Heap allocations aren’t entirely bad, but when an object is allocated on a heap, it contributes to the garbage collection cycles, which in turn reduces overall application performance.
Introduction
One approach to optimizing resource usage in async code is by using ValueTask<TResult> syntax to minimize heap allocations, which in turn reduces pressure on garbage collection and enhances overall performance.
Learning Objectives
- The Problem with Heap Allocations
- Optimizing with ValueTask<TResult>
- When to Use ValueTask<TResult>
Prerequisites for Developers
- Basic understanding of C# programming language.
Getting Started
Heap allocations aren’t entirely bad, but when an object is allocated on a heap, it contributes to the garbage collection cycles, which in turn reduces overall application performance. In the case of excessive heap allocation, the garbage collector can cause GC pauses.
Bad Practice: Excessive Use of Task<TResult>
Let’s consider a common asynchronous pattern that developers commonly use:
public async Task<string> ReadDataAsync()
{
var data = await ReadFromStreamAsync(_stream);
return ProcessData(data);
}
If the above-mentioned method is called more frequently, each request results in a new Task instance being allocated on heap memory. Over time, it leads to increased garbage collection overhead.
Optimizing with ValueTask<TResult>
By changing the return type from Task<TResult> to ValueTask<TResult>, we can reduce heap allocations
public async ValueTask<string> ReadDataAsync()
{
var data = await ReadFromStreamAsync(_stream);
return ProcessData(data);
}
The aforementioned optimization is beneficial for high-frequency async operations or methods that are expected to complete synchronously in a significant portion of time.
When to Use ValueTask<TResult>
- High-frequency methods
- Performance-sensitive code
- Methods that often complete synchronously
Create another class named TaskVsValueTask and add the following code snippet
public static class TaskVsValueTask
{
public static async Task<string> FetchDataAsync()
{
// Simulate a delay to mimic fetching data
await Task.Delay(1000);
return "Data fetched using Task";
}
public static async ValueTask<string> FetchDataValueTaskAsync()
{
// Simulate a delay to mimic fetching data
await Task.Delay(1000); // Note: Use Task.Delay for the sake of example.
return "Data fetched using ValueTask";
}
}
Execute from the main method as follows
#region Day 20: Task vs. Value Task
static async Task<string> ExecuteDay20()
{
Console.WriteLine("Fetching data with Task...");
string result = await TaskVsValueTask.FetchDataAsync();
Console.WriteLine(result);
Console.WriteLine("Fetching data with ValueTask...");
string resultValueTask = await TaskVsValueTask.FetchDataValueTaskAsync();
Console.WriteLine(resultValueTask);
return "Executed Day 20 successfully..!!";
}
#endregion
Console Output
Fetching data with Task...
Data fetched using Task
Fetching data with ValueTask...
Data fetched using ValueTask
Complete Code on GitHub
GitHub — ssukhpinder/30DayChallenge.Net
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