.NET 8 Runtime & CLR Internals

// .NET thread pool manages a pool of OS threads for async work
// ASP.NET Core: each HTTP request is handled by a thread pool thread
// async/await releases the thread while waiting for I/O — enables high concurrency

// ━━ How async saves threads ━━
// Synchronous (blocks thread pool thread during DB call — bad for scalability):
[HttpGet("sync")]
public IActionResult GetSync()
{
    Thread.Sleep(1000); // thread is BLOCKED — doing nothing, wasting resources
    return Ok("done");
}

// Asynchronous (releases thread during await — frees it for another request):
[HttpGet("async")]
public async Task<IActionResult> GetAsync(CancellationToken ct)
{
    await Task.Delay(1000, ct); // thread RELEASED while waiting
    return Ok("done");
}

// ━━ Thread pool starvation diagnostic ━━
// Symptom: requests queue up even though CPU is low
// Cause: too many synchronous blocking calls (Task.Result, .Wait(), Thread.Sleep)
// Fix: always use async/await end-to-end

// ━━ GC tuning in runtimeconfig.json ━━
// {
//   "configProperties": {
//     "System.GC.Server": true,          // Server GC (default for ASP.NET Core)
//     "System.GC.Concurrent": true,      // Background GC (reduces pause times)
//     "System.GC.HeapHardLimit": 1073741824  // 1GB hard limit (for containers)
//   }
// }