Recent questions and answers in Operating System - GATE CSE Doubts

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applied gate:OS
A system uses 48 bit logical address and page size of 16 KB.Multilevel paging is used . A page table entry is of 4B. The total number of pages that are required to store the inner page table entries of a process in the outermost level of paging is:

asked 19 hours ago in Operating System by abhinav649 (59 points) | 4 views

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applied gate:OS(shared variable)
initial value of s and t is 1

asked 19 hours ago in Operating System by abhinav649 (59 points) | 4 views

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ME CBT2 2020
A COMPUTER SYSTEM IMPLEMENTS A 36 BIT VIRTUAL ADDRESS. PAGE SIZE OF 4 KB AND THE SIZE OF PHYSICAL MEMORY IS 30 BITS. THE APPROXIMATE SIZE OF PAGE TABLE IN THE SYSTEM IS __________ MB. [ASSUME MEMORY IS BYTE ADDRESSABLE].

answered 1 day ago in Operating System by SuvasishDutta (163 points) | 24 views

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Self Doubt: Paging
We know that the paging formula is given by $P(ps+m) + (1-P)(m)$ where $P=Page-fault-rate$ $PS=Page-fault-service-time$ $m=memory-access$ Why there is only $1$ memory access when there is no page fault? Shouldn’t there be $2$ memory access assuming single level page table, $1$ for page table access and the other for accessing the frame of the memory?

asked 1 day ago in Operating System by Debapaul (620 points) | 12 views

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OS : Ace test series

asked 1 day ago in Operating System by Chirag Shilwant (159 points) | 25 views

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Made Easy test series os multi subject synchronization

asked 1 day ago in Operating System by Ram Swaroop (155 points) | 5 views

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operatingSystem deadlock
how no mutual exclusion is there? and also Deadlock one of the necessary condition is Mutual exlcusion.

asked 2 days ago in Operating System by kalra05 (37 points) | 8 views

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Made easy test series : Process scheduling SRTF
Consider the following set of process: Operating system uses preemptive shortest remaining time first algorithm, average waiting time ________ (ms). (Upto 1 decimal places) [Ties are broken with lowest process ID number] Note: (i) Consider only ... . (iii) I/O of the process can be done parallelly. Can someone provide gantt chart for above question?

asked 2 days ago in Operating System by vishal burnwal (119 points) | 13 views

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#ProcessScheduling
Does FIFO cause starvation??

asked 2 days ago in Operating System by nandani17 (29 points) | 10 views

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Ace Test Series Question 7
Anyone please clarify.

answered 3 days ago in Operating System by SuvasishDutta (163 points) | 14 views

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GATE GURU: TIME COMPLEXITY
In this question if we solve using logarithm we get time complexity of $g(n)>f(n)=h(n)$ But is taking $logarithm$ to find out the complexity always a safe way? I believe $NOT$. To support my claim I provide u with this link→ https://cs.stackexchange.com/ ... $logf(n)=O(log$ $g(n))$ So what is the approach to solve this problems to be $100\%$ sure about the ans?

asked 5 days ago in Operating System by Debapaul (620 points) | 18 views

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SELF DOUBT: QUESTION ON TLB
The virtual address generated by a CPU is 32 bits. The Translation Look-aside Buffer (TLB) can hold total 64 page table entries and a 4-way set associative (i.e. with 4- cache lines in the set). The page size is 4 KB. The minimum size of TLB tag is (A) 12 bits (B) 15 bits (C) 16 bits (D) 20 bits

answered 5 days ago in Operating System by vikas999 (55 points) | 20 views

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PAGING SELF DOUBT
Consider a computer system using 2-level paging with TLB.The logical address supported is 32 bits.The page table is divided into 512 pages each of size 1K.The memory access time is 100ns and the TLB access time 15ns .Page table entry size at 1st level is 2 Bytes ... $4B$ so the overhead of the 1st level should be $2^{21}B$ right? So total overhead→ $1KB+2048KB=2049KB$ right?

