Exam 2 (Wkst Questions)

Given the following table; TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit Which row (by number) represents a represents the best performance?

1

Given the following table; TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit Which row (by number) represents the best case in terms of performance?

1

Given a fixed partitioning scheme with equal-size partitions of 2048 bytes and a total main memory size of 224 bytes. A page table is maintained that includes a pointer to a physical page for each resident process. How many bits are required for the pointer?

13

If the page size is 8192, how many bits are required for the page offset? 10 11 12 13

13

Given the following table; TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit Which row (by number) represents the worst case in terms of performance?

2

Given the following table; TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit Which row (by number) represents a page fault?

3

What is the purpose of a Translation Lookaside Buffer (TLB)? Decreases paging associated with compulsory misses. Increases associativeity for paging operations. Supports page table looking operations. A dedicated cache that contains those page table entries that have been most recently used.

A dedicated cache that contains those page table entries that have been most recently used.

What is the purpose of a Translation Lookaside Buffer (TLB)? Decreases paging associated with compulsory misses. Increases associativeity for paging operations. Supports page table looking operations. A dedicated cache that contains those page table entries that have been most recently used.

A dedicated cache that contains those page table entries that have been most recently used.

Why might a scheduling algorithm on a server system differ from a scheduling algorithm on a desktop system? A server must be able to handle more jobs and more cores which requires a fundamentally different approach for a scheduling algorithm. A desktop could more easily suspend background jobs. A server might focus on response time and a desktop might focus on throughput. A desktop might focus on response time and a server might focus on throughput.

A desktop might focus on response time and a server might focus on throughput.

What is paging? Only implemented on high-end server systems (i.e., super computer centers). Is the software implementation of the hardware device that at run time maps virtual address to physical address A memory compaction process that eliminates the problems associated with contiguous memory allocation. A memory management scheme that allows processes physical memory to be discontinuous.

A memory management scheme that allows processes physical memory to be discontinuous.

When a currently executing process uses its maximum allowed CPU time, what happens? If other cores are currently free, the process time limit is re-set. The process is terminated. The OS scheduler is invoked and the scheduler may allow the process to retain the CPU core. A process context switch is invoked.

A process context switch is invoked.

When a page fault occurs, the process requesting the page must block while waiting for the page to be brought from secondary storage into physical memory. Assume that there exists a process with five threads. If one thread incurs a page fault while accessing its data, will the other user threads belonging to the same process also be affected by the page fault — that is, will they also have to wait for the faulting page to be brought into memory? Yes. No. A thread would only be blocked if that thread attempted to access that memory. They will be blocked, but it is unrelated to the page fault. None of these answers are fully correct.

A thread would only be blocked if that thread attempted to access that memory.

With regard to address binding, match the correct columns. Compile time. Load time. Execution Time.

Absolute code. Relocatable code. DLL's/SO's

Which of the following are contiguous memory allocation strategies. First fit. Best fit. Worst fit. All of these answers are correct.

All of these answers are correct.

Which of the following is true regarding a priority scheduling algorithm. Check all that apply. All processes are not treated equally (for scheduling). Each process gets a small amount CPU time (time slice). Shares some characteristics with a first-come, first-served (FCFS) algorithm. Possible starvation for low priority processes. All processes are treated equally (for scheduling).

All processes are not treated equally (for scheduling). Each process gets a small amount CPU time (time slice). Possible starvation for low priority processes.

ready->running running->ready or blocked blocked->ready If the thread change state if it incurs a page fault > what state would it change to?

BLOCKED

ready->running running->ready or blocked blocked->ready If the thread change state when it generates a TLB miss that is resolved in the page table -> what state would it change to?

BLOCKED

Which of the following are criteria for which scheduling decisions could be based on? Check all that apply. CPU Utilization. Throughput. Turn-around time. Waiting time. Response time.

CPU Utilization. Throughput. Turn-around time. Waiting time. Response time.

A process that performs a large number of calculations is referred to as

Compute bound

The term late binding is typically associated with which of the following? Both soft and hard page faults. Hard page faults. Soft page faults. DDL/SO functions.

DDL/SO functions.

Which of the following is true regarding a round-robin scheduling algorithm. Check all that apply. All processes are not treated equally (for scheduling). Each process gets a small amount CPU time (time slice). Possible starvation for low priority processes. Shares some characteristics with a first-come, first-served (FCFS) algorithm. All processes are treated equally (for scheduling).

Each process gets a small amount CPU time (time slice). Shares some characteristics with a first-come, first-served (FCFS) algorithm. All processes are treated equally (for scheduling).

Which of the following is/are true regarding paging? Check all that apply. Is the modern version of the first fit memory allocation strategy. Requires a page size of 4096. Eliminates most of the problems of contiguous memory allocation. Works due to the principal of locality.

Eliminates most of the problems of contiguous memory allocation. Works due to the principal of locality.

Which of the following are considered goals of an OS scheduler? Check all that apply. Ensure fairness. Starvation freedom. Good response time. Implement preemption. Policy enforcement.

Ensure fairness. Starvation freedom. Good response time. Policy enforcement.

Which of the following is a key problem with contiguous memory allocation strategies. No specific issue, but provides overall less performance than other approaches. Seperation of data and code. Fragmentation. Limits implementation of segmentation.

Fragmentation

Which of the following is contained in the page/swap file? A subset of the swapped out pages for the executing process. Dirty data pages from the executing process (since instruction pages do not change). Full copy of the executing process. Swapped out pages of the executing process.

Full copy of the executing process.

What is meant by a hard real time system? Scheduling algorithms that execute in a timed, scheduled manner. Guaranteed to meet any scheduling requirements (within certain limits). Refers to the notion that the kernel tries to schedule applications within timing deadlines, but the kernel does not promise to always achieve these goals. None of these responses are fully correct.

Guaranteed to meet any scheduling requirements (within certain limits).

Which of the following is true regarding the memory management unit (MMU)? Improves overall performance since since most programs exhibit both temporal and spatial locality. Performs the hardware implementation for DLL's or SO's. Addresses generated by the process. Hardware that, at run time, helps maps virtual address to physical address.

Hardware that, at run time, helps maps virtual address to physical address.

A process that performs a large number amount of I/O is referred to as

I/O bound.

What is temporal locality? A reference to cache management protocols. If an item is referenced, items whose addresses are close by will tend to be referenced soon. If an item is referenced, it will tend to be referenced again soon. Programs access a relatively small portion of their address space at any instant of time. None of these answers are fully correct.

If an item is referenced, it will tend to be referenced again soon.

What is spatial locality? A reference to cache management protocols. If an item is referenced, items whose addresses are close by will tend to be referenced soon. If an item is referenced, it will tend to be referenced again soon. Programs access a relatively small portