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 optimize resource usage in async code is by using ValueTask 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
When to Use ValueTask
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 case of excessive heap allocation, the garbage collector can lead to GC pauses.
Bad Practice: Excessive Use of Task
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
By changing the return type from Task to ValueTask, 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 which are expected to complete synchronously in a significant portion of time.
When to Use ValueTask
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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