Figure 1 shows an approach for memory management. (a) Does the approach (shown in Figure 1) cause any external fragmentation? justify with one sentence (b) list the names of four replacement algorithms. Virtual address Seg # Page # Offset Program Seg table ptr Seg # Segment table Segmentation mechanism Frame # Offset Page # Page table Paging mechanism Offset Page frame Main memory

Figure 1 shows an approach for memory management. (a) Does the approach (shown in Figure 1) cause any external fragmentation? justify with one sentence (b) list the names of four replacement algorithms. Virtual address Seg # Page # Offset Program Seg table ptr Seg # Segment table Segmentation mechanism Frame # Offset Page # Page table Paging mechanism Offset Page frame Main memory

Systems Architecture

7th Edition

ISBN:9781305080195

Author:Stephen D. Burd

Publisher:Stephen D. Burd

Chapter11: Operating Systems

Section: Chapter Questions

Problem 21VE

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4. Figure 1 shows an approach for memory management. (a) Does the approach (shown in (b) list Figure 1) cause any external fragmentation? justify with one sentence the names of four replacement algorithms. Virtual address Seg # Page # Offset Program Seg table ptr Seg # Segment table I Frame # Offset Page # Page table Offset Segmentation mechanism Figure 1. An approach for memory management. Paging mechanism Page frame Main memory
Assume a hypothetical system where disk space has been divided into disk blocks of 25 bytes. The operating system needs to allocate space for a 120-byte file called output_log. Create a diagram for each of the three allocation methods showing how the space might be allocated and what information would be stored in the file directory for that file. For Linked Allocation, assume the first 5 bytes of each block is used for the pointer
What is the difference between internal and external fragmentation? In which memory management techniques internal and external fragmentation can happen? What is the solution for external fragmentation?
What is the working set page replacement algorithm? How does the working set algorithm work? Explain locality of reference with respect to memory references and how this applies to the working set page replacement algorithm.
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A clear and concise description of dynamic memory allocation is presented here for your perusal.
What does the term "memory leak" signify in the context of dynamic memory allocation?
A page table may contain named entries (memory mapped files, such as code of an executable program) and anonymous mappings (page not backed by a file, such as the heap and stack of a program). Explain why (and how) a page fault handler has to handle these two cases differently when it needs to (1) evict a page from physical memory and (2) load a page into physical memory.
In the S/370 architecture, a storage key is a control field associated with each page- sized frame of real memory. Two bits of that key that are relevant for page replace- ment are the reference bit and the change bit. The reference bit is set to 1 when any address within the frame is accessed for read or write, and is set to 0 when a new page is loaded into the frame. The change bit is set to 1 when a write operation is per- formed on any location within the frame. Suggest an approach for determining which page frames are least-recently-used, making use of only the reference bit.
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What is the significance of memory fragmentation, and how can it be managed in memory allocation algorithms?
Main memory size is 16 pages. Size of swap file on hard disk is 64 pages. Operating system locks down pages 0, 1, 2 and 7 in the main memory. Two programs are started and both are provided with a virtual address space of 10 pages. Initially operating system allocates 5 pages of main memory for each program and the rest from swap file. Virtual address space of each program starts from page 0. Construct page tables for both programs at program startup. A page table consists of P-bit which tells if the page is present in the main memory (1 = page is in main memory) and address of the page. Address tells either real address in main memory or the address of the page in swap file. b. A computer with a paged virtual memory system executes two load instructions that are adjacent to each other in memory. Describe the worst case scenario (in terms of performance) that can occur during the execution of the two instructions and explain under which conditions this case occurs. How does this affect…