The 30-Day .NET Challenge - Day 22: Use Array Pool

ArrayPool<T>, a mechanism to recycle temporary buffers and optimize performance by reducing garbage collection cycles.

Introduction

Frequent allocation and deallocation of bigger buffers can impact performance due to the increased work on the garbage collector. The recommendation is to use ArrayPool<T>, a mechanism to recycle temporary buffers and optimize performance by reducing garbage collection cycles.

Learning Objectives

• Understanding the Problem with Traditional Buffer Allocation
• The Approach Using ArrayPool<T>
• Best Practices for Using ArrayPool<T>

Prerequisites for Developers

• Basic understanding of C# programming language.

30 Day .Net Challenge

Getting Started

Understanding the Problem with Traditional Buffer Allocation

A common approach developers use involves directly allocating a new buffer

// Allocating a new large buffer
byte[] buffer = new byte[4096];

While the aforementioned code snippet looks clean and straightforward, it has significant drawbacks regarding performance, particularly in applications that frequently request large temporary buffers. Each allocation will increase the heap size, leading to more frequent garbage collection.

The Approach Using ArrayPool<T>

ArrayPool<T> is part of the System.Buffers namespace and provides temporary arrays, thereby reducing the need for frequent memory allocations and GC.

// Using ArrayPool<T> to recycle large buffers
var pool = ArrayPool<byte>.Shared;
byte[] buffer = pool.Rent(4096);
try
{
    // Work with the buffer
}
finally
{
    pool.Return(buffer);
}

Best Practices for Using ArrayPool<T>

While ArrayPool<T> can significantly enhance performance, there are best practices to ensure its effective use:

• Properly Return Buffers: Always return the rented buffers to the pool in a final block to ensure that they are returned even if an exception occurs.
• Clear Buffers When Necessary: If sensitive data is stored in the buffer, use the overload of the Return method that takes a boolean parameter indicating whether the buffer should be cleared.
• Avoid Holding Buffers for Long Periods: Rent buffers for the shortest time necessary to keep the pool efficient and avoid exhausting the pool.

Complete Code

Create another class named ArrayPoolExample and add the following code snippet.

public static class ArrayPoolExample
{
    public static void BadMethod()
    {
        // Allocating a new large buffer
        byte[] buffer = new byte[4096];
        // Simulate work with the buffer
        FillBuffer(buffer, 0xAA); // Example operation
        Console.WriteLine("Buffer used and will be discarded after method execution.");
    }

    public static void GoodMethod()
    {
        var pool = ArrayPool<byte>.Shared;
        byte[] buffer = pool.Rent(4096);
        try
        {
            // Work with the buffer
            FillBuffer(buffer, 0xBB); // Example operation
            Console.WriteLine("Buffer rented from the pool and returned after use.");
        }
        finally
        {
            pool.Return(buffer);
        }
    }

    public static void FillBuffer(byte[] buffer, byte value)
    {
        for (int i = 0; i < buffer.Length; i++)
        {
            buffer[i] = value;
        }
        // Just an example to simulate buffer usage
        Console.WriteLine($"Buffer filled with value: {value}");
    }
}

Execute from the main method as follows.

#region Day 22: Array Pool
static string ExecuteDay22()
{

    Console.WriteLine("Demonstrating BAD Method:");
    ArrayPoolExample.BadMethod();
    Console.WriteLine("\nDemonstrating GOOD Method:");
    ArrayPoolExample.GoodMethod();
    return "Executed Day 22 successfully..!!";
}

#endregion

Console Output

Demonstrating BAD Method:
Buffer filled with value: 170
Buffer used and will be discarded after method execution.

Demonstrating GOOD Method:
Buffer filled with value: 187
Buffer rented from the pool and returned after use.

Complete Code on GitHub

GitHub — ssukhpinder/30DayChallenge.Net

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