DOTNET: Memory Optimization in .NET with Object Pooling

Here’s a single, self-contained console app you can run to see and feel the difference between:

• 🚫 Without Object Pooling (allocate new arrays every time)
• ✅ With Object Pooling (reuse arrays via ArrayPool<byte>)

It includes:

• Full Program.cs code
• Optional .csproj (if you want a drop-in project)
• Step-by-step how to run
• How to interpret the results

Works on any modern .NET (7/8/9/10+).

1️⃣ Full Code – Program.cs

2️⃣ Optional – Minimal .csproj (if you want full project file)

Create a file named ObjectPoolingDemo.csproj:

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <OutputType>Exe</OutputType>
    <TargetFramework>net8.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

</Project>
Code language: HTML, XML (xml)

You can also change net8.0 to net9.0 or later (e.g., net10.0) depending on your installed SDK.

3️⃣ Step-by-Step: How to Run This Demo

Step 1 – Make a new console project

dotnet new console -n ObjectPoolingDemo
cd ObjectPoolingDemo
Code language: JavaScript (javascript)

Step 2 – Replace Program.cs

Open Program.cs in your editor and replace everything with the code from section 1️⃣.

(Optionally replace the autogenerated .csproj with the one in 2️⃣, but not required.)

Step 3 – Build and run in Release

dotnet run -c Release

You’ll see output like:

=========================================
   Object Pooling Demo (ArrayPool<byte>)  
=========================================

Iterations : 1,000,000
BufferSize : 1024 bytes

Warming up JIT (small runs)...
--- Warmup - Without Pooling ---
Iterations: 100,000, BufferSize: 1024 bytes
Time Elapsed : 120 ms
GC Gen0      : 12
GC Gen1      : 1
GC Gen2      : 0
Managed Memory Delta (approx): 3.40 MB
Checksum (ignore, just to keep JIT honest): 123456789

--- Warmup - With Pooling ---
Iterations: 100,000, BufferSize: 1024 bytes
Time Elapsed : 60 ms
GC Gen0      : 2
GC Gen1      : 0
GC Gen2      : 0
Managed Memory Delta (approx): 0.20 MB
Checksum (ignore, just to keep JIT honest): 123456789

=========== REAL TESTS (Release) ==========

--- WITHOUT pooling (new byte[] each time) ---
Iterations: 1,000,000, BufferSize: 1024 bytes
Time Elapsed : 900 ms
GC Gen0      : 100
GC Gen1      : 5
GC Gen2      : 1
Managed Memory Delta (approx): 40.00 MB
Checksum (ignore, just to keep JIT honest): 123456789

--- WITH pooling (ArrayPool<byte>.Shared) ---
Iterations: 1,000,000, BufferSize: 1024 bytes
Time Elapsed : 400 ms
GC Gen0      : 5
GC Gen1      : 0
GC Gen2      : 0
Managed Memory Delta (approx): 2.00 MB
Checksum (ignore, just to keep JIT honest): 123456789
Code language: HTML, XML (xml)

(Exact numbers will differ per machine, but the pattern will be similar.)

4️⃣ How to “Experience” and Interpret the Results

Focus on these lines for each scenario:

1. Time Elapsed
2. GC Gen0 / Gen1 / Gen2
3. Managed Memory Delta (MB)

🔴 Scenario: WITHOUT pooling

• new byte[bufferSize] is executed 1,000,000 times.
• That means ~1,024 * 1,000,000 ≈ 1 GB worth of arrays allocated over time.
• You should see:
  • Higher elapsed time
  • Many more Gen0 collections
  • Possibly some Gen1/Gen2 collections
  • A larger memory delta

This simulates a real-world high-allocation hot path (e.g., per-request/per-message allocations).

🟢 Scenario: WITH pooling (ArrayPool.Shared)

• Arrays are rented and returned from a shared pool.
• Only a small number of underlying arrays are actually allocated.
• Subsequent rents reuse these buffers.

Expected result:

• Lower elapsed time (less GC interference + fewer allocations)
• Much fewer Gen0 collections, often 5–10x fewer
• Gen1/Gen2 collections may drop to 0 or near 0
• Managed Memory Delta much smaller

You are literally seeing GC pressure decreasing because:

• Without pooling → allocate, discard, GC must clean up
• With pooling → allocate a few times, then reuse, GC is mostly idle

5️⃣ Tweaking the Demo to Feel the Effect More

If you want even more dramatic differences:

• Increase iterations (e.g., 5_000_000)
• Or increase bufferSize (e.g., 4096 or 16_384)

const int iterations = 5_000_000;
const int bufferSize = 4096;
Code language: JavaScript (javascript)

⚠️ Be careful: this can make the non-pooled version quite heavy on CPU and memory. Good for a demo on a strong machine, but maybe too much on low-end hardware.

6️⃣ How to Understand in Training

You can summarize for your audience:

“In the no pooling scenario, we allocate a fresh buffer for each iteration, forcing the GC to keep cleaning up.
In the pooling scenario, we reuse buffers from ArrayPool<byte>.Shared, dramatically reducing allocations and GC work.
The difference in GC counts and elapsed time is the direct impact of object pooling.”

Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I have worked at Cotocus. I share tech blog at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow , and SEO strategies at Wizbrand.

Do you want to learn Quantum Computing?

Please find my social handles as below;

Rajesh Kumar Personal Website
Rajesh Kumar at YOUTUBE
Rajesh Kumar at INSTAGRAM
Rajesh Kumar at X
Rajesh Kumar at FACEBOOK
Rajesh Kumar at LINKEDIN
Rajesh Kumar at WIZBRAND

Rajesh Kumar DailyLogs