OS Test 2
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
Help!
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| show | results when several threads try to access and modify the same data concurrently
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| show | Peterson's solution
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| show | atomicity
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| _______ refers to where a process is accessing/updating shared data. | show 🗑
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| _____ can be used to prevent busy waiting when implementing a semaphore. | show 🗑
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| show | It ensures mutual exclusion.
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| How many philosophers at most may eat simultaneously in the Dining Philosophers problem with 5 philosophers? | show 🗑
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| show | executes as a single, uninterruptible unit
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| show | Several processes could be active in their critical sections at the same time.
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| show | It enters a synchronized method.
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| show | It exits a synchronized method.
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| show | The thread that has been waiting the longest becomes the new owner of the lock.
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| A semaphore ____. | show 🗑
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| show | does not require a context switch when a process must wait on a lock
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| In Peterson's solution, the ____ variable indicates if a process is ready to enter its critical section. | show 🗑
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| show | requires that no reader will be kept waiting unless a writer has already obtained permission to use the shared database.
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| show | monitor
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| show | every process in a set is waiting for an event that can only be caused by another process in the set
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| show | An unsafe state may lead to a deadlocked state.
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| show | It is not safe.
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| show | It is safe.
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| show | Available
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| show | R2, R1, R3.
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| A _____ could be preempted from a process. | show 🗑
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| show | Mutual Exclusion
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| The circular-wait condition for a deadlock implies the hold-and-wait condition. | show 🗑
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| One necessary condition for deadlock is ______, which states that a process must be holding one resource and waiting to acquire additional resources. | show 🗑
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| show | False
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| Protocols to prevent hold-and-wait conditions typically also prevent starvation. | show 🗑
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| The wait-for graph scheme is not applicable to a resource allocation system with multiple instances of each resource type. | show 🗑
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| show | False
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| show | True
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| show | False
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| Deadlock prevention and deadlock avoidance are essentially the same approaches for handling deadlock. | show 🗑
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| show | True
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| show | no preemption
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| One necessary condition for deadlock is ______, which states that there is a chain of waiting processes whereby P0 is waiting for a resource held by P1, P1 is waiting for a resource held by P2, and Pn is waiting for a resource held by P0. | show 🗑
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| The witness software product is a ____. | show 🗑
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| show | a directed edge from a process to a resource is called a request edge
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| show | a necessary and sufficient condition for a deadlock in the case that each resource has exactly one instance
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| show | pretend that deadlocks never occur
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| If the current value of counter = 5, what are its possible values if the producer consumer processes run concurrently? | show 🗑
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| What is the term for describing the situation where shared data may be manipulated concurrently and the outcome of the execution depends upon the order of access? | show 🗑
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| show | Critical Section
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| show | Mutual exclusion, Progress, Bounded waiting
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| A nonpreemptive kernel is essentially free from race conditions. | show 🗑
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| True or False? There are no guarantees Peterson's solution works correctly on modern computer architectures. | show 🗑
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| show | acquire() and release()
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| show | True
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| show | True
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| What are the two operations that can be performed on a semaphore? | show 🗑
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| A binary semaphore is functionally equivalent to a mutex lock. | show 🗑
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| show | Producer and Consumer
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| How many writers may concurrently share the database with the readers-writers problem? | show 🗑
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| show | Deadlock - each philosopher is waiting infinitely for the next.
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| What are the two operations that can be performed on a condition variable? | show 🗑
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| show | Java
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| show | Signaled, Nonsignaled
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| show | atomic_t type, atomic integers.
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| show | False. On single processor systems kernel preemption is enabled/disabled in place of acquiring/releasing a spinlock.
