working set model and page fault frequency

TL;DR

The video explains how the working set model helps prevent thrashing in computer systems by determining actively used pages based on recent references.

Transcript

click the Bell icon to get latest videos from akira hello friends today we are going to discuss a possible therapy for thrashing is known as a working set model how a working set size be prevents from the thrashing and how it is implemented actually in the page reference stream what are the advantages and disadvantages of having a working set model... Read More

Key Insights

• 😒 The working set model is based on the assumption of locality and uses the parameter delta to determine actively used pages.
• 🥺 Choosing the appropriate working set size is crucial, as a small size may miss important pages, and a large size may lead to overlapping localities.
• 😫 Allocation of frames is based on the working set size, with the operating system examining working set models and allocating frames accordingly.
• 🖼️ Thrashing can occur if the total demand for frames exceeds the available frames, and suspending a process and reallocating frames helps prevent thrashing.
• ✋ A direct approach to preventing thrashing is using page fault frequency, where higher page faults indicate higher levels of thrashing.

Questions & Answers

Q: What is the working set model and how does it prevent thrashing?

The working set model is a therapy for thrashing that determines actively used pages by examining the most recent delta references. It prevents thrashing by distinguishing between actively used and unused pages.

Q: How does the working set size affect the prevention of thrashing?

The working set size is crucial in preventing thrashing. If it's too small, it may not encompass the entire locality, and if it's too large, it may overlap multiple localities, leading to ineffective prevention of thrashing.

Q: How is the working set size determined and frames allocated?

The operating system examines the working set models of every system and allocates frames based on the working set size. It allocates frames to each process's working set based on the delta references and ensures the working set size does not exceed the total number of available frames in the system.

Q: How does the working set strategy prevent thrashing?

The working set strategy prevents thrashing by helping level the multi-programming degree. It ensures that the number of frames matches the actual degree of multi-programming, preventing both overallocation and underallocation of frames.

Summary & Key Takeaways

• The working set model is a therapy for preventing thrashing in computer systems, based on the assumption of locality and the use of a parameter called delta.

• The working set size is determined by examining the most recent delta references and distinguishing actively used pages from those not in use.

• If the working set size is too small or too large, it may not encompass the entire locality or overlap multiple localities, respectively.