What is thread vs process?

Process means a program is in execution, whereas thread means a segment of a process. A Process is not Lightweight, whereas Threads are Lightweight. A Process takes more time to terminate, and the thread takes less time to terminate. Process takes more time for creation, whereas Thread takes less time for creation.

What is the difference between a thread and a process?

A thread shares information like data segment, code segment, files etc. with its peer threads while it contains its own registers, stack, counter etc. A process is a program under execution i.e an active program. A thread is a lightweight process that can be managed independently by a scheduler.

Is it better to use threads or processes?

You'd prefer multiple threads over multiple processes for two reasons: Inter-thread communication (sharing data etc.) is significantly simpler to program than inter-process communication. Context switches between threads are faster than between processes.

Why thread is faster than process?

a process: because very little memory copying is required (just the thread stack), threads are faster to start than processes. To start a process, the whole process area must be duplicated for the new process copy to start.

How many threads can a core have?

Each CPU core can have two threads. So a processor with two cores will have four threads. A processor with eight cores will have 16 threads. A processor with 24 cores (yes, those exist), will have 48 threads.

Difference Between Process and Thread - Georgia Tech - Advanced Operating Systems

What thrashing means?

Thrashing occurs when there are too many pages in memory, and each page refers to another page. The real memory shortens in capacity to have all the pages in it, so it uses 'virtual memory'.

Can a process have 0 threads?

A processor executes threads, not processes, so each application has at least one process, and a process always has at least one thread of execution, known as the primary thread. Though it does go on to say: A process can have zero or more single-threaded apartments and zero or one multithreaded apartment.

Why process is heavyweight?

Processes are heavyweight operations. Threads are lighter weight operations. Each process has its own memory space. Threads use the memory of the process they belong to.

Is heap shared between processes?

Every process can use heap memory to store and share data within the process. We have a rule in programming whenever we take some space in heap memory, we need to release it once job is done, else it leads to memory leaks.

Can processes share memory?

Yes, two processes can both attach to a shared memory segment. A shared memory segment wouldn't be much use if that were not true, as that is the basic idea behind a shared memory segment - that's why it's one of several forms of IPC (inter-Process communication).

What is deadlock OS?

A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function. The earliest computer operating systems ran only one program at a time.

Do threads share memory?

In a multi-threaded process, all of the process' threads share the same memory and open files. Within the shared memory, each thread gets its own stack. Each thread has its own instruction pointer and registers.

Can a dead thread be invoked?

Once the thread completes its run() method and dead, it cannot be brought back to thread of execution or even to runnable state. Invoking start() method on a dead thread causes runtime exception.

What is virtual memory in OS?

Virtual memory is a common technique used in a computer's operating system (OS). Virtual memory uses both hardware and software to enable a computer to compensate for physical memory shortages, temporarily transferring data from random access memory (RAM) to disk storage.

What is swapping in operating system?

Swapping is a mechanism in which a process can be swapped temporarily out of main memory (or move) to secondary storage (disk) and make that memory available to other processes. At some later time, the system swaps back the process from the secondary storage to main memory.

What is page fault frequency?

The page fault frequency (PFF) algorithm adapts to dynamic changes in program behavior during execution. Therefore its performance is expected to be less dependent on prior knowledge of the program behavior during execution.

What is a stack vs heap?

Stack is a linear data structure whereas Heap is a hierarchical data structure. Stack memory will never become fragmented whereas Heap memory can become fragmented as blocks of memory are first allocated and then freed. Stack accesses local variables only while Heap allows you to access variables globally.

Do threads use virtual memory?

Yes. Each thread has its own stack, but all the memory associated with the process is in the same virtual address space. If a function in one thread had a pointer to a stack-allocated variable in another thread, that function could read from/write to that variable.

Is code shared between threads?

Threads are not independent of one another like processes are, and as a result threads share with other threads their code section, data section, and OS resources (like open files and signals). But, like process, a thread has its own program counter (PC), register set, and stack space.

What are the 4 conditions of deadlock?

The four necessary conditions for a deadlock situation are mutual exclusion, no preemption, hold and wait and circular set.

What is no preemption?

No preemption: a resource can be released only voluntarily by the process holding it. Circular wait: each process must be waiting for a resource which is being held by another process, which in turn is waiting for the first process to release the resource.

What is CPU scheduling?

CPU Scheduling is a process of determining which process will own CPU for execution while another process is on hold. The main task of CPU scheduling is to make sure that whenever the CPU remains idle, the OS at least select one of the processes available in the ready queue for execution.

Why do we need threads?

Threads are very useful in modern programming whenever a process has multiple tasks to perform independently of the others. This is particularly true when one of the tasks may block, and it is desired to allow the other tasks to proceed without blocking.

What is the difference between UMA and NUMA?

In UMA, Uniform Memory Access, a single memory controller is used and it is applicable for general purpose applications and time sharing applications. In NUMA, Non-Uniform Memory Access, multi memory controllers are used. NUMA is suitable for real-time applications and time critical applications.