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Operating Systems 3rd edition Gary Nutt - Solutions
In a hypothetical Linux system, each virtual address is 32 bits with a 10-bit page size, 256-entry page table, 32l-entray page middle directory, and 256-entry page directory. Using the Linux model described in this chapter, what is the page directory entry, page middle directory entry, page table
Contemporary computers often have more than 100MB of physical memory. Suppose the page size is 2KB. How many entries would an associative memory need in order to implement a page table for the memory?
Use an example to explain the different representations of a reference to a variable in the name space, the virtual address space, and the physical address space. Using your example, show how the virtual address is derived from the name and how the physical address is derived from the virtual
What factors could influence the size of the virtual address space in a modern computer system? In your answer, consider the memory-mapping unit, complier technology, and instruction format.
What factors could influence the size of the physical address space in a modern computer system? (Consider various parts of the hardware.)
A researcher a Famous University invented a new static demand paging algorithm, called the future least frequently used (or FLFU) strategy in which the page chosen for replacement is the one that is currently loaded, but which will be the least frequently used in the future (the researcher did not
Professor Jabberwocky of More Famous University read about the FLFU algorithm from the previous problem, and published a paper with a proof that FLFU is optimal. Argue for or against Jabberwocky’s conjecture.
Suppose R = 3, 2, 4, 3, 4, 2, 2, 3, 4, 5, 6, 7, 7, 6, 5, 4, 5, 6, 7, 2, 1 is a page reference stream.a. Given a page frame allocation of 3 and assuming the primary memory is initially unloaded, how many page faults will the given reference stream incur under Belady’s optimal algorithm?b. Given a
Let R = 0, 3, 1, 4, 1, 5, 1, 6, 0, 5, 2, 6, 7, 5, 0, 0, 0, 6, 6, 6, 6 be a page reference stream. Answer part a-e for problem 11 for this reference stream.
Describe a program that could be expected to have the following:a. A small code locality and a small data localityb. A small code locality and a large data localityc. A large code locality and a small data localityd. A large code locality and a large data locality
Suppose hardware was designed to incorporate three reference bits rather than the single bit used in the LRU implementation described in Section 12.3. Explain how a better approximation to LRU could be achieved using the 3-bit field than can be achieved using the single reference bit.
What is the advantage of the page fault frequency algorithm over the estimation of the working set using the window size w? What is its disadvantage?
In a paging system, page boundaries are transparent to the programmer. Explain how a loop might cause thrashing in a static allocation paging system when the memory allocation is too small.
Why is locality not an issue in a segmentation system?
Explain how it might be possible to build an OS that uses full segmentation, but has no file system.
Suppose two processes share a main program segment, but each has its own private implementation of a procedure called from the main segment and private data segments. Draw a figure similar to Figure to illustrate how the segment registers and segments might be set up to accommodate this situation.
Write a program to determine how a UNIX kernel write () operation treats bytes that are interior to a byte stream. Does the write () operation insert a block of characters, overwrite a block of characters, or use some other strategy?
Write a program to determine how a Windows kernel writeFile () operation treats bytes that are interior to a byte stream. Does the writeFile () operation insert a block of characters, over-write a block of characters, or use some other strategy?
Explain what the O_APPEND flag is used for in UNIX file I/O
Explain what the O_FILE_APPEND_DATA flag is used for as a value for the dwFile ACCESS argument in Windows file I/O.
Provide an example application or application domain in which sequentially accessed files are well suited to the problem. Your domain should illustrate that in some cases the information must be randomly accessed, yet at other times it must be sequentially accessed.
Suppose a disk free space list indicates that the following blocks of storage are available: 13 blocks, 11 blocks, 18 blocks, 9 block, and 20 blocks. There is a request allocate 10 contiguous blocks to a file.a. Using the first-fit allocation strategy, which block would be allocated to the file?b.
How many device operations (for example, disk sector read () and write () operations) are required to add a released node to free list, where the free list is implemented with the linked-list approach? Do two-way linked lists decrease the number of device operations?
How many device operations are required to add a released node to a free list when the block status map approach is used to implement the free list?
Explain why a file system that supports indexed sequential files cannot be expected to have the same performance level as pure sequentially accessed files.
Suppose a file system is based on the index allocation strategy for managing blocks. Assume each file has a directory entry giving the filename, first index block, and the length of the file. The first index block points, in turn, to 249 file block and to the next index block. If the file is
Suppose a UNIX disk block will hold 2048 disk addresses. What is the maximum-sized file using only the direct pointers?Single-indirection capability?Double-indirection capability?Triple-indirection capability?
Early versions of the DOS file system had a limitation of 32MB of addressable space on a disk drive. Based on the description of the directory and files in the chapter, provide some conjectures for the limitation.
