Question

Operating Systems

Multithreading provides a way for improving the performance of applications. Is it guaranteed that all multithreaded applications perform better their corresponding single threaded application? Using examples, prove that this is not always true.

Answer 1

Thread:
In a program, a thread is a way that divides the program into more than one concurrently executing task. Thread is a lightweight process and one process can have multiple threads. A thread has its own Process Control Block like a process.

Advantages of thread in a program:

• A thread concept utilizes the multiprocessor system very effectively because we can schedule multiple threads on multiple processors.
• Simultaneous access to multiple applications because the context switching time between two threads is less as compared to the process.
• Thread help to maintain a responsive user interface because a threading system is more responsive. Threads are the lightweight process and it minimizes the use of system resources.
• Parallelism is achieved by using the thread concept because threads are executed concurrently.

It is not always guaranteed that multithreaded applications perform better their corresponding single-threaded application because if more than one thread is requesting for the same resources in a circular way then a deadlock may occur.

Starvation:

Starvation is a situation when a low priority process in ready queue is waiting for the CPU for a long time and other high priority processes are assigned to the CPU.

Deadlock:

Deadlock is a situation in the operating system where each of the running processes is waiting for a certain resource that is held by another running process in a circular wait for an infinite time.

For example:

P1: Request for resource R1 to get this.

P2: Request for resource R2 and get this.

P1: Request for resource R2 to and goes in the waiting state.

P2: Request for resource R1 and goes in the waiting state.

P1 is waiting for the resource R2 but it holds by the P2 and P2 is waiting for the R1 but it is held by the P1. Both of the processes are waiting for each other to release the resources but there is no preemption.

So, if the deadlock will occur then the system performance will degrade.