CMPE320 EXAM 2

Describe two methods for eliminating processes by aborting a process

1. Abort all deadlocks at same time 2. Abort all processes one by one

Process vs Thread

A process is an executing program. A thread runs within the context of a process.

Peterson's Solution

A simple solution to the Critical Section problem where there is a flag to indicate whose turn of two processes in the critical section it is

The rate of a periodic task in a hard real-time system is ___, where p is period and t is processing time. A. 1/p B. p/t C. 1/t D. pt

A. 1/p

In system employing segmentation scheme for memory management wasted space is due to ___ A. External Fragmentation B. Frames of different sizes C. Internal Fragmentation D. Segments of Different Sizes

A. External FRagmentation

Main memory divided into a number of static partitions at system generation time is ___ A. Fixed Partitioning B. Simple Segmentation C. Dynamic Partitioning D. Simple Paging

A. Fixed Partitioning

One necessary condition for deadlock is ___, which states that a process must be holding one resource and waiting to acquire additional resources. A. Hold and Wait B. Mutual Exclusion C. Circular Wait D. No Preemption

A. Hold and Wait

The mapping of a logical address to a physical address is done in hardware by ___. A. Memory Management Unit B. Memory Address Register C. Relocation REgister D. Dynamic Loading REgister

A. Memory Management Unit

To handle deadlocks, operating systems most often A. Pretend the deadlocks never occur B. Use protocols to prevent or avoid deadlocks C. Detect and recover from deadlocks D. None of the above

A. Pretend the deadlocks never occur

___ allows a thread to run on only one processor A. Processor Affinity B. Processor Set C. NUMA D. Load Balancing

A. Processor Affinity

The fastest form of interprocess communication provided by UNIX is ___ A. Shared Memory B. Message C. Pipe D. Semaphore

A. Shared Memory

Which of the following is true of earliest-deadline-first (EDF) scheduling algorithm? A. When a process becomes runnable, it must announce its deadline requirements to the system. B. Deadlines are assigned as following: The earlier the deadline the lower the priority; the later the deadline the higher the priority. C. Priorities are fixed; that is, they cannot be adjusted when a new process starts running D. It assigns priorities statically according to deadline

A. When a process becomes runnable, it must announce its deadline requirements to the system.

Explain Round Robin (RR) Scheduling

Algorithm has a quantum time and takes turns running each job in the order they arrived for the length of the quantum time.

Aging

As time progresses increase the priority of the process to avoid starvation

The page table for each process maintains ___. A. The physical memory location of the process B. The frame location for each page of the process C. The page location for each frame of the process D. The logical memory location of the the process

B

A cycle in a resource-allocation graph is, ___ A. A necessary and sufficient condition for deadlock in the case that each resource has more than one instance. B. A necessary and sufficient condition for a deadlock in the case that each resource has exactly one instance C. A sufficient condition for a deadlock in the case that each resource has more than one instance D. Is neither necessary nor sufficient for indicating deadlock in the case that each resource has exactly one instance.

B. A necessary and sufficient condition for a deadlock in the case that each resource has exactly one instance

Which of the following is true of cooperative scheduling? A. It requires a timer B. A process keeps the CPU until it releases the CPU either by terminating or by switching to a waiting state C. It incurs a cost associated with access to shared data D. A process switches from running state to the ready state when an interrupt occurs.

B. A process keeps the CPU until it releases the CPU either by terminating or by switching to a waiting state.

In Little's formula, λ represents the ___ A. Average waiting time in the queue B. Average arrival rate for new processes in the queue C. Average queue length D. Average CPU utilization

B. Average arrival rate for new processes in the queue.

___ is the dynamic storage allocation algorithm which results in the smallest leftover hole in memory. A. First Fit B. Best Fit C. Worst Fit D. None of the above

B. Best Fit

One technique for overcoming external fragmentation is ___. A. Loading B. Compaction C. Relocation D. Partitioning

