Quiz 8-12

When the enhanced second chance algorithm, is used, identify the ordered pair that represents a page that would be the best choice for replacement?

(0,0)

A system has a demand-paged memory such that the page table is held in the CPU registers. It requires 8 millisecs to service a page fault when an empty page is available or the replaced page is not modified, and 20 millisecs when the replaced page is modified. Memory access time is 100 nanosecs.It has been observed that the page to be replaced is modified 70 percent of the time. What is the maximum page-fault rate for an effective access time of no more than 200 nanosecs?

(1 - p) * 100 + .7 * p * (2 * 10^7) + .3 * p * .8* 10^7 = 200 100 - 100 * p + (1.4 * 10^7 + .24 * 10^7) * p = 200 (1.64 * 10^7) * p - 100 * p = 100 (1.63999 * 10^7) * p = 100 p = .000006

A Docker -blank1- can execute a Docker -blank2- which creates a Docker -blank3-.

-blank1- Container -blank2- File -blank3- Image

A disk with free blocks 1,5,9,15 would be represented with what bit map?

0100010001000001

In a system that uses partitioning address space, a process has 0x040002 (in hex) in the base register. The limit register has 0x003264. What is the largest legal address for the process?

0x043265

A system has a page size of 256 bytes. For the logical address 0xF9AE (in hexadecimal), what is the page number?

0xF9

Consider a logical address with a page size of 4 KB. How many bits must be used to represent the page offset in the logical address?

12

How many disk accesses are necessary for direct access to byte 19680 using linked allocation and assuming each disk block is 4 KB in size?

19.680 / 4 = 4.92 ≈ 5

Assume the value of the base and limit registers are 150 and 350 respectively. Which of the following addresses is legal?

355

A process uses 41 MB of main Memory. It needs to be swapped and saved to the disk for a while. Assuming a transfer rate of 34 MB/sec, how long will it take in seconds to swap it out to the disk.

41 / 34 = 1.2

The heavier use of a single parity disk is avoided in RAID level ____.

5

Here is a question, followed by a possible answers. Identify the validity of the answers. Question: A file system has the logical as well as the physical block sizes of 512 bytes, and the size of a pointer is 1 byte. The information about each file is already in memory. For the three allocation strategies contiguous, linked, and indexed, answer the questions below: i. How is the logical-to-physical address mapping accomplished in this system? (For the indexed allocation, assume that a file is always less than 512 blocks long.) ii. If we are currently at logical block 10 (the last block accessed was block 10) and want to access logical block 4 (first logical block is block 0), how many physical blocks must be read from the disk? Answer: Let Z be the starting file address (block number). A. Contiguous. Divide the logical address by 512 with X and Y the resulting quotient and remainder respectively. i. Add X to Z to obtain the physical block number. Y is the displacement into that block. ii. 1 B. Linked. Divide the logical physical address by 511 with X and Y the resulting quotient and remainder respectively. i. Traverse the linked list (getting X + 1 blocks). Y + 1 is the displacement into the last physical block. ii. 5 C. indexed. Divide the logical address by 512 with X and Y the resulting quotient and remainder respectively. i. Get the index block into memory. Physical block address is contained in the index block at location X. Y is the displacement into the desired physical block. ii. 3

A i,ii, B i,ii, C i: all true; C ii false

Identify the name of the scheme that permits both the parent and child processes to initially share the same pages, but when one of the processes writes into a page, a copy of the shared page is created.

Copy-on-write

The term used for when a page is brought in the memory only when needed.

Demand paging

A subsystem of three disks {D1,D2,D3} with the same capacity are set-up in RAID 0. To increase the reliability, a subsystem of disks {D4,D5,D6} is added, and this subsystem set up to mirror the other subsystem. What will be the total amount of unique data it can hold in TB, if each disk has a capacity of 3 TB?

Disk = .5 * 3 = 1.5 # of disks = 6 Total amount of unique data = 6 * 1.5 = 9

As opposed to a container, a VM can be deployed in a much shorter time.

False

Does a relative path name begin with "/? ?

False

In Hadoop, the JobTracker created three copies of the same task which are handled by the CopyTrackers.

False

In Live Migration, the dirty pages are tranferred first.

False

One must use Docker technology to implement containers.

False

Rules for preventing the hold-and-wait conditions typically also prevent starvation.

False

The Inverted page table approach requires each process to have its own page table

False

Type 1 hypervisors are special purpose operating systems that run natively on the system hardware. Type 2 hypervisors run as ordinary processes on the host operating system to provide virtualization. Thus, type 2 hypervisors tend to have a higher overall performance than type 1.

False

Very large data centers are more cost effective compared with smaller data centers. Thus all major organizations have one huge single data center rather than having several data centers.

False

When the page-fault rate is too high, the process is likely to have too many frames.

