Multithreading vs Multiprocessing in Operating System

Multiprocessing and Multithreading both increase a system’s computing power. A multiprocessing system comprises multiple processors whereas multithreading comprises multiple threads. Learn multithreading vs multiprocessing in OS.

Multiprocessing in OS

A system that comprises more than two processors is called a multiprocessing system. These additional CPUs help increase the computing speed of the system. Despite sharing a system, each CPU has its own registers and main memory. Processors share processes and resources amongst themselves dynamically so that no processor may sit idle or get overloaded.

Characteristics of Multiprocessing in OS

Following are some characteristics of Multiprocessing:

• Classification in multiprocessing depends on the way their memory is organized.
• Improves system reliability.
• Improves system performance by decomposing programs into parallel executable tasks.

Advantages of Multiprocessing in Operating System

Following are the advantages of Multiprocessing:

• More work can be done in a shorter time period.
• Straightforward code.
• Multiple CPU & cores are an additional advantage.
• Helps avoid GIL limitations for CPython.
• Removes synchronization primitives unless shared memory is used.
• Interruptible/killable child processes.
• Efficient when a large volume of data processes at a very high speed.
• Cost-efficient as processors share peripherals and power supplies.

Disadvantages of Multiprocessing in OS

Following are the disadvantages of multiprocessing OS:

• Increased overhead complicates Inter-Process Communication.
• Larger memory footprint.

Multithreading in Operating System

A program execution technique in which a process can have multiple code segments (like threads) is known as multithreading. It runs concurrently within the context of a process i.e., in a multi-threaded application two or more threads run concurrently. This is why multithreading is also known as concurrency.

Characteristics of OS Multithreading

Following are the characteristics of multithreading:

• Each thread runs parallel to each other.
• Since threads don’t allow the separation of the memory area, the program achieves better application performance. This also saves memory.

Advantages of OS Multithreading

Following are the advantages of multithreading:

• Threads share the same address space.
• Threads are lightweight and have a low memory footprint.
• Communication between threads is cost-efficient.
• It is easy to access memory states from another context.
• Helps make responsive UIs.
• Good for I/O-bound applications.
• It takes less time to terminate and switch between two threads of the same process.
• Threads start and switch tasks faster.
• All Threads share a process memory pool.
• Thread creation takes lesser time in an existing process as compared to a new process

Disadvantages of OS Multithreading

Following are the disadvantages of multithreading OS:

• Not interruptible/killable
• Manual use of synchronization is necessary when it doesn’t follow a command queue and message pump model.
• Code is harder to understand and increases the possibility for race conditions.

Multiprocessing vs Multithreading in Operating System

Parameter	Multiprocessing	Multithreading
Basic	helps increase computing power	helps create computing threads for a single process which in turn increases computing power.
Execution	Allows the execution of  multiple processes concurrently	threads of a single process execute concurrently
CPU switching	Here CPU switches between multiple programs giving an illusion that multiple programs are running simultaneously	Here CPU switches between multiple threads giving an illusion that all threads are running simultaneously
Creation	Process creation is slow and resource-specific	Thread creation is time and resource economical
Classification	Two types: symmetric and asymmetric	No classification
Memory	Each process and program has a separate memory and resources	All threads of the same process share the same memory and resources
Pickling objects	Avoids pickling	Relies on pickling objects in memory to send to other processes
Program	Allows execution of multiple programs and tasks	Executes multiple threads of the same/different processes.
Time Taken	Job processing takes less time	Job processing takes a moderate amount of time

Summary

Multiprocessing and Multithreading both increase a system’s computing power. A system that comprises more than two processors is called a multiprocessing system. A program execution technique in which a process can have multiple code segments (like threads) is known as multithreading.