B. Compaction

The ___ determines when a page should be brought into memory A. Page Fault B. Fetch Policy C. Working Set D. Resident Set Management

B. Fetch Policy

An address generated by a CPU is known as A. Physical Address B. Logical Address C. Post Relocation Register Address D. Memory Management Unit Generated Address

B. Logical Address

One necessary condition for a deadlock is ___, which states that at least one resource must be held in a nonsharable mode. A. Hold and Wait B. Mutual Exclusion C. Circular Wait D. No Preemption

B. Mutual Exclusion

With ____ only one process may use a resource at a time and no process may access a resource unit that has been allocated to another process A. Hold and Wait B. Mutual Exclusion C. No Preemption D. Circular Wait

B. Mutual Exclusion

___ is transparent tot the programmer and eliminates external fragmentation providing efficient use of the main memory A. Hashing B. Piping C. Segmentation D. Thrashing

B. Piping

___ involves the decision of which kernel thread to schedule onto which CPU A. Process-contention scope B. System-contention scope C. Dispatcher D. Round-robin scheduling

B. System-contention scope

In a system employing segmentation scheme for memory management a process is divided into ___. A. One segment per thread B. A number of threads C. A number of segments which need not be of equal size D. A number of segments which must be of equal size

C

In a system resource-allocation graph, ___. A. A directed edge from a process to a resource is called an assignment edge B. A directed edge from a resource to a process is called a request edge. C. A directed edge from a process to a resource is called a request edge D. None of the above

C. A directed edge from a process to a resource is called a request edge

Which of the following is true of the rate-monotonic scheduling algorithm? A. The task with the shortest period will have the lowest priority. B. It uses a dynamic priority policy. C. CPU utilization is bounded when using the algorithm D. It is non-preemptive

C. CPU utilization is bounded when using the algorithm

A closed chain of processes exists, such that each process holds at least one resource needed by the next process in the chain is the condition of ___. A. No Preemption B. Mutual Exclusion C. Circular Wait D. Hold and Wait

C. Circular Wait

The ___ occurs in FCFS scheduling when a process with a long CPU burst occupies the CPU. A. Dispatch Latency B. Waiting Time C. Convoy Effect D. System Contention Scope

C. Convoy Effect

A deadlocked state occurs whenever ___ A. A process is waiting for I/O device that does not exist B. The system has no available free resources C. Every process in a set is waiting for an event that can only be caused by another process in the set. D. A process is unable to release its request for a resource after use

C. Every process in a set is waiting for an event that can only be caused by another process in the set.

Which of the following scheduling algorithms must be nonpreemptive? A. SJF B. RR C. FCFS D. Priority Algorithms

C. FCFS

In dynamic partitioning technique of memory management, the placement algorithm that scans memory from the location of the last placement and chooses the next available block that is large enough to be satisfy is called ___. A. Last Fit B. Best Fit C. Next Fit D. First Fit

C. Next Fit

A ___ is issued if a desired page is not in main memory. A. Paging Error B. Page Replacement Policy C. Page Fault D. Page Placement Policy

C. Page Fault

The ___ scheduling algorithm is designed especially for time-sharing systems. A. SJF B. FCFS C. RR D. Multilevel queue

C. RR

The address of a storage location in main memory is the ___. A. Address Space B. Virtual Address Space C. Real Address D. Virtual Address

C. Real Address

A significant problem with priority scheduling algorithm is ___ A. Complexity B. Starvation C. Determining the length of the next CPU burst D. Determining the length of the time quantum

C. Starvation

With ___ a process is loaded by loading all of its segments into dynamic partitions that do not need to be contingous A. Simple Paging B. Virtual Memory Segmentation C. Virtual Memory Paging D. Simple Segmentations

C. Virtual Memory Paging

What is the scheduling criteria of a CPU?

