Questions and Answers of Operating Systems Internals And Design Principles

Now revisit the previous question using a hole list. How much memory is needed for the list in the best case and in the worst case? Assume the operating system occupies the bottom 512 KB of memory.
In Sec. 4.8.4, it was pointed out that it would be better to search for holes for the text and data segments separately. Implement this improvement.Data from Sec. 4.8.4 The code for exec follows the
If an instruction takes 1 nsec and a page fault takes an additional n nsec, give a formula for the effective instruction time if page faults occur every k instructions.
A computer with a 32-bit address uses a two-level page table. Virtual addresses are split into a 9-bit top-level page table field, an 11-bit second-level page table field, and an offset. How large
Suppose that a 32-bit virtual address is broken up into four fields, a, b, c, and d. The first three are used for a three-level page table system. The fourth field, d, is the offset. Does the number
The TLB on the VAX did not contain an R bit. Was this omission just an artifact of its era (1980s) or is there some other reason for its absence?
A computer has four page frames. The time of loading, time of last access, and the R and M bits for each page are as shown below (the times are in clock ticks):(a) Which page will NRU replace?(b)
A machine has 48-bit virtual addresses and 32-bit physical addresses. Pages are 8 KB. How many entries are needed for the page table?
A RISC CPU with 64-bit virtual addresses and 8 GB of RAM uses an inverted page table with 8-KB pages. What is the minimum size of the TLB?
A small computer has 8 page frames, each containing a page. The page frames contain virtual pages A, C, G, H, B, L, N, D, and F in that order. Their respective load times were 18, 23, 5, 7, 32, 19,
Are there any circumstances in which clock and second chance choose different pages to replace? If so, what are they?
Suppose that a computer uses the PFF page replacement algorithm but there is sufficient memory to hold all the processes without page faults. What happens?
Given the results of the previous problem, why are pages so small? Name two disadvantages of 64-KB pages with respect to 4-KB pages.Data from previous problemHow long does it take to load a 64-KB
Figure 4-44 shows the initial memory usage of the first four components of a MINIX 3 system. What will be the cs value for the next component loaded after rs? ds text data CS 0000800 0005800 19552
One of the first timesharing machines, the PDP-1, had a memory of 4-KB 18-bit words. It held one process at a time in memory. When the scheduler decided to run another process, the process in memory
When segmentation and paging are both being used, as in the Pentium, first the segment descriptor must be looked up, then the page descriptor. Does the TLB also work this way, with two levels of
IBM-compatible computers have ROM and I/O device memory not available for program use in the range from 640 KB to 1 MB, and after the MINIX 3 boot monitor relocates itself below the 640-KB limit the
Why does the MINIX 3 memory management scheme make it necessary to have a program like chmem?
In the previous problem does it matter whether the boot monitor takes exactly as much memory as it needs or if it is rounded up to units of clicks?Data from previous problemIBM-compatible computers
Fig. 5-4 lists some file attributes. Not listed in this table is parity. Would that be a useful file attribute? If so, how might it be used? Attribute Protection Password Creator Owner Read-only
Redesign adjust to avoid the problem of signaled processes being killed unnecessarily because of a too-strict test for stack space.
To tell the current memory allocation of a MINIX 3 process you can use the command chmem +0 a.out but this has the annoying side effect of rewriting the file, and thus changing its date and time
NTFS uses Unicode for naming files. Unicode supports 16-bit characters. Give an advantage of Unicode file naming over ASCII file naming.
Some files begin with a magic number. Of what use is this?
Consider the directory tree of Fig. 5-7. If /usr/jim/ is the working directory, what is the absolute path name for the file whose relative path name is ../ast/x?
Give 5 different path names for the file /etc/passwd.
Systems that support sequential files always have an operation to rewind files. Do systems that support random access files need this too?
Consider the following proposal. Instead of having a single root for the file system, give each user a personal root. Does that make the system more flexible? Why or why not?
Figure 5-10 shows the structure of the original FAT file system used on MS-DOS. Originally this file system had only 4096 blocks, so a table with 4096 (12-bit) entries was enough. If that scheme were
The UNIX file system has a call chroot that changes the root to a given directory. Does this have any security implications? If so, what are they?
The UNIX system has a call to read a directory entry. Since directories are just files, why is it necessary to have a special call? Can users not just read the raw directories themselves?
A standard PC can hold only four operating systems at once. Is there any way to increase this limit? What consequences would your proposal have?
An operating system only supports a single directory but allows that directory to have arbitrarily many files with arbitrarily long file names. Can something approximating a hierarchical file system
The performance of a file system depends upon the cache hit rate (fraction of blocks found in the cache). If it takes 1 msec to satisfy a request from the cache, but 40 msec to satisfy a request if a
What is the difference between a hard link and a symbolic link? Give an advantage of each one.
