# Recent questions tagged tlb 1
Consider a single-level page table system, with the page table stored in the memory. If the hit rate to TLB is $80\%$, and it takes $15$ nanoseconds to search the $TLB$, and $150$ nanoseconds to access the main memory, then what is the effective memory access time, in nanoseconds? $185$ $195$ $205$ $175$
2
A CPU generates $32$-bit virtual addresses. The page size is $4$ KB. The processor has a Translation Look-aside Buffer (TLB) which can hold a total of $128$ page table entries and is $4$-way set associative. The minimum size of the TLB tag is $\text{11 bits}$ $\text{13 bits}$ $\text{15 bits}$ $\text{20 bits}$
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Write a program that can be used to compare the effectiveness of adding a tag field to $TLB$ entries when control is toggled between two programs. The tag field is used to effectively label each entry with the process id. Note that a nontagged $TLB$ can be ... your simulation behaves as expected for a simple (but nontrivial) input example. Plot the number of $TLB$ updates per $1000$ references.
4
Write a program that demonstrates the effect of $TLB$ misses on the effective memory access time by measuring the per-access time it takes to stride through a large array. Explain the main concepts behind the program, and describe what you expect the output to ... . Repeat part $(b)$ but for an older computer with a different architecture and explain any major differences in the output.
5
How can the associative memory device needed for a $TLB$ be implemented in hardware, and what are the implications of such a design for expandability?
1 vote
6
A computer whose processes have $1024$ pages in their address spaces keeps its page tables in memory. The overhead required for reading a word from the page table is $5\: nsec.$ To reduce this overhead, the computer has a $TLB,$ which holds $32$ (virtual page, physical page frame) pairs, and can do a lookup in $1\: nsec.$ What hit rate is needed to reduce the mean overhead to $2\: nsec?$
1 vote
7
You are given the following data about a virtual memory system: The $TLB$ can hold $1024$ entries and can be accessed in $1$ clock cycle $(1\: nsec).$ A page table entry can be found in $100$ clock cycles or $100\: nsec.$ The average page replacement time is $6\: msec.$ ... by the $TLB\:\: 99\%$ of the time, and only $0.01\%$ lead to a page fault, what is the effective address-translation time?
1 vote
8
Consider the following C program: int X[N]; int step = M; /* M is some predefined constant */ for (int i = 0; i < N; i += step) X[i] = X[i] + 1; If this program is run on a machine with a $4-KB$ page size and $64$-entry $TLB,$ what values ... $TLB$ miss for every execution of the inner loop? Would your answer in part $(a)$ be different if the loop were repeated many times? Explain.
9
If a page is not present in the memory, then its corresponding entry in the page table would have the ‘Present’ bit set as 0 to indicate , the page is not present. Will this entry be considered for caching in TLB? As I understand from above line in Tanenbaum, The entry should not be present in TLB. Is my understanding right?
1 vote
10
Consider a paging system with the page table stored in memory. If a memory reference takes $200$ nanoseconds, how long does a paged memory reference take? If we add a Translation Lookaside Buffer (TLB) and $75$ percent of all page-table references are TLB hits, ... effective memory reference time? Assume that finding a page-table entry in the TLB takes $20$ nanoseconds, if the entry is present.
11
A simplified view of thread states is $Ready$, $Running$, and $Blocked$,where a thread is either ready and waiting to be scheduled, is running on the processor, or is blocked (for example, waiting for I/O). This is illustrated in Figure 9.31. Assuming a thread is ... change? c. Will the thread change state if an address reference is resolved in the page table? If so, to what state will it change?
12
Assume that a program has just referenced an address in virtual memory. Describe a scenario in which each of the following can occur. (If no such scenario can occur, explain why.) • $TLB$ miss with no page fault • $TLB$ miss and page fault • $TLB$ hit and no page fault • $TLB$ hit and page fault
1 vote
13
Given the following information: TLB hit rate 95%, TLB access time is 1 cycle. cache hit rate 90 %, cache access time is 1 cycle. When TLB and cache both get miss; page fault rate is 1% The TLB access and acache access are sequential. ... 75 cycles Access to hard drive requires 50,000 cycles. Compute the average memory access latencies when the cache is physically addresses (in cycles).
14
A demand paging uses a TLB and a single level page table stored in main memory. The memory access time is 5s. The page fault service time is 25s. If 70% of access is in TLB and of the remaining, 20% is not present in the main memory. The effective memory access time is? Thanks!
15
Consider a system where TLB lookup time is $25$ ns and memory access time is $200$ ns, respectively. Assuming a virtual address space of $2$ KB, page size of $32$ bytes, and a PTE size of $2$ bytes, what is the minimum TLB hit ratio that results in an average v2p (virtual to physical) translation latency of $185$ ns?
16
A computer system implements a 38 bit virtual address, page size of 16 KB, and 256 entries translation look aside buffer (TLB) organized into 32 sets each having 8 ways. If TLB tag does not store any process id. The minimum length of TLB tag in bits is____
1 vote
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How they calculated time for number of levels?
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A TLB is a hardware device used for speeding up the conversation from virtual address to physical address. Consider a memory management unit where a memory reference takes 500 nanoseconds; TLB (Translation Look aside Buffer) reference takes 40 nanoseconds; and the hit-rate achieved with the ... no TLB ____ Here I got EMAT using TLB ==> 640ns EMAT wthout TLB ==> 1000ns how to calculate speed Up.?
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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 do ... Solution: 10ns + (1 - p) 50ns = 20ns p =4/5 = .80 The TLB hit rate has to be 80% for a mean access time of 20ns.
20
A computer whose processes have 1024 pages in their address spaces keeps its page tables in memory. The overhead required for reading a word from the page table is 500 nsec. To reduce this overhead, the computer has tlb which holds 32 entries and can do look up in 100 nsec. What hit rate is needed to reduce the mean overhead to 200 nsec? can anyone solve this
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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
1 vote
23
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.
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I am having troble with these following questions. Please I need help
25
I know that every process has its own page table and but is it the same with TLB? Does every process have its own TLB or there is a master TLB which is used by all the processes?