CPU Utilization: Keep the CPU as busy as possible Throughput: # of processes that complete their execution per time unit Turnaround Time: Amount of time to execute a particular process Waiting Time: Amount of time a process has been waiting in the ready queue. Response Time: Amount of time it takes from when a request was submitted until the first response is produced, not output (for time-sharing environment)

The ___ binding scheme facilitates swapping A. Interrupt Time B. Load Time C. Assembly Time D. Execution Time

D

Assume there are three resources, R1, R2, and R3, that each assigned unique int values 15, 10, and 25 respectively. What is a resource ordering which prevents circular wait? A. R1 R2 R3 B. R3 R2 R1 C R3 R1 R2 D R2 R1 R3

D R2 R1 R3

Which of the following is true of compaction? A. It can be done at assembly, load, or execution time. B. It is used to solve the problem of internal fragmentation C. It cannot shuffle memory contents D. It is possible only if relocation is dynamic and done at execution time

D.

The concept of Memory Management satisfies certain system requirements including: A. Relocation B. Protection C. Physical Organization D. All of the Above

D. All of the above

A set of processes is ___ when each process in the set is blocked awaiting an event that can only be triggered by another blocked process in the set. A. Spinlocked B. Preempted C. Stagnant D. Deadlocked

D. Deadlocked

Which of the following is true of multilevel queue scheduling? A. Processes can move between queues. B. Each queue has its own scheduling algorithm C. A queue cannot have absolute priority over lower-priority queues. D. It is the most general CPU-scheduling algorithm

D. It is the most general CPU scheduling algorithm

The general two approaches to load balancing are ___ and ___ A. Soft Affinity and Hard Affinity B. Coarse Grained and Fine Grained C. Soft Real-Time and Hard Real-Time D. Push Migration and Pull Migration

D. Push Migration and Pull Migration

___ scheduling is approximated by predicting the next CPU burst with an exponential average of the measured lengths of previous CPU bursts A. Multilevel Queue B. RR C. FCFS D. SJF

D. SJF

___ is the number of processes that are completed per time unit. A. CPU Utilization B. Response Time C. Turnaround Time D. Throughput

D. Throughput

What are the advantages of the EDF Scheduling Algorithm over the Rate-Monotonic Schedulign Algorithm?

EDF does not require processes be periodic nor must a process require a constant amount of CPU time per burst

Round Robin Scheduling

Each process gets a small CPU unit time called a quantum time, and takes turns switching between processes.

What are the two types of latency that affect performance of real-time systems?

Event Latency Dispatch Latency

T/F Segmentation does not eliminate internal fragmentation

False

T/F The memory protection requirement must be satisfied by the OS rather than the processor.

False

How much does FCFS scheduling algorithms discriminate in favor of short processes?

If long processes gets in first, then later short ones will hang.

What effect does the size of the time quantum ahve on the performance of an RR algorithm.

If the quantum time is large, it is similar performance to FCFS. If the quantum time is small, then there will be a ton of context switches with the time sharing 1/n

How does SJF Scheduling change if you allow preemption?

If you allow preemption, then if a job arrives that is shorter than the current one running, it will interrupt the current job and run the new shorter job.

What is one way to ensure circular-wait condition does not occur?

Impose a total ordering of all resource types and require each process requests a resource in an increasing order of need.

Semaphore

Instead of locking the entire critical section to one buffer as Mutex does, split the section into multiple buffers.

Binary Semaphore

Integer value can range only between 0 and 1. Same as Mutex Lock

Counting Semaphore

Integer value can range over an unrestricted domain

Distinguish between internal fragmentation and external fragmentation

Internal fragmentation is the wasted space within each allocated block because of rounding up from the actual requested allocation to the allocation granularity. External fragmentation is the various free spaced holes that are generated in either your memory or disk space. External fragmented blocks are available for allocation, but may be too small to be of any use.

First Come First Serve (FCFS) Scheduling

Literally like a queue where the processes are executed in the order they come in.

Explain the basic method for implementing paging.

Main memory is divided into a number of equal-size frames. Each process is divided into a number of equal-size pages of the same length as the frames. A process is loaded by loading all of its pages available, not necessarily contiguous frames

What is paging?