Suppose a file system is organized like the DOS file system and the device index contains 64K pointers. Explain how the file manager could be designed to use the 64K pointers to reference every 512-bytes block on a 512Mb disk.
File system checkers often take advantage of the block status map used to identify unallocated disk blocks. The basic idea is for the map to be copied into the checker’s address space, with each entry in the map enlarged to capture more possibilities for the block’s state (for example,
Use a text editor to inspect a mail file on the computer on which you keep your electronic mail. Assuming it is similar to the Berkeley mail system, you should be able to recognize message boundaries as well as the massage sender, receiver, subject line, and so on. Write an access method to read
Characterize each of the following tasks as an authentication task, authorization task, cryptography task, or none.a. Entering your PIN number at an automatic teller machine.b. Allowing James Bond to enter the enemy’s war roomc. Creating a message digest.d. Cashing a check at the credit union.
Here is a bogus “About me” description. Which of the following passwords could be guessed from the About Me?a. Walkerb. jebBrotherc. IBeat Ald. 1600Penn-Ave.NWe. texas
Explain the value of using one-time passwords.
What is a one-way function?
How is a Java applet prevented from copying information from the client machine environment, then returning it to the server?
Assume that a timesharing computer provides a mechanism by which a file can be read by any user, but can be written by only one. Informally describe a security policy for administering student transcripts on the computer system (limit your description to a half of one typed page). Students should
Describe a mechanism–hardware and software–for authenticating users based on their fingerprints. This is an open-ended question in which you are to think about innovative designs based on your imagination (perhaps as it is influenced by movies, science fiction, and so on). Very high-security
Dynamic relocation hardware is usually considered to be a basic memory protection mechanism. What is the protection state in relocation hardware? How does the operating system ensure that the protection state is not changed indiscriminately?
Explain the exact steps a client and server take in Kerberos to authenticate that a message is from the party it claims to be. (You may find it useful to consult the information on the Web regarding Kerberos.)
Given the access matrix in Figure and access control list for each object.
Given the protection state shown in Figure and the rules shown in Figure, do the following. a. Explain how S3 can cause the protection state to be changed so that it has write access to F2. b. Specify two different ways by which S3 can obtain read permission to F1. c. Explain whether S3 can obtain
Use a text editor to read a UNIX system’s password file, /etc/passwd. You should be able to find a single-line entry in the ASCII file for your own login. Speculate how your password is saved in /etc/passwd. What user is the owner of /etc/passwd? Do you have write permission for /etc/passwd?
Consider a variant of the k-bit key and lock scheme described for memory protection whereby a process can access memory blocks for which every bit position set to 1 within the lock is also set to 1 in the process’s key.a. How many unique locks are in the system?b. Characterize all keys that
Suppose a UNIX a system has been set up so that each student and the instructor have their own ID and all are in the same group (with no other users). The files used by the course are on a timesharing system used by other courses.a. What permissions should a student have on a file that contains a
Explain how the UNIX file protection mechanism could be used to allow any process to read and modify a system file by using special commands named gerSpecial and putSpecial.
Argue for conditions under which the access control method id superior to the capability list approach for implementing the access matrix.
Suppose a 10 Mbps network transmits 1024-byte packets containing a 128-byte header and a 4-byte checksum. If a workstation on the LAN is guaranteed to be able to transmit at least one packet every X time units (since the network is shared with other workstations), what maximum amount of time, as a
A 10 Mbps Ethernet has a minimum gap between packets of 12 bytes, a 22-byte header, and a 4-byte trailer. Assume a user data field of 1464 bytes in a frame, with a minimum gap between each frame.a. What is the maximum theoretical rate at which user data can be transmitted on the Ethernet?b. IP
Rewrite the stop-and-wait algorithm shown in Figure using Windows synchronization primitives. You can use pseudo code for your solution, but use Windows function names for the synchronization calls.Stop and wait algorithm:Sender transmit a frame;Sender sets a time-out on the transmission;Sender
Write a pseudocode description that generalizes the stop-and-wait algorithm in Figure below so that it implements the sliding-window protocol.
Many implementations put the checksum in the trailer, but all the other information describing the frame in the header. Why do network designers do this (instead of just putting the checksum as another field in the header so they could dispense with the trailer)?
Given an IP address of (19910, 12610):a. What is Class A address in dotted decimal notation?b. What is class C address in dotted decimal notation?
What is the Class of each of the following addresses? Convert each Class C address into an IP address of the form (net#, host#):a. 68.38.129.63b. 217,167.115.12.c. 130.34.153.91.d. 63.148.99.227.e. 80.109.69.127.f. 164.145.224.190.
