FANG Interview Question | Process vs Thread

Summary

This video explains the difference between processes and threads, common topics in technical interviews. A process is an executing program with its own memory space, ensuring isolation and stability. Threads are units of execution within a process, sharing the same memory space, which allows for efficient communication but also risks bringing down the entire process if one thread fails. The video also discusses the concept of context switching, its cost, and mechanisms like fibers and coroutines to reduce these costs. It concludes with a brief mention of system design resources.

Takeaways

• 💡 A program is an executable file that contains code stored as a file on disk.
• ⚙️ When a program's code is loaded into memory and executed by the processor, it becomes a process.
• 🔄 An active process includes resources like processor registers, program counters, stack pointers, and memory pages, managed by the operating system.
• 🔒 Each process has its own memory address space, preventing one process from corrupting another's memory.
• 🌐 Chrome uses process isolation, running each tab in its own process, so one tab's issues don't affect others.
• 🧵 A thread is the unit of execution within a process, and a process has at least one thread called the main thread.
• 📚 Threads within a process share the same memory address space, enabling communication via shared memory.
• ⚠️ One misbehaving thread can bring down the entire process, unlike isolated processes.
• 🔄 Context switching allows the operating system to switch between processes or threads, but it is resource-intensive.
• 🚀 Switching context between threads is generally faster than between processes because threads share memory, reducing the need for memory page switching.

Q & A

What is a program in the context of computing?

A program is an executable file that contains a set of processor instructions stored as a file on disk, which when loaded into memory and executed by the processor, becomes a process.

What happens when a program's code is loaded into memory and executed?

When a program's code is loaded into memory and executed, it becomes a process, which also includes the resources needed for the program to run, managed by the operating system.

What are some of the resources managed by the operating system for an active process?

Resources managed by the operating system for an active process include processor registers, program counters, stack pointers, and memory pages assigned for the process's heap and stack.

Why is each process having its own memory address space important?

Each process having its own memory address space is important because it prevents one process from corrupting the memory space of another, ensuring that a malfunction in one process does not affect others.

Can you give an example of how process isolation is utilized in modern software?

An example of process isolation is Google Chrome, which runs each tab in its own process, ensuring that if one tab misbehaves, other tabs remain unaffected.

What is a thread in relation to a process?

A thread is the unit of execution within a process. A process has at least one thread, known as the main thread, and can have multiple threads for concurrent execution.

How do threads within a process differ from processes themselves?

Threads within a process share the same memory address space and have their own stack, whereas processes have separate memory address spaces and manage their own resources.

What is the consequence of one misbehaving thread within a process?

A misbehaving thread within a process can bring down the entire process because threads share the same memory space and resources.

How does the operating system manage running threads or processes on a CPU?

The operating system manages running threads or processes on a CPU through context switching, which involves saving the state of the current process and loading the state of another process to run.

Why is context switching considered expensive in terms of system resources?

Context switching is considered expensive because it involves saving and loading registers, switching memory pages, and updating kernel data structures, which can be a time-consuming process.

What are fibers and coroutines, and how do they relate to context switching?

Fibers and coroutines are mechanisms that aim to minimize the cost of context switching by allowing for cooperative scheduling, where the application itself handles task scheduling and must yield control periodically to allow other tasks to run.

What advice is given for applications that use fibers or coroutines?

Applications using fibers or coroutines must ensure that long-running tasks are broken up by yielding control periodically to prevent blocking other tasks from executing.