Tell about async/away

Async/await is a concurrency model used in Swift to handle asynchronous operations. It allows functions to be marked as async, indicating that they may suspend execution to wait for an asynchronous operation to complete. When calling an async function, the await keyword is used to denote potential suspension points in the code. This model helps in efficiently managing tasks that involve waiting for operations like disk reads or network requests, by yielding the CPU to other tasks during the wait time.

In Swift, async functions are implemented by keeping their local state on a separate stack from the C stack and splitting them into multiple functions at runtime. This approach ensures that C threads, which are valuable resources, are not blocked unnecessarily, thus optimizing resource usage.

Additionally, Swift introduces the concept of actors, which are reference types that encapsulate shared mutable state and automatically serialize access to their state. This ensures that only one task can execute at a time on an actor, making calls to actor methods from outside their context asynchronous.

For more details, you can refer to the session A Swift Tour: Explore Swift’s features and design (18:33) and Explore Swift performance (24:33).