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Recent questions tagged virtual-memory

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121

TLB OS
Why the formula used here is not P(10) + (1-P)(50) = 20 ?; A computer keeps its page tables in memory. The time required to read a word from the page table is 50ns. To reduce this overhead, the computer has a TLB, which holds 32 (virtual page, physical page frame) pairs and can ... : 10ns + (1 - p) 50ns = 20ns p =4/5 = .80 The TLB hit rate has to be 80% for a mean access time of 20ns.

rahuljai asked in Operating System Dec 3, 2018

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3 answers

122

OS-Virtual Memory
A computer system has a page size of 1024 bytes and maintains page table for each process in the main memory.The overhead required for doing a lookup in the page table is $500ns$.To reduce this overhead, the computer has a TLB that caches 32 ... mappings.A TLB lookup requires $100ns$.What TLB hit-rate is required to ensure an average virtual address translation time of $200ns$?

Ayush Upadhyaya asked in Operating System Dec 2, 2018

by Ayush Upadhyaya

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123

SudoGate Test Series - Virtual Memory
A computer system has TLB access time = 30 ns and the main memory access time is 150 ns and if the miss rate is 20 % the calculate the effective memory access time if 3 level of paging is applied. i am getting 270 ns

Gurdeep Saini asked in Operating System Nov 5, 2018

by Gurdeep Saini

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124

self_doubt
A processor uses 36 bit physical address and 32 bit virtual addresses, with a page frame size of 4 Kbytes. Each page table entry is of size 4 bytes. A three level page table is used for virtual to physical address translation, where the virtual ... table entry of the first, second and third level page tables are respectively. modified from : https://gateoverflow.in/490/gate2008-67

Dharmendra Lodhi asked in Operating System Oct 20, 2018

by Dharmendra Lodhi

954 views

1 vote

2 answers

125

AceBook
Consider the machine with 64 MB Physical Memory and a 34 bit Virtual Address Space. If the page size is 4KB, the appropriate sizes of conventional and inverted page table sizes are: a) 4M, 4K b)4K, 4M c)4M, 16K d)16K, 4M. soln: is Option C. but my ans is (7MB, 28KB)

abhishek1995_cse asked in Operating System Oct 16, 2018

by abhishek1995_cse

1.7k views

1 vote

1 answer

126

Na462 asked in Operating System Sep 29, 2018

by Na462

712 views

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0 answers

127

Self doubt
When the process is in memory and executing with PC value = 100 Let virtual memory concept is used when next process is scheduled and main memory doesn't have space so anyone one of the process(pages) should be swapped out to secondary memory. If currently ... then in order to preserve its state does OS stores its PCB also in Secondary storage ?? and restore later to MM ??

jatin khachane 1 asked in Operating System Sep 14, 2018

by jatin khachane 1

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0 answers

128

Galvin #OS Please explain this diagram from VM.
What exactly is happening here? I can't figure out the arrows!

iarnav asked in Operating System Sep 12, 2018

by iarnav

363 views

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0 answers

129

Testbook Test Series: Operating System - Virtual Memory

sudhir singh asked in Operating System Aug 22, 2018

by sudhir singh

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1 answer

130

Galvin, Virtual memory exercise 9.15
A simplified view of thread states is Ready, Running, andBlocked, where a thread is either ready andwaiting to be scheduled, is running on the processor, or is blocked (for example, waiting for I/O). Assuming a thread is in the Running state, ... will change its state from running to waiting. However, I am highly confused over answers to part b, and part c.

Harsh Kumar asked in Operating System Aug 14, 2018

1.7k views

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0 answers

131

Virtual Memory
An operating system supports a paged virtual memory, using a central processor with a cycle time of 1 microsecond. It costs an additional 1 microsecond to access a page other than the current one. Pages have 1000 words, and the paging device is a ... anybody explain.. Also, I am getting highly frustrated over such questions. Please tell me how to solve these questions correctly?

Harsh Kumar asked in Operating System Aug 13, 2018

444 views

1 vote

3 answers

132

Memory Management and Virtual Memory GATE - 2004
Consider a system with a two level paging scheme in which a regular memory access takes 150 ns, and servicing a page fault takes 8 ms. An average instruction takes 100 ns of CPU time, and two memory accesses. The TLB hit ratio is 90% ... instructions. What is the effective average instruction execution time? a) 645 ns b) 1050 ns c) 1215 ns d) 1230 ns

nishant279 asked in Operating System Aug 7, 2018

2.0k views

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0 answers

133

performance cache exercise help
First level data cache: Direct mapping , writeThrough/write allocate , 8kb data and lines of 8 bytes, miss rate= 17% First level instructions cache: Direct mapping,, 4kb data and lines of 8 bytes, miss rate= 2% Second level unified cache: ... accesses to data memory and instructions of the total number of accesses? 5)What is the average memory access time? Thanks !!

mauro5991 asked in CO and Architecture Aug 2, 2018

403 views

1 vote

0 answers

134

Virtual Memory
How we can improve size of virtual memory?

srestha asked in Operating System Aug 1, 2018

576 views

1 vote

2 answers

135

Virtual Memory
A computer uses 30 bit physical address, 38 bit virtual address and uses 2-level paging. The page table base register stores the base address of the first level, Each page table, occupied exact one page. Each entry of first level store base address of second level ... second level table store a page table entry which is of size 32 bits. The size of page in KB in computer is ________.

Na462 asked in Operating System Jul 19, 2018

by Na462

1.2k views

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0 answers

136

Memory References

Na462 asked in Operating System Jul 19, 2018

by Na462

441 views

1 vote

2 answers

137

Virtual Memory
Which of the following is true? A. If the page size increases page fault rate may also increase. B. Multi-level paging optimizes program execution time. C. Dynamic linking increases program execution time.Correct Option D. TLB is a software data structure.

Na462 asked in Operating System Jul 18, 2018

by Na462

1.7k views

0 votes

1 answer

138

Virtual Memory
Virtual memory increases degree of multiprogramming Virtual memory decreases degree of multiprogramming Degree of multiprogrammoing means number of process is in memory. (and I think memory here is primary memory and not secondary memory such as disk or magnetic tape) ... memory must decreses use of main memory. But according to prediction it is wrong. Where Am I getting wrong?

srestha asked in Operating System Jul 12, 2018

1.9k views

0 votes

1 answer

139

Na462 asked in Operating System Jul 12, 2018

by Na462

532 views

0 votes

1 answer

140

Na462 asked in Operating System Jul 12, 2018

by Na462

767 views

1 vote

1 answer

141

Made easy workbook
Assume that a memory with only 4 pages,each of 16 bytes,is initially empty.The CPU generates the following sequence of virtual addresses and uses the LRU page replacement policy. 0,4,8,20,24,36,44,12,68,72,80,84,28,32,88,92 How many page faults does this sequence cause?What are the page number of ... sequence? A)6 and 1,2,3,4 . B)7 and 1,2,4,5 C)8 and 1,2,4,5 . D)9 and 1,2,3,5

Avik Chowdhury asked in Operating System Jul 10, 2018

by Avik Chowdhury

442 views

2 votes

1 answer

142

Made easy workbook
The number of page faults with a given string "S " using LRU algorithm is "N" and considering the reverse of string S^R the number of page faults will be A)N. B)N/2 C)2N. D)3.75N

Avik Chowdhury asked in Operating System Jul 10, 2018

by Avik Chowdhury

1.2k views

2 votes

2 answers

143

Ace Test Series: Operating System - Virtual Memory And Paging

Na462 asked in Operating System Jul 3, 2018

by Na462

522 views

1 vote

1 answer

144

Topic: virtual memory.
Suppose the average page fault service time is 20 milliseconds and memory access time is 200 nanoseconds. Assuming we wish to have less than 10% degradation in memory access when a page fault occurs estimate the value of the fault rate must be less than.

gidoranking asked in Operating System Jul 2, 2018

810 views

0 votes

1 answer

145

Memory mapped files
Please explain the concept of memory mapped files in OS. Is it really in GATE 2019 Syllabus?

Na462 asked in Operating System Jun 22, 2018

by Na462

311 views

1 vote

1 answer

146

Virtual memory
How does the virtual memory separates the logical memory as perceived by users from physical memory? Is it because we can load program with larger address space then physical memory but still we need physical memory to load our pages don't we ? Then what does the above statement actually trying to convey ?

Na462 asked in Operating System Jun 20, 2018

by Na462

1.1k views

1 vote

1 answer

147

Paging
In multi-level paging, a big page table is divided into smaller pages and for those pages (of main page table) a new page table is created. So what be basically did is broke down the main page table into small pieces (usually so to reduce the size of parts to page size). But, the overall size of the main page table remain same, right? Then what actually is the benefit of multilevel paging?

Ankit Sahu asked in Operating System Apr 26, 2018

898 views

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0 answers

148

caching and virtual memory
I am having troble with these following questions. Please I need help

Samson Bankole asked in Operating System Apr 19, 2018

by Samson Bankole

376 views

2 votes

0 answers

149

Operating System By Harris
Assume the amount of memory on a system is inversely proportional to page fault rate. Each time when memory doubles the page fault rate is reduced by third. Currently system has 32mb of memory and page fault rate is 2% the main memory access time is ... is 300 μ sec. if the main memory is increased to 128 mb, then what would be the overall effective access time________.

satendra asked in Operating System Apr 8, 2018

1.8k views

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0 answers

150

Virtual Memory
Say i have a Cache with hit ratio 96% and access time 1ns and a memory with access time 10 ns Now by default we go for Sequential access instead of Parallel Now... Tavg = 0.96*(1) + 0.4*(1+10) this will be the answer rt? My doubt is For ... one to apply?? Like used in Question:- https://gateoverflow.in/788/gate2003-78 they have used First one instead of Second.Please help me out??

Na462 asked in CO and Architecture Apr 4, 2018

by Na462

182 views

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Recent questions tagged virtual-memory