Name three pitfalls to watch out for when backing up a file system.
A disk has 4000 cylinders, each with 8 tracks of 512 blocks. A seek takes 1 msec per cylinder moved. If no attempt is made to put the blocks of a file close to each other, two blocks that are
Would compacting disk storage periodically be of any conceivable value? Explain.
What is the difference between a virus and a worm? How do they each reproduce?
Three different protection mechanisms that we have discussed are capabilities, access control lists, and the UNIX rwx bits. For each of the following protection problems, tell which of these
Can the Trojan horse attack work in a system protected by capabilities?
The size of the filp table is currently defined as a constant, NR_FILPS, in fs/const.h. In order to accommodate more users on a networked system you want to increase NR_PROCS in
Suppose that a technological breakthrough occurs, and that nonvolatile RAM, which retains its contents reliably following a power failure, becomes available with no price or performance disadvantage
Symbolic links are files that point to other files or directories indirectly. Unlike ordinary links such as those currently implemented in MINIX 3, a symbolic link has its own i-node, which points to
Although the current limit to a MINIX 3 file size is determined by the 32-file pointer, in the future, with 64-bit file pointers, files larger than 232 − 1 bytes may be allowed, in which case
Show if setting the (now-unused) ROBUST flag might make the file system more or less robust in the face of a crash. Whether this is the case in the current version of MINIX 3 has not been researched,
Design a mechanism to add support for a ‘‘foreign’’ file system, so that one could, for instance, mount an MS-DOS file system on a directory in the MINIX 3 file system.
Write a pair of programs, in C or as shell scripts, to send and receive a message by a covert channel on a MINIX 3 system. A permission bit can be seen even when a file is otherwise inaccessible, and
Implement immediate files in MINIX 3, that is small files actually stored in the i-node itself, thus saving a disk access to retrieve them.
How can the hold-and-wait condition be prevented?
Explain thrashing.
What is usually the critical performance requirement in an interactive operating system?
What is the difference between turnaround time and response time?
What characteristics distinguish the various elements of a memory hierarchy?
What is cache memory?
What is multiprogramming?
Explain the distinction between a real address and a virtual address.
Describe the round-robin scheduling technique.
What is multithreading?
Define jacketing.
What is a monitor?
For process scheduling, does a low-priority value represent a low priority or a high priority?
Briefly define round-robin scheduling.
Briefly define shortest-process-next scheduling.
Briefly define shortest-remaining-time scheduling.
Briefly define highest-response-ratio-next scheduling.
Generalize the result of Problem 11.1 to the case in which a program refers to n devices.Data in Problem 11.1Consider a program that accesses a single I/O device and compare unbuffered I/O to the use
What is a file management system?
What criteria are important in choosing a file organization?
What are the advantages of using directories?
What is an embedded OS?
Briefly describe container virtualization.
Explain the concept of ballooning.
What is OpenStack?
Define the Internet of Things.
What is RIOT?
What is the major function of the network access layer?
What tasks are performed by the transport layer?
What is a protocol?
What is a protocol architecture?
What is TCP/IP?
What is the purpose of the Sockets interface?
In to retransmit lost packets, TFTP must keep a copy of the data it sends. How many packets of data must TFTP keep at a time to implement this retransmission mechanism?
TFTP, like most protocols, will never send an error packet in response to an error packet it receives. Why?
TFTP’s time-out-and-retransmission scheme implies that all data packets will eventually be received by the destination host. Will these data also be received uncorrupted? Why or why not?
This chapter mentions the use of Frame Relay as a specific protocol or system used to connect to a wide area network. Each organization will have a certain collection of services available (like
What is middleware?
Because we have standards such as TCP/IP, why is middleware needed?
Discuss some of the reasons for implementing process migration.
How is the process address space handled during process migration?
What are the motivations for preemptive and nonpreemptive process migration?
Why is it impossible to determine a true global state?
Define the two types of distributed deadlock.
At an ATM machine in a supermarket, the average length of a transaction is two minutes, and on average, customers arrive to use the machine once every five minutes. How long is the average time that
What factors determine the time quantum in round robin scheduling? Consider the system:Context switch takes a time of 1 unit. Compute the average turnaround time of the processes for the time quanta
Consider a memory-management system that uses simple paging strategy and employs registers to speed up page lookups. The associative registers have a lookup performance of 120 ns and a hit ratio of
What is relocation of a program?
What requirements is memory management intended to satisfy?
What are the advantages of organizing programs and data into modules?
What is address binding? State the different timings when address binding may occur.

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