Question

We know that a memory can suffer from Thrashing.

(a) Define the working set of a process.

(b) Define memory thrashing.

(c) If a system suffers from thrashing, how can we try to fix the problem to reduce thrashing? (your suggested solution can be by making change to the OS or hardware).

Answer 1

Solution:
a)Working set of a process.
Every process has some assocaited pages in the memory and they gets loaded via Demand paging.
All the pages may not be required at all times and hence, page in demand is loaded.
Following above different processes requires different pages to be loaded while execution.

b) Define memory thrashing.
There are specifications of each system and type of application that gets loaded in the memory.
Heavy applications requires specifications accordingly. However, if above is not handled properly
then CPU will spend time only in managing page faults, which in turn increases time for process
completion. This is known as thrashing.

c) Suggestions to reduce thrashing.
There are two causes due to which thrashing occurs.
1. High Degree of multi-programming.
2. Lack of frames.

Solution #1 Locality concept
If there are enough frames for any process to complete its execution, then thrashing can be avoided.

Solution#2 Page fault frequency
As the page fault rate changes add or remove frames for the processes. IF page fault are high,
allocates more frames. Similarly, if page fault is low remove some frames.

Above are two concepts implementated to reduce thrashing.