L-1.11: Process Vs Threads in Operating System

Summary

In this 'Gate Smashers' video, the presenter explores the distinctions between processes and threads in a multi-processing, multi-tasking environment. They explain that processes are heavyweight tasks, while threads are more lightweight, ideal for executing the same process multiple times, such as in a print server scenario. The video uses a real-life example to illustrate the concept of creating a child process versus adding an extra 'hand' or thread. It also contrasts the system calls involved in process creation, like 'fork,' with the application-level creation of threads. The presenter highlights the differences in context switching, memory sharing, and the impact of blocking, emphasizing the importance of these concepts for competitive exams.

Takeaways

• 🔑 Processes are heavyweight tasks, whereas threads are lightweight.
• 🌐 Multi-processing and multi-tasking environments allow multiple processes or tasks to run in parallel, often on a single CPU.
• 📚 Multi-threading is useful when the same process is executed multiple times, such as in a print server handling multiple client requests.
• 🤲 Creating a child process involves duplicating the parent process's data, code, stack, and registers, leading to higher overhead.
• 🧩 Threads within a process share the same data and code but have their own stack and registers, reducing overhead.
• 🔄 The fork system call is used to create a child process, which is a clone of the parent, while threads are created at the application level without a system call.
• 🏷️ Operating systems treat each process differently, assigning unique process IDs, but threads are considered part of the same process.
• 🔢 The formula for the maximum number of child processes that can be created is 2^n-1, where n is the number of fork calls.
• 🕒 Context switching between processes is slower due to the need to save and restore more data compared to threads, which share memory and addresses.
• 🚫 Blocking a process does not block its child processes, but blocking a thread can block the entire process as threads are interdependent and share memory.

Q & A

What is the main difference between a process and a thread?

A process is a heavyweight task that includes its own data, code, stack, and registers, whereas a thread is a lightweight task that shares the same data and code with other threads within the same process but has its own stack and registers.

In what kind of environment are processes and threads used?

Processes and threads are used in a multi-processing, multi-tasking environment where multiple tasks run parallel at the same time, often on a single CPU system.

Why might one choose to use multi-threading over creating multiple processes?

Multi-threading might be chosen over multiple processes when the same type of process is running many times, as it reduces overhead by sharing data and code among threads, leading to more efficient resource utilization.

What is a real-life example used in the script to explain the difference between processes and threads?

The script uses the example of moving a duster from one place to another. A process would be like creating a clone to do the task, while a thread would be like creating an extra hand to do the task, illustrating the concept of sharing resources within a single process.

What system call is used to create a child process in a process?

The 'fork' system call is used to create a child process, which is a clone of the existing process, including its own data, code, stack, and registers.

How does the operating system treat processes and threads differently?

The operating system treats each process as a separate entity with its own process ID, while threads within the same process share the same process ID and are considered part of one process.

What is the overhead associated with creating multiple processes?

Creating multiple processes involves an overhead because each process requires its own copy of data, code, stack, and registers, which consumes more resources.

How does context switching differ between processes and threads?

Context switching is slower for processes because it involves saving and loading a large amount of data from the process control block (PCB), whereas switching between threads is faster as they share the same data and code, only requiring a switch of stack and register values.

What happens when a process is blocked in a multi-process environment?

Blocking a process does not affect other processes, as they are independent of each other. Each process can continue running while one is blocked, waiting for I/O operations or other resources.

What is the impact of blocking a thread on the rest of the threads in the same process?

Blocking a thread can block the entire process because threads share the same memory and address space. If one thread is blocked, the operating system may block the entire process, affecting all threads within it.

Why are processes considered independent and threads interdependent?

Processes are considered independent because they have their own resources and do not affect each other when blocked or modified. Threads, on the other hand, are interdependent because they share resources like memory and address space, and changes to one thread can impact the others.