Differences Between Processes and Threads and Their Communication Mechanisms

Process and Thread Differences

For a process, a child process is a copy of its parent, inheriting the parent’s data space, heap, and stack.

A thread, in contrast, is a more execution‑oriented entity that can directly share data with other threads in the same process while having its own stack and execution sequence.

Both improve concurrency, program efficiency, and response time, but each has trade‑offs: threads have lower overhead but are harder to manage and protect, whereas processes have higher overhead but better isolation. Threads run well on SMP machines, while processes can be migrated across machines.

The fundamental distinction is that each process has its own address space, whereas threads share a common address space; all other differences stem from this.

Speed – threads are created quickly, communicate fast, and switch rapidly because they share the same address space.

Resource utilization – threads make better use of resources.

Synchronization – threads need synchronization mechanisms when accessing shared variables, while processes do not.

Consequently, the way they communicate also differs for the same reason.

Differences in Communication Methods

Because threads share an address space, they do not need explicit communication, only proper synchronization/mutual exclusion to protect shared global variables.

Inter‑process communication (IPC) such as signals, pipes, or shared memory is provided by the operating system as system calls.

1. Inter‑Process Communication Methods

Pipe (pipe)

A pipe is a half‑duplex communication channel that allows one‑way data flow and can only be used between related processes (typically parent‑child).

Named Pipe (named pipe)

A named pipe is also half‑duplex but permits communication between processes without a parent‑child relationship.

Semaphore (semaphore)

A semaphore is a counter used to control access to shared resources, acting as a lock to prevent concurrent access by multiple processes or threads.

Message Queue (message queue)

A message queue stores messages in the kernel, identified by a queue identifier, overcoming the limitations of signals and pipes such as limited data and fixed buffer sizes.

Signal (signal)

A signal is a more complex IPC mechanism used to notify a receiving process that a specific event has occurred.

Shared Memory (shared memory)

Shared memory maps a memory segment that multiple processes can access; it is the fastest IPC method and is often combined with other mechanisms like signals for synchronization.

Socket (socket)

A socket provides a communication mechanism that can be used between processes on different devices.

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2. Thread Communication Methods

Lock mechanisms: mutex, condition variable, read‑write lock

Mutex provides exclusive access to prevent concurrent modifications of data structures.

Read‑write lock allows multiple threads to read shared data simultaneously while writes are exclusive.

Condition variables block a thread until a specific condition becomes true, always used together with a mutex.

Semaphore mechanisms (Semaphore): unnamed and named thread semaphores

Signal mechanisms (Signal): similar to process‑level signal handling

Thread communication primarily serves synchronization purposes; unlike processes, threads do not have dedicated data‑exchange mechanisms.

Thank you for reading, hope it helped :) Source: blog.csdn.net/liyue98/article/details/80112246