asked 5 days ago in Operating System by Debapaul (620 points) | 27 views

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self doubt->deadlock
Suppose we have a code like this: i=0 j=0 P1 P2 while(i==0); while(j==0); { { CS CS i=1; j=1; } } And in GATE we are asked if deadlock exists/not then should we state that deadlock doesnot exists(as here we have a livelock not a deadlock)

asked 5 days ago in Operating System by Doraemon (91 points) | 5 views

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SELF DOUBT: SIZE OF INNER PAGE TABLE
In a two level paging environment a page table is divided into $2^{12}$ pages each of size $4 KW$. The memory is word addressable, The physical address space is $128 MW$. Memory is divided into $2^{14}$ frames. The size of inner page table is ... $of$ $pages$ in the each inner page table $* Page size$ But how to find number of pages in the inner page table ?

asked 5 days ago in Operating System by Debapaul (620 points) | 13 views

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SELF DOUBT:OPERATING SYSTEM
Consider a system with a $2$ $level$ paging applicable the page table is divided into $8K$ pages each of size $16KB$. The memory is Byte addressable if the physical address space is $128MB$ which is divided into $4KB$ frames. The PTE size of the ... table entry size of the inner page table is $64bits$. What will be the page table size of the inner and outer page table?

asked 5 days ago in Operating System by Debapaul (620 points) | 16 views

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indexing questions
Consider a file currently consisting of 100 blocks. Assume that the file-control block (and the index block, in the case of indexed allocation) is already in memory. In the contiguous-allocation case, assume that there is no room to grow at ... operations are required for contiguous, linked, and indexed (single-level) allocation strategies, if a block is removed from the middle.

answered 6 days ago in Operating System by shashin (1.2k points) | 34 views

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Forks Theory
Can anyone provide good references(NPTEL etc or some other good ones) for understanding theory about fork()?

asked 6 days ago in Operating System by Shivateja MST (96 points) | 7 views

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translation lookaside buffer
does TLB stores both frame no along with the page no as its entry?

asked 6 days ago in Operating System by Divyaok (20 points) | 19 views

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multilevel paging
Suppose that we have a two-level page translation scheme with 4K-byte pages and 4-byte page table entries (includes a valid bit, a couple permission bits, and a pointer to another page/table entry). What is the format of a 32-bit virtual address? how do we solve such questions.

asked 6 days ago in Operating System by Divyaok (20 points) | 10 views

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pagining concept from os
Assume a system with 2-levels of paging with the main memory access time of 100ns, and the cache lookup time of 50ns. Assuming a cache hit rate of 90% and no parallel memory access , what is the average time to read a location from main ... sugested explanation says 3 memory accesses would be required however i got my answer as 60nsec. can someone please help me with this.

asked 6 days ago in Operating System by Divyaok (20 points) | 38 views

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GATE GURU: OS GATE 20
Assume that a task is divided into four equal-sized segments and that the system builds an $eight-entry$ page descriptor table for each segment. Thus, the system has a combination of segmentation and paging. Assume also that the page size is $2$ ... each segment and the maximum logical address space for the task? What does this question trying to convey and how to approach?

asked Jan 13 in Operating System by Debapaul (620 points) | 9 views

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GATE GURU OS 101
Consider a system with a 6-bit virtual address space and a 16-byte page-frame. The mapping from virtual page numbers to physical frame numbers of a process is (0,8), (1,3), (2,11), and (3,1). Translate 20 (virtual addresses) to physical addresses. Note that all ... The mapping from virtual page numbers to physical frame numbers of a process is (0,8), (1,3), (2,11), and (3,1).

