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Questions and Answers
What is the first action the operating system takes when a page fault occurs?
What is the first action the operating system takes when a page fault occurs?
- Resume the process immediately
- Initiate disc IO immediately
- Find a free page frame (correct)
- Update the page table
What does the operating system do after allocating a free page frame?
What does the operating system do after allocating a free page frame?
- Updates all page tables of running processes
- Locks the memory to prevent further page faults
- Immediately resumes the process that incurred the fault
- Initiates disc IO to move the page from virtual memory (correct)
What action does the operating system take upon completion of the disc IO?
What action does the operating system take upon completion of the disc IO?
- It runs a diagnostic check
- It updates the page table (correct)
- It forces a garbage collection
- It powers off the system
What is one reason the operating system overcommits its available physical memory?
What is one reason the operating system overcommits its available physical memory?
When does the operating system run a page replacement algorithm?
When does the operating system run a page replacement algorithm?
What happens to the process that incurred a page fault after the page table is updated?
What happens to the process that incurred a page fault after the page table is updated?
What is a potential analogy used to describe operating system's memory management strategy?
What is a potential analogy used to describe operating system's memory management strategy?
What occurs after the page has been retrieved from storage into the allocated page frame?
What occurs after the page has been retrieved from storage into the allocated page frame?
What is a limitation of operating systems regarding page replacement algorithms?
What is a limitation of operating systems regarding page replacement algorithms?
What can enhance the efficiency of page replacement in operating systems?
What can enhance the efficiency of page replacement in operating systems?
In addition to page replacement, what other aspect of the operating system can be customized?
In addition to page replacement, what other aspect of the operating system can be customized?
Why might an operating system's default algorithm for page replacement not always be effective?
Why might an operating system's default algorithm for page replacement not always be effective?
What factor influences how an operating system can customize page replacement algorithms?
What factor influences how an operating system can customize page replacement algorithms?
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Study Notes
Memory Management and Page Faults
- Page faults occur when a thread requires a page that is not currently in physical memory.
- The operating system's first action upon a page fault is to locate a free page frame for the missing page.
- After allocating a free page frame, the system initiates disk I/O to transfer the missing page from virtual memory to the newly identified page frame.
- Upon completion of the I/O operation, the page is loaded into the allocated frame, and the page table for the respective thread is updated to map the virtual page to the physical frame.
- Once the page table is updated, the thread can resume execution from the point of the page fault.
Page Replacement Algorithm
- Operating systems often run page replacement algorithms to manage memory by freeing up page frames.
- This proactive management helps prepare for future page faults by ensuring available frames can be allocated when needed.
- Systems may overcommit physical memory, similar to airlines overbooking seats, operating under the assumption that not all pages will be required simultaneously.
Customization Opportunities
- The operating system lacks insight into the specific memory access patterns of applications, leading to potential inefficiencies in page replacement algorithms.
- Customization of page replacement strategies can be beneficial, particularly for applications with known access patterns, enhancing overall system performance.
- Similar customization options are available for process scheduling and the handling of external events like interrupts in the operating system.
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