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| What are the Pthreads operations for locking and unlocking a mutex lock? | show 🗑
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| show | CPU-burst and IO-burst
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| Under preemptive scheduling, when a process switches from the running to the ready state, it may lose control of the CPU. | show 🗑
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| show | CPU utilisation (%), Throughput (# of processes completed), Turnaround time (time to complete a process), Waiting time (time spent in waiting in the ready queue), Response time (time from submission to first response)
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| What scheduling algorithm assigns the CPU to the process with the highest priority? | show 🗑
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| The multilevel feedback queue scheduling algorithm allows processes to migrate between different queues. | show 🗑
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| What scheduling algorithm assignments the CPU to the process that first requested it? | show 🗑
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| What scheduling algorithm assignments the CPU to a process for only its time slice (or time quantum)? | show 🗑
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| What scheduling algorithm assigns the CPU to the process with the shortest burst? | show 🗑
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| show | Process-contention scope, System-contention scope
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| show | test_and_set(), compare_and_swap()
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| show | True
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| What are the four necessary conditions for characterising deadlock? | show 🗑
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| Describe one strategy for dealing with deadlocks. | show 🗑
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| What is the only reasonable condition that can be used to prevent deadlocks from occurring? | show 🗑
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| show | Safe state
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| What is the name of the classic deadlock avoidance algorithm? | show 🗑
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| show | True
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| Provide at least one method for recovering from deadlock. | show 🗑
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| show | Relocation register, Limit register
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| show | Compile time, Load time, Execution time
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| show | False. An address generated by the CPU is a logical or virtual address, an address in memory is a physical address
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| What is the hardware device that maps virtual to physical addresses? | show 🗑
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| What is the backing store? | show 🗑
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| Mobile systems typically use swapping. | show 🗑
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| What are the three strategies for selecting a free hole from the set of available holes? | show 🗑
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| show | External fragmentation, Internal fragmentation
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| List at least two possible parts of a program that may be assigned separate segments. | show 🗑
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| What are the two parts of an address generated by the CPU? | show 🗑
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| show | The base address of each page in physical memory.
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| show | True. Internal fragmentation can occur. External cannot.
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| show | TLB miss. A memory reference to the page table is made, and the page and frame number are added to the Translation Look-aside Buffer (TLB)
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| What are frame protection bits? | show 🗑
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| show | Reentrant. I.e. code is non-self modifying: it never changes during execution.
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| List the three common Page Table Structures. | show 🗑
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| Assume an adaptive mutex is used for accessing shared data on a Solaris system with multiprocessing capabilities. Which of the following statements is not true? | show 🗑
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| show | performs a single logical function
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| show | True
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| Mutex locks and binary semaphores are essentially the same thing. | show 🗑
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| Monitors are a theoretical concept and are not practiced in modern programming languages | show 🗑
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| Race conditions are prevented by requiring that critical regions be protected by locks. | show 🗑
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| Which of the following statements is NOT true? | show 🗑
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| show | True
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| A deadlock-free solution eliminates the possibility of starvation. | show 🗑
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| show | serial schedule
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| The value of a counting semaphore can range only between 0 and 1. | show 🗑
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| Every object in Java has associated with it a single lock. | show 🗑
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| Windows XP, when accessing a global variable on a uniprocessor system, ____. | show 🗑
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| In multithreaded programs, the kernel informs an application about certain events using a procedure known as a(n) ____. | show 🗑
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| show | False
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| show | False
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| Fragmentation does not occur in a paging system. | show 🗑
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| show | 13
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| _____ is the dynamic storage-allocation algorithm which results in the largest leftover hole in memory. | show 🗑
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| A(n) ______ matches the process with each entry in the TLB. | show 🗑
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| Which of the following data structures is appropriate for placing into its own segment? | show 🗑
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| show | segment number and offset
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| show | compile-time binding
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| Reentrant code cannot be shared. | show 🗑
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| Hashed page tables are commonly used when handling addresses larger than 32 bits. | show 🗑
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| Hashed page tables are particularly useful for processes with sparse address spaces. | show 🗑
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| The mapping of a logical address to a physical address is done in hardware by the ________. | show 🗑
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| Suppose a program is operating with execution-time binding and the physical address generated is 300. The relocation register is set to 100. What is the corresponding logical address? | show 🗑
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| _____ is the method of binding instructions and data to memory performed by most general-purpose operating systems. | show 🗑
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| show | True
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| show | execution time
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| A relocation register is used to check for invalid memory addresses generated by a CPU. | show 🗑
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| show | False
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| Assume a system has a TLB hit ratio of 90%. It requires 15 nanoseconds to access the TLB, and 85 nanoseconds to access main memory. What is the effective memory access time in nanoseconds for this system? | show 🗑
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| show | 0xAE
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| show | 0xF9
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| Consider a logical address with 18 bits used to represent an entry in a conventional page table. How many entries are in the conventional page table? | show 🗑
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| show | It is possible only if relocation is dynamic and done at execution time.
