Does multithreading always yield better performance than single threading?

Question

I know the answer is No, here is an example Why single thread is faster than multithreading in Java? .

So when processing a task in a thread is triv

Answer 1

There are 2 scenarios that can happen here :

1. MultiThreading on Single Core CPU :

   1.1 When to use : Multithreading helps when tasks that needs parallelism are IO bound.Threads give up execution while they wait for IO and OS assign the time slice to other waiting threads. Sequential execution do not have the behavior - Multithreads will boost the performance.

   1.2 When Not to Use : When the tasks are not IO bound and mere a calculation of something, you might not want to go for multi threading since thread creation and context switching will negate the gain if any. - Multithreads will have least impact.

2. MultiThreading in Multi Core CPU : Multi core can run as many threads as the number of core in CPU. This will surely have performance boost. But Running higher number of threads than the available cores will again introduce the thread context switching problem. - Multithreads will surely have impact.

Be aware : Also there is limit on adding/introducing number of threads in system. More context switches will negate overall gain and application slows down.