler shows a sample named 'HeavyTask' with time taken for the loop [OK]

Hint: Profiler shows time for code between BeginSample and EndSample [OK]

Common Mistakes:

• Confusing EndSample with StopSample
• Thinking profiler needs to be inside the loop
• Assuming profiler shows zero time for heavy code

4. Identify the error in this profiling code snippet:

Profiler.BeginSample("UpdateLoop");
UpdateGameObjects();
// Missing Profiler.EndSample()

medium

A. Profiler.BeginSample() should be called after UpdateGameObjects()

B. No error, the code is correct

C. Profiler.BeginSample() and EndSample() cannot be used in Update()

D. Profiler.EndSample() is missing, causing incorrect profiling data

Solution

1. Step 1: Check profiling code structure

   Profiler.BeginSample must be paired with Profiler.EndSample to mark the code section properly.

2. Step 2: Identify missing EndSample call

   The code is missing Profiler.EndSample(), which causes the Profiler to not close the sample and gives wrong data.

3. Final Answer:

   Profiler.EndSample() is missing, causing incorrect profiling data -> Option D

4. Quick Check:

   Missing EndSample causes profiling errors [OK]

Hint: Always pair BeginSample with EndSample to avoid errors [OK]

Common Mistakes:

• Forgetting to call EndSample after BeginSample
• Calling BeginSample after the code instead of before
• Thinking profiling can't be used in Update()

5. You want to profile two different parts of your game code separately: physics calculations and AI updates. How should you use the Profiler API to get clear timing for both?

hard

A. Call Profiler.BeginSample("Physics") once at game start and Profiler.EndSample() at game end, same for AI

B. Call Profiler.BeginSample("Physics") before physics code and Profiler.EndSample(), then Profiler.BeginSample("AI") before AI code and Profiler.EndSample()

C. Use Profiler.BeginSample("Physics") and Profiler.BeginSample("AI") at the same time without EndSample()

D. Only use Profiler.EndSample() after both physics and AI code without BeginSample()

Solution

1. Step 1: Understand separate profiling sections

   To profile two parts separately, you must mark each section with its own BeginSample and EndSample calls.

2. Step 2: Apply correct usage for both parts

   Call Profiler.BeginSample("Physics") before physics code and Profiler.EndSample(), then Profiler.BeginSample("AI") before AI code and Profiler.EndSample() correctly calls BeginSample and EndSample around physics code, then again around AI code, giving clear timing for each.

3. Final Answer:

   Call Profiler.BeginSample("Physics") before physics code and Profiler.EndSample(), then Profiler.BeginSample("AI") before AI code and Profiler.EndSample() -> Option B

4. Quick Check:

   Separate samples need separate BeginSample/EndSample pairs [OK]

Hint: Use separate BeginSample/EndSample pairs for each code section [OK]

Common Mistakes:

• Calling BeginSample once for whole game session
• Starting two samples without ending them
• Using EndSample without matching BeginSample