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| show | Best fit
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| show | True
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| The roll out, roll in variant of swapping is used ____. | show 🗑
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| show | inverted
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| show | a stub is included in the image for each library-routine reference
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| show | 1200
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| show | 9
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| show | logical address
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| show | TLB reach
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| show | False
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| show | LRU
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| show | 64KB
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| show | for some page replacement algorithms, the page-fault rate may increase as the number of allocated frames increases
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| show | False
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| show | True
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| show | False
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| show | False
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| Which of the following statements is false with regard to allocating kernel memory? | show 🗑
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| show | proportional
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| Suppose we have the following page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and that there are three frames within our system. Using the FIFO replacement algorithm, what will be the final configuration of the three frames following the execution of the given | show 🗑
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| ______ allows a portion of a virtual address space to be logically associated with a file. | show 🗑
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| ________ allows the parent and child processes to initially share the same pages, but when either process modifies a page, a copy of the shared page is created. | show 🗑
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| Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and a system with three page frames, what is the number of page faults for the given reference string, using the LRU page-replacement algorithm? | show 🗑
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| Optimal page replacement ____. | show 🗑
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| show | True
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| show | True
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| show | True
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| show | Thrashing
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| Given the reference string of page accesses: 1 2 3 4 2 3 4 1 2 1 1 3 1 4 and a system with three page frames, what is the final configuration of the three frames after the true LRU algorithm is applied? | show 🗑
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| show | physical memory is separated from logical memory.
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| The _____ is an approximation of a program's locality. | show 🗑
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| The vfork() system call in UNIX ____. | show 🗑
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| show | False
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| show | All of the above
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| show | 0,0
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| show | The speed at which pages are examined (the scanrate) is constant.
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| show | False
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| Solaris, Windows XP, and Linux assign higher-priority threads/tasks longer time quantums and lower-priority tasks shorter time quantums. | show 🗑
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| In preemptive scheduling, the sections of code affected by interrupts must be guarded from simultaneous use. | show 🗑
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| Load balancing is typically only necessary on systems with a common run queue. | show 🗑
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| A Solaris interactive thread with a time quantum of 80 has a higher priority than an interactive thread with a time quantum of 120. | show 🗑
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| show | average waiting time in the queue
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| In Little's formula n = λ x W, what does λ represent ? | show 🗑
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| In Little's formula n = λ x W, what does n represent ? | show 🗑
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| show | throughput
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| In Solaris, if an interactive thread with priority 25 is waiting for I/O, what is its priority recalculated to when it is eligible to run again? | show 🗑
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| show | 5
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| show | nice
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| show | RR
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| With _______ a thread executes on a processor until a long-latency event (i.e. a memory stall) occurs. | show 🗑
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| The most complex scheduling algorithm is the multilevel feedback-queue algorithm. | show 🗑
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| A Solaris interactive thread with priority 15 has a higher relative priority than an interactive thread with priority 20 | show 🗑
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| ____ scheduling is approximated by predicting the next CPU burst with an exponential average of the measured lengths of previous CPU bursts. | show 🗑
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| ______ allows a thread to run on only one processor. | show 🗑
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| Round-robin (RR) scheduling degenerates to first-come-first-served (FCFS) scheduling if the time quantum is too long. | show 🗑
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| Systems using a one-to-one model (such as Windows XP, Solaris 9, and Linux) schedule threads using process-contention scope (PCS). | show 🗑
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| A significant problem with priority scheduling algorithms is _____. | show 🗑
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| show | FCFS
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| The ______ occurs in first-come-first-served scheduling when a process with a long CPU burst occupies the CPU. | show 🗑
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| show | A process keeps the CPU until it releases the CPU either by terminating or by switching to the waiting state.
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| Load balancing algorithms have no impact on the benefits of processor affinity. | show 🗑
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| show | System-contention scope
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| Virtualization does not allow a single-CPU system to appear as a multiprocessor system. | show 🗑
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| show | 14
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| What is the numeric priority of a Windows XP thread in the NORMAL_PRIORITY_CLASS with HIGHEST relative priority? | show 🗑
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| show | 6
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| show | Each queue has its own scheduling algorithm.
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| show | False
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| SMP systems that use multicore processors typically run faster than SMP systems that place each processor on separate cores. | show 🗑
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| show | 80
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| show | time sharing
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| Which of the following data structures in the banker's algorithm is a vector of length m, where m is the number of resource types? | show 🗑
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| ____________ occurs when a higher-priority process needs to access a data structure that is currently being accessed by a lower-priority process. | show 🗑
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| show | Operations on atomic integers do not require locking.
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| show | memory transaction
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| The OpenMP #pragma omp critical directive ___________. | show 🗑
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| show | indefinite blocking
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| show | A process keeps the CPU until it releases the CPU either by terminating or by switching to the waiting state.
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| Which of the following statements are false with regards to the Linux CFS scheduler? | show 🗑
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| show | targeted latency
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| show | 1/p
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| Which of the following is true of the rate-monotonic scheduling algorithm? | show 🗑
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| show | When a process becomes runnable, it must announce its deadline requirements to the system.
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| show | push migration, pull migration
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| show | All of the above
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| show | when a process exceeds its working set maximum
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| Systems in which memory access times vary significantly are known as __________. | show 🗑
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| show | no memory fragmentation
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