Allocation of Frames in Operating Systems

This article discusses the allocation of frames in operating systems. It covers two main algorithms for frame allocation: equal allocation and proportional allocation. It also discusses the concepts of global and local replacement, and thrashing.

Questions

1. What is the formula for proportional allocation of frames?
2. What is the difference between global and local replacement?
3. What is thrashing?

Answers

1. The formula for proportional allocation of frames is:

   “`
   ai = (si / S) * m

   where `ai` is the number of frames allocated to process `i`, `si` is the size of process `i`, `S` is the total size of all processes, and `m` is the number of frames in the system.

2. Global replacement means that any process can take a frame from any other process. Local replacement means that each process can only take frames from its own set of allocated frames.
3. Thrashing is a situation where a process is constantly swapping pages in and out of memory. This can happen if a process does not have enough frames, or if the page-fault rate is very high.