Why is Creating a Java Thread Considered Expensive?

Why Creating a Thread Is Said to Be Expensive

The creation of a Java Thread is often described as being expensive, but the specific reason behind this notion requires further exploration.

Thread Lifecycle Overhead

The main reason for the perceived expensiveness lies in the complexities involved in thread lifecycle management. Creating and terminating a thread incurs significant time and resources.

• Memory Allocation and Initialization: To create a new thread, a sizable memory block must be allocated for its stack. This stack is initialized with the necessary data structures and information.
• System Calls and Registrations: The operating system must be notified of the new thread's creation through system calls. Various descriptors and data structures are created and registered in both the JVM and the OS.
• Resource Reservation: As long as a thread remains active, it retains dedicated resources such as stack space, references to reachable objects, JVM descriptors, and OS descriptors.

Context Switching

In addition to these overheads, thread creation also introduces context switching costs. When a new thread is created, the JVM must suspend the execution of the current thread and switch to the newly created thread. This context switching incurs additional overhead and can lead to latency in request processing.

Performance Implications

For frequent and lightweight requests, such as in server applications, creating a new thread for each request can consume significant computing resources. It is therefore recommended to consider thread pools or lightweight alternatives to mitigate the costs associated with thread creation.

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