Abstract
- A fixed-number group of Thread that are reused to execute tasks submitted to Task Queue by a client. The number of Thread is usually the number of cores the system has. Less will lead to wasted CPU power, more will introduce Context Switch which has overhead, unless the task isn’t cpu-bounded
- Commonly used in scenarios where tasks are small, numerous, and independent(stateless). Examples include web servers handling HTTP requests and applications that perform many asynchronous I/O operations
Reduced Overhead
Creating a new thread is an expensive operation, so reusing threads can improve performance. Especially for Kernel Thread.
Improved Resource Management
A thread pool limits the number of Thread that can be active at any one time. This ensures the system does not become overwhelmed with too many concurrent threads, which can reduce performance due to Context Switch or resource thrashing.
Task Queue
- Tasks that need to be executed are placed in a queue
- When a Thread becomes available, it pulls a task from the queue and executes it
- After completing the task, the thread returns to the pool to await the next assignment
Thread Safety
Make sure the Task Queue is manipulated by one Thread at a time. Otherwise, we may we may have more than 1 thread processing the same task - Race Condition (竞态条件) happens. Thus, we need to have Mutex (互斥体) on the Task Queue.
Efficient assignment of task
Make sure idle Threads don’t keep checking Task Queue for tasks. This will result in purely wasted computation.