Memory management without the need for contiguous memory allocation.

What is the Dispatcher?

Module gives control of the CPU to the process selected by the short-term scheduler.

Mutex Lock

Mutex Lock is simply a lock that is given to one process to access the critical section (ALL OF IT) at one time. EX: It is like a bathroom key

Describe the four conditions that must hold in a system if a deadlock is to occur

Mutual Exclusion Hold and Wait No Preemption Circular Wait

What are the three solutions to the Critical-Section Problem?

Mutual Exclusion Progress Bounded Waiting

Atomic

Non-interruptable

Explain the difference between preemptive and non-preemptive scheduling

Preemptive = Process can be interrupted Non-preemptive = Process cannot be interrupted

Preemptive vs Non-Preemptive

Preemptive is it tells a process it is interrupting it before it does. Non-preemeptive just interrupts it without saying anything

What is the difference between deadlock prevention and deadlock avoidance?

Prevention the goal is that none of the deadlock conditions can ever hold. It does not need prior info. Avoidance is to never enter and unsafe state and keep track of resources with prior info to prevent it.

Explain First Come First Serve (FCFS) Scheduling

Processes run in the order they arrive.

Locking

Protects the critical section

Multilevel Queue

Ready queue is partitioned into seperate queues. Foreground (interactive) Background (batch) Foreground give priority and then background/batch run when foreground isn't.

Why is a mutex lock called a spinlock as well?

Results in busy-waiting

How much do multilevel feedback queues scheduling algorithms discriminate in favor of short processes?

Same as Round Robin Short processes can finish early depending on the quantum time.

Priority Inversion

Scheduling problem when low priority process holds a lock needed for high priority process

Short-term scheduler

Selects from among the processes in ready queue and allocates the CPU to one of them.

Convoy Effect

Short Processes are behind Long Processes

How much does RR scheduling algorithms discriminate in favor of short processes?

Short processes can finish early depending on the quantum time.

Explain the process of starvation and how aging can be used to prevent it.

Starvation is when a low priority process is continuously blocked and indefinitely waiting. Aging solves this problem by increasing the priority as the algorithm waits longer.

What advantage is there in having different time-quantum sizes at different levels of multilevel queuing system?

The advantage is that only allot a large amount of CPU time to processes that are taking forever. So if a job is very short, it doesn't have any busy

What is a cycle when it comes to process execution

The going back and forth from a CPU Burst to an I/O Burst

Explain Shortest Job First (SJF) Scheduling

The job with the shortest burst time runs first.

Shortest Job First (SJF) Scheduling

The process with the shortest burst time will execute first. It will preempt when switching

Explain what has to happen for a set of processes to achieve a deadlocked state

There are a limited set of resources and a set of processes. They are in a cycle where one process is waiting for a resource held by another process, while that process is waiting for the resource that it currently holds.

What is Dispatch Latency

Time it takes for the dispatcher to stop one process and start another

T/F A mutex is used to ensure that only one thread at a time can access the resource protected by the mutex.

True

T/F Any protection mechanism must have the flexibility to allow several processes to access the same portion of memory.

True

T/F Programs in other processes should not be able to reference memory locations in a process for reading or writing purposes without permission

True

What is the equation for Turnaround Time?

Turnaround Time = Finish Time - Arrival Time

Deadlock

Two or more processes are waiting indefinitely for an event that can be caused by only one of the waiting processes

Consider a system implementing a multilevel queue scheduling. What strategy can a computer user employ to maximize the amount of CPU time allocated to the user's process?

Use most time quantum then stop

What is the equation for Waiting Time?

Waiting Time = Turnaround Time - Burst Time

What is a race condition?

When two or more processes are altering a critical section at one time.

Priority Scheduling

Where a process is given a priority based on some factor and scheduled to execute in that order.

Starvation

Where a process never has a high enough priority to access a resource

A CPU scheduling algorithm determines an order for the execution of its scheduled processes. Given n processes to be scheduled on one processor, how many different schedules are possible?

n!