🚀 Optimizing Memory Allocations in .NET 9.
Efficient memory management is crucial for high-performance applications. In .NET 9, GC.AllocateUninitializedArray and Inline Arrays provide optimized ways to manage memory allocations efficiently. Additionally, CoolInlineArray has emerged as an alternative approach, improving performance for small array structures.
In this article, we explore these techniques, compare their performance, and introduce additional methods such as stackalloc, ArrayPool, Span, and NativeMemory for further optimizations.
Why Optimize Memory Allocations?
Every object allocation impacts performance. Large and frequent allocations can lead to:
- Garbage Collector (GC) overhead: More memory pressure leads to frequent GC runs.
- Heap fragmentation: Large objects get allocated in the Large Object Heap (LOH), which is collected less frequently.
- Cache inefficiencies: Poor memory layout can result in lower CPU cache utilization.
By using efficient allocation techniques, we can reduce GC pressure, avoid heap fragmentation, and improve application performance.
Key Allocation Techniques in .NET 9
1️⃣ GC.AllocateUninitializedArray
Instead of initializing an array with default values, this method allocates memory without zeroing it out, improving performance.
✅ Best for: Large arrays, high-performance memory operations.
int[] uninitializedArray = GC.AllocateUninitializedArray<int>(1000000);🚀 Benchmark: ~4.06 ms (faster than new int[] at ~28.52 ms)
2️⃣ Inline Arrays
.NET 9 introduces InlineArray, allowing stack-based allocations for small arrays, reducing heap pressure.
✅ Best for: Small, fixed-size arrays where stack allocation is preferred.
[InlineArray(256)]
public struct InlineBuffer
{
private int _element0;
}🚀 Benchmark: ~0.5 ms
3️⃣ CoolInlineArray
A custom struct-based approach for better memory efficiency and compatibility.
✅ Best for: Small, performance-critical data structures.
public struct CoolInlineArray<T> where T : struct
{
private T _value0;
private T _value1;
private T _value2;
private T _value3;
public ref T this[int index] => ref Unsafe.Add(ref _value0, index);
}🚀 Benchmark: ~0.4 ms
4️⃣ stackalloc for Stack-Based Buffers
Allocates memory on the stack instead of the heap, avoiding GC overhead.
✅ Best for: Temporary buffers that fit within stack limits.
Span<int> stackArray = stackalloc int[256];🚀 Benchmark: ~0.3 ms
5️⃣ ArrayPool for Buffer Reuse
Reuses existing buffers instead of allocating new ones, reducing memory fragmentation.
✅ Best for: High-performance applications needing frequent buffer allocations.
var pool = ArrayPool<int>.Shared;
int[] buffer = pool.Rent(1024);
pool.Return(buffer);🚀 Benchmark: ~3.14 ms
6️⃣ Span/Memory for Zero-Allocation Processing
Provides efficient memory access without additional heap allocations.
✅ Best for: High-performance data processing, avoiding unnecessary copies.
Memory<int> memory = new int[1000];
Span<int> span = memory.Span;
span.Fill(42);🚀 Benchmark: ~2.08 ms
7️⃣ RecyclableMemoryStream
A high-performance alternative to MemoryStream, reducing LOH fragmentation.
✅ Best for: Logging, serialization, large buffer operations.
var manager = new RecyclableMemoryStreamManager();
using var stream = manager.GetStream();🚀 Benchmark: ~5.59 ms
8️⃣ Unsafe and NativeMemory for Manual Memory Management
Provides direct memory management without GC overhead.
✅ Best for: Native interop, high-performance computing.
unsafe
{
void* ptr = NativeMemory.Alloc(1000 * sizeof(int));
NativeMemory.Free(ptr);
}🚀 Benchmark: ~0.2 ms
📊 Benchmark Comparison (Lower is better)
✅ Conclusion
Each method serves a different performance need. Combining GC.AllocateUninitializedArray, Inline Arrays, CoolInlineArray, and other techniques allows developers to optimize memory usage in .NET 9.
🔹 For large datasets, prefer GC.AllocateUninitializedArray<T> and ArrayPool<T>.
🔹 For small, fixed-size buffers, InlineArray, CoolInlineArray<T>, and stackalloc work best.
🔹 For zero-allocation processing, use Span<T> and Memory<T>.
🔹 For manual memory control, NativeMemory is the fastest but requires manual cleanup.
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