False

Virtual memory in a system permits a higher degree of multiprogramming.

I agree.

Which of the following is not an advantage of permitting a program that is only partially in memory to execute?

It automatically expands the reach of the TLB.

We have executed ln -s /dirA/filenmame1 /dirB/filename3 After that we delete file filename1. What happens to filenmame3?

It includes an invalid pointer.

The free-space list can be implemented using a bit vector approach. Which of the following is a drawback of this technique?

It is not feasible to keep the entire list in main memory for large disks.

Consider a system with 3 fames with this page reference string: 5,6,1,2,6,3,6,4,2,3,6,3,2,1,2,6,1,5,6,1 Try these page replacement algorithms: Optimal, LRU. Find the number of page faults

LRU 5,6,1,2,6,3,6,4,2,3,6,3,2,1,2,6,1,5,6,1 5,5,5,2, ,2, ,4,4,4,6, , ,1, ,1, , ,1, , , 6,6,6, ,6, ,6,6,3,3, , ,3, ,6, ,6, , , 1,1, ,3, ,3,2,2,2, , , ,2, ,2, ,5, , , F,F,F,F,H,F,H,F,F,F,F,H,H,F,H,F,H,H,F,H,H Optimal 5,6,1,2,6,3,6,4,2,3,6,3,2,1,2,6,1,5,6,1 5,5,5,2, ,2, ,2, , ,2, , ,2, , , ,5, , , 6,6,6, ,6, ,4, , ,6, , ,6, , , ,6, , , 1,1, ,3, ,3, , ,3, , ,1, , , ,1, , , F,F,F,F,H,F,H,F,H,H,F,H,H,F,H,H,H,F,H,H page faults: Optimal = 9, LRU = 12

What is the best way of preparing for the final exam in this class?

Listen to all the lectures carefully.

A 32-bit logical address with 14 bit page offset in a single level page table will have a page table with these many entries.

Logical address = 32-bit Page offset = 14-bit # of bits in a page = 32 - 14 = 18 # of pages = 2^18 = 262,144

Do modern operating systems use partitioning of the logical address space for allocating main memory to processes?

No

A system has 4 processes and 3 resource types. Initially there are { 0,0,1 } resources free with allocation and requests as given in the table below. Is the system deadlocked? Allocation Request R1 R2 R3 R1 R2 R3 P1 1 1 1 3 2 1 P2 2 1 2 2 2 1 P3 1 1 0 0 0 1 P4 1 1 1 1 1 1

Not deadlocked

_________ occurs when a virtual machine is configured with more virtual CPUs than there are physical CPUs.

Overcommitment

The formula for the optimal page size we derived by considering the trade-off between

Page table size and Internal Fragmentation

The term for is the number of entries in the Translation Lookaside Buffer multiplied by the page size is:

TLB reach

All files in a single-level directory must have unique names.

True

All major general-purpose CPUs now provide extended amounts of hardware support for virtualization.

True

Consider a system where the optimal page size to ensure a good trade-off between fragmentation and page table entries using the formula is 999 bytes: here, s is the average size of process and e is the size of an entry in the page table. However, a decision was made to go with a page-size of 1024 bytes. Is this a good design choice?

True

Deadlock avoidance and deadlock prevention are different approaches for handling deadlock.

True

In HDFS a name node receives periodic heartbeat from the data nodes. If the heart beat is not detected for a data node, it is replaced by a replacement data node.

True

In HDFS, the JobTracker assignes parts of the data processing tasks to the Tasktrackers on the Slave nodes which run in parallel locally and send partial results to the JobTracker.

True

Microservice Architecture is an architectural style that structures an application as a collection of small autonomous services.

True

One can encapsulate a microservice in a container image along with its dependencies, which then can be used to have on-demand instances of the microservice.

True

The ARM processor uses both single-level and two-level paging

True

The terms "raw" when used to describe a partition, implies that the partition does not have a file system?

True

The wait-for graph approach is not applicable to a resource allocation system with multiple instances of each resource type.

True

When there are multiple instances of each resource type, the banker's algorithm can be used.

True

A general-purpose operating system that also incorporates a virtual machine manager functionality is classified as a

Type 1 hypervisor

Microsoft Windows Server with HyperV is a

Type 1 hypervisor

Linux 2.6.20 or newer includes KVM. Linux with KVM is a

Type 1 hypervisors with an OS

Oracle VirtualBox is a

Type 2 hypervisor

_____ contains information such as the number of blocks in a partition, size of the blocks, and free-block and FCB count and pointers.

Volume Control Block

Which one of these is not a benefit of virtualization.

