Asynchronous
Each task execute until it would block, then switching to another task that is ready to make progress.
Green threads and async are related but not same concepts. Green threads, runtime does M:N thread scheduling over OS Threads
Model runs larger number of tasks on a limited number of threads, because the per-task overhead is typically very low.
Eg: I/O-bound tasks(Network or file I/O)
Async vs Threading
| Async | Threading | |
|---|---|---|
| Concurrency | Uses event loops/epoll() | Executing multiple threads of execution concurrently or parallely. |
| Resource Overhead | lower resource overhead compared to multithreading. Since reduces context-switching and memory overhead | High resource overhead. Since each thread has its own stack and context |
| Complexity | Simpler for certains cases like I/O-bound operations bcoz avoids deadlocks, race conditions | More complex since it involves race conditions, deadlocks, and other concurrency issues |
| Performance | Better performance for I/O-bound applications. Not suited for CPU-bound tasks. | Better performance for CPU-bound tasks |