What .NET 10 GC Changes Mean for Developers Overview .NET 10 introduces fundamental changes in garbage collection (GC) that redefine memory management efficiency. These updates include new runtime optimizations, configurable features, and improved developer tooling, aiming to boost performance and reduce memory pressure in modern workloads, especially in cloud-native and microservice architectures. --- Fundamentals of .NET Garbage Collection Generational GC Model Generation 0 (Gen 0): Youngest objects, collected frequently. Generation 1 (Gen 1): Survivors of Gen 0, acts as a buffer. Generation 2 (Gen 2): Long-lived objects like caches/statics. Large Object Heap (LOH/Gen 3): Special handling for objects >85KB. GC cycles perform: Mark: Identify live objects from roots. Relocate: Update references if objects move. Compact: Defragment memory. GC Modes Workstation GC: Default for desktop apps; prioritizes UI responsiveness using fewer threads. Server GC: Used for server apps; parallelizes collection using multiple CPU cores. Configuration example to enable Server GC: Background and Concurrent GC Background collection allows app threads to run while Gen 2 collections happen in parallel. --- Why Generational GC? Generational GC focuses on collecting the youngest objects first, reducing overhead with the trade-off of occasional costly full heap collections when long-lived objects accumulate. --- Evolution of GC in .NET .NET Framework: Introduced generational GC, background collection. .NET Core 1-3: Cross-platform and enhanced server scalability. .NET Core 3.1-6: LOH compaction and container-aware limits. .NET 7-9: Region-based heap management and dynamic heap tuning (DATAS). .NET 10: Major improvements in escape analysis, delegate optimizations, region tuning, DATAS enabled by default. --- New GC Features in .NET 10 Escape Analysis & Stack Allocation: JIT compiler allocates short-lived, non-escaping objects on the stack rather than the heap, reducing GC overhead dramatically. For example, small arrays defined and used locally can bypass heap allocation altogether. | Method | Mean Time (ns) | Allocated Bytes | GC Gen0 Counts | |-------------------------|----------------|-----------------|----------------| | StackallocOfArrays (.NET 9) | 7.7 | 72 B | 0.0086 | | StackallocOfArrays (.NET 10) | 3.9 | 0 B | 0 | DATAS (Dynamic Adaptation to Application Sizes): Automatically tunes heap and GC thresholds to current application memory needs, aggressively releasing unused memory in low-load or containerized environments. Enable by default in .NET 10. Disable via environment variable or runtime config: Region Sizing and Range Tuning: Adjustable virtual address space reservation and region sizes improve efficiency for both small and huge heaps. Delegate Escape Analysis & Closure Optimization: Non-escaping delegates and closures are stack-allocated, reducing memory pressure and invocation costs with roughly 73% less allocation in optimized scenarios. | Version | Mean Time (ns) | Allocated Bytes | Allocation Ratio | |----------|----------------|-----------------|------------------| | .NET 9 | 18,983 | 88 B | 1 | | .NET 10 | 6,292