Suppose an internet has the organization shown in Figure, with software using the given transport layer addresses and machines using the given data link layer addresses. a. List the network layer address for each machine. b. Describe the frames used to send a UDP packet from to .
Consider the scheme for employing only partially complete routing tables in each node and gateway of the ARPAnet. If the union of all the information in the partial routing tables is complete, consistent, and stable, explain why routing will operate correctly. There are many details in the actual
The Berkeley UNIX connect system call has a time-out interval of about 1 minute, but the accept call has no time-out interval. Explain why these functions might have been designed in this manner.
Write a pseudo C code definition of the wait For Request function referenced in Figure.
Which of the following commands are idempotent? Explain your answer.a. A command to close a file.b. A command to retract the disk heads from the recording surface.c. A command to step the disk heads up or down one track.d. A command to remove a directory.e. A command to traverse a directory tree.
Suppose a remote disk server system is configured so that the disk on a server has an average block transfer time of 8 milliseconds, while a local disk for a client has an average block transfer time of 88 milliseconds (this would be a very slow disk by today’s standards).a. How fast must the
Contemporary hard disks have rotational speeds ranging from about 4,000 rpm to about 15,000 rpm. Would you expect the access time (the time to move the head over a target block and to transfer it to the disk controller buffer) for the fast disk to be almost 4 times that of the slow disk? Explain
In 1980, empirical studies indicated that the sever was the bottleneck in a remote file system. Assume a stateless file server such as Sun NFS using a packet-level protocol such as raw IP. Hypothesize where bottlenecks would be for file read and write operations.
Given a file server in which the state is distributed between the client and the server, explain why the client and the server must both have copies of file locks for open files.
What are some arguments in favor of and against allowing the same directory to be remotely mounted from two different mount points on two different machines?
What is the advantage of having a file caching server allow only one client to have a file open for writing at any time?
Argue for or against caching files in /bin (on a UNIX system) when they are referenced by a client.
Describe an application domain in which immutable files might be the most effective way to handle file caching between clients and servers.
In the VFS-like file manager design, each file system is mounted and dependent parts of the file manager must do at mount time.
In the VFS-like file manager design, identify and explain three tasks that the independent and dependent parts of the file manager must do at the time a file is opened.
In a certain program, the N elements of the A array are computed in parallel using the same program by the code fragmentfor(i=1; i<=N; i++) {A[i] = A[i21] * B[i];;}Either recommend a data partitioning scheme to achieve good speedup for the computation or argue why it cannot be done.
Suppose that a big, sequential program requires 1,688 seconds to execute on a uniprocessor. A team of programmers partitions the computation into 15 separate computations (called C0, C1, ?, C14). In this partition, C0 has to run by itself to initialize the computation. C13 is error handling code.
Network bandwidths have increased from about 10 Mbps to 1 Gbps in the last decade. However, the latency (time for a message to be transferred from one place to another) has not increased at this rate due to signal propagation bounds. What effect has this change in bandwidth had on remote procedure
Given the comments about network bandwidth and latency in the problem 4 of distributed computing (Ch: 17) (Gary Nutt), what effect has this change in bandwidth had on distributed shared memory technology?
Argue for or against using RPC to implement distributed shared memory.
Could a remote page server for a distributed virtual-memory system be designed to be faster than a conventional remote file server? Argue why or why not.
Compare and contrast the CORBA and Java remote object models. You might consider code mobility, method interface generality, and binding techniques in your answer.
Chaotic relaxation is a variant of SOR where the n worker processes do not bother to synchronize with one another after computing their new estimate of x[i]. How would the code shown in Section 18.2 change to implement chaotic relaxation?
Based on the description in the chapter, what are the differences between Sun RPC and DCE RPC?
How does the notion of a token simplify file consistency in the DCE distributed file system?
What is the purpose of a web proxy?
Mach, CHORUS, and other operating systems use capabilities extensively. Explain how capabilities enable these systems to implement location transparency of entities in a distributed system. How do the capabilities used in CHORUS differ from the capabilities discussed in Chapter 14?
Can a Mach thread read a message it wrote to a task’s port? Why or why not?
Regarding schedulable units of computation:a. Distinguish between a task and a thread in Mach.b. Distinguish between an actor and a thread in CHORUS.c. Distinguish between a process with two threads and two processes that each have one thread.
What is the distinction between a port set in Mach and a port group in CHORUS?
Both Mach and Chorus are implemented as groups of threads in the microkernel, yet they implement a UNIX system call interface. Speculate about how a procedure call interface can be implemented in the UNIX server, yet be implemented with threads.
What prevents the entire page replacement algorithm from being implemented in user space in Mach and CHORUS?
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