Where available, live migration of guest between systems decreases downtime, eases administration, allows better resource management

Identify true or false. X. With Local replacement policy each process select from only its own set of allocated frames for replacement. Y. Global replacement permits a process to find a replacement frame from the set of all frames, but not if that frame is currently allocated to some other process.

X is true, Y is false

The Translation Lookaside Buffer needs to be flushed when a context switch occurs (unless an address space identifier is used).

Yes

How are the transfers between the disk and the memory handled?

block at a time

A volume control block ____.

contains information such as the number of blocks in a partition, size of the blocks, and free-block and FCB count and pointers

A file system that uses inodes to represent files. Disk blocks are 8-KB in size and a pointer to a disk block requires 4 bytes. This file system has 12 direct disk blocks,plus single, double, and triple indirect disk blocks. What is the maximum size of a file that can be stored in this file system? (Hint: indirect blocks are also 8-KB allowing 2K pointers).

disk blocks = 8 * 1024 = 8192 B direct block size = 8192 / 4 = 2048 indirect block size = 8192 / 2 = 4096 direct disk block size = 12 * 8192 = 98304 single disk block size = 4096 * 8192 = 33554432 double disk block size = 4096 * 4096 * 8192 = 1.37439 * 10 ^ 11 triple disk block size = 4096 * 4096 * 4096 * 8192 = 5.6295 * 10 ^ 14 maximum file size = 563 terabytes 64 terabytes

A demand-paging system with a disk has an average access and transfer time of 30 milliseconds. Addresses are mapped using a page table in main memory, with an access time of 1microsecond per memory access. Thus, each memory reference through the page table takes two accesses. To improve this time, the designers have added an associative memory that reduces access time to one memory reference,if the page-table entry is in the associative memory.Assume that 80 percent of the accesses are in the associative memory and that, of those remaining, 10 percent (or 2 percent of the total) cause page faults. What is the effective memory access time?

effective access time = 1 + (.1 * 1) + (.02 * 3 * 10^4) = .6 ms

In a system a library routine is named xyz.so. What kind of routine is it?

in the Linux dynamic library

In a virtual machine environment, each VM believes that it has ____

its own memory

MS-DOS uses FAT. How can it be described?

linked allocation

The address generated by the processor is referred to as a ____.

logical address

A system has n processes and m resources types. The Banker's algorithm needs a data structure termed "need" which is a

matrix of size nxm

With a 1024-byte page size, what are the page numbers and offsets for the following address references : a. 42095 (decimal) b. 215201 (decimal)

page size = 2^10 # of bits in offset = 10 page = 41; offset = 111, page = 210; offset = 161 r = 42095 % 2 = 1, val = 21047 r = 21047 % 2 = 1, val = 10523 r = 10523 % 2 = 1, val = 5261 r = 5261 % 2 = 1, val = 2630 r = 2630 % 2 = 0, val = 1315 r = 1315 % 2 = 1, val = 657 r = 657 % 2 = 1, val = 328 r = 328 % 2 = 0, val = 164 r = 164 % 2 = 0, val = 82 r = 41 % 2 = 1, val = 20 r = 20 % 2 = 0, val = 10 r = 10 % 2 = 0, val = 5 r = 5 % 2 = 1, val = 2 r = 2 % 2 = 1, val = 1 r = 1 % 2 = 1, val = 0 42095 binary = 1010 0100 0110 1111 page # = 101001 = 41 offset = 00 0110 1111 = 111 215201 binary = 0011 0100 1000 1010 0001 page # = 11010010 = 210 offset = 0010100001 = 161

In RAID 5, if one of the disks is corrupted, the data can be constructed by

reading all the data in the rest of the disks

A file has several attributes. Which of the following is not one of them?

resolution

What is mount point?

the location within the file structure where the file system is to be attached

A bare metal machine involves the translation VPN -> PPN. When there is virtualization, an additional mapping is needed.

to do the PPN ->MPN mapping.

In HDFS, a block of data by default is

triplicated

Here is a 3-part question and possible answers. Are answers valid? Questions: a. If the pointer to the free-space list is corrupted, can the system recreate the free-space list? Explain your answer. b. In file system (similar to the one used by Linux) with indexed allocation, how many disk I/O operations are required to read the contents of a small local file at /x/y/z.pdf? Assume that none of the disk blocks is currently being cached. c. Suggest a scheme to ensure that the free-space pointer can be recovered if the original pointer is corrupted. Answer: a. If the pointer to the free-space list is corrupted, there is no way the system recreate the free-space list. b. Reading the contents of the small local file /x/y/z.pdf involves 4 separate disk operations: (1) Reading in the disk block containing the root directory /, (2) & (3) reading in the disk block containing the directories x and y, and reading in the disk block containing the file z.pdf. c. The free-space list pointer could be replicated on the disk in multiple locations.

valid, b. invalid, c. valid

This approximates a program's locality.

working set