asked Jan 12 in Operating System by Debapaul (620 points) | 13 views

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GATE GURU : OPERATING SYSTEM
Consider a system with memory mapping done on a page basis and using a $single- level$ page table. Assume that the necessary page table is always in memory and memory reference takes $200 ns$. Now we add an MMU that imposes an overhead of $20 ns$ on a hit or ... of all memory references hit in the MMU TLB, what is the Eﬀective Memory Access Time (EMAT)............. $?$

asked Jan 12 in Operating System by Debapaul (620 points) | 14 views

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Self Doubt: Finitely Many and Infinitely many
What is the difference between $finitely$ $many$ and $infinitely$ $many?$ According to me $(x-1)(x-2)=0$ has finitely many solutions as $x$ can be $1$ $or$ $2$ where as $(x+1)^2=(x+1)(x+1)$ has infinitely many solution. So $finitely$ $many$ basically boils down to $number$ $of$ $solutions$ $>1$ but $not$ $infinite$ Is my understanding right?

asked Jan 12 in Operating System by Debapaul (620 points) | 11 views

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Made Easy : Virtual Memory
On a machine with 32-bit addresses, suppose an OS uses two-level page tables with a ﬁrst level page table has 2048 entries and each second level page table has 2048 entries. What is the size of a page?

asked Jan 12 in Operating System by Debapaul (620 points) | 19 views

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Virtual memory: Self Doubt
Ans is $8.75$ $cycles$ right?

answered Jan 12 in Operating System by shashin (1.2k points) | 17 views

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Self Doubt; Virtual Memory
Assume that in a certain computer, the virtual addresses are 64 bits long and the physical addresses are 48 bits long The above line is an extract from GATE 2019 Question. Now I have this doubt,(don't know why i didn't had it for so long) How can the logical address be longer than the physical address?

answered Jan 12 in Operating System by shashin (1.2k points) | 13 views

+1 vote

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ace test series memory management mock test
Q. 4.

asked Jan 11 in Operating System by Rahul Burman (19 points) | 20 views

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Made Easy test series question #OS
Why can't the answer be round robin?

asked Jan 11 in Operating System by RubyGATE (9 points) | 19 views

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Self Doubt-Deadlock
Why single resource or single instace with many processes cannot form deadlock? Just give an example-----

answered Jan 10 in Operating System by shashin (1.2k points) | 31 views

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Synchronization Problem
Can anyone provide good reference to read Second Readers Writers Solution?

asked Jan 8 in Operating System by Shivateja MST (96 points) | 5 views

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ace test series - demand paging

answered Jan 8 in Operating System by SuvasishDutta (163 points) | 15 views

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ACE TEST SERIES - deadlock

asked Jan 8 in Operating System by Jean (8 points) | 41 views

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Made easy test series : Process scheduling concept

answered Jan 8 in Operating System by yadavg123 (17 points) | 17 views

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made easy test question
which of the following is typically not true about dynamic linking? I) Dynamic linking decreases memory space utilization. II)dynamc linking increases memory space utilization. III)Dynamic linking practically used in majority of operating system. In answer first statement is given correct .i don’t know how?

asked Jan 8 in Operating System by abhinav649 (59 points) | 10 views

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SELF DOUBT: MULTILEVEL FEEDBACK QUEUE
Can someone provide me some important points on $Multilevel$ $ feedback$ $queue?$

asked Jan 7 in Operating System by Debapaul (620 points) | 6 views

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GATEFORUM OS
A virtual memory system uses the demand paging for its implementation. The Probability of getting page faults is $0.25$ and the normal memory access time is $200ns$. If it takes $2ms$ to service a page fault then what is the effective memory access time (in $ns$)? I have solved this ... $=> p(ps)+m$ $=> 0.25(2*10^6)+200$ $=>500200ns$ But they have given the ans Who is right?

answered Jan 7 in Operating System by shashin (1.2k points) | 20 views

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Test Series Question
Consider a system supporting a logical address of 62 bits ,the page size of 4 kB and page table entry size 32 bits.The system uses multilevel paging .How many levels of multipaging is required if the outer page table should fit in exactly 1 frame?

answered Jan 7 in Operating System by priyesh9875 (59 points) | 20 views

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Self Doubt - Object Code, Relocation, Linkers (2-passes) and Loaders

answered Jan 7 in Operating System by yadavg123 (17 points) | 27 views

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