How does cooperative thread pool work?

The cooperative thread pool in Swift is designed to manage concurrency efficiently by allowing tasks to yield the CPU when they are waiting for asynchronous operations to complete. This is achieved through the use of async functions and tasks, which are the fundamental units of concurrency in Swift.

Here are some key points about how cooperative thread pools work in Swift:

Tasks and Async Functions: Tasks represent independent concurrent execution contexts and are lightweight, allowing for the creation of many tasks. Async functions are split into multiple partial functions at runtime, which handle different parts of the function around suspension points (e.g., await).
Memory Management: Async functions allocate memory on an async stack, which is different from the C stack. This stack is managed in slabs, and memory is allocated from these slabs as needed. If a slab is full, a new one is allocated.
Suspension and Resumption: When a task performs an asynchronous operation, it suspends and yields the CPU to other tasks. This allows other tasks to run while the original task is waiting for the async operation to complete. Once the async operation completes, the task resumes execution.
Actors: Actors in Swift help manage shared mutable state by serializing access to their state, ensuring that only one task can execute on an actor at a time. This helps prevent data races and makes concurrent programming safer.

For more detailed information, you can refer to the session Explore Swift performance (24:33).

Relevant Sessions

These sessions provide a comprehensive overview of concurrency in Swift, including the cooperative thread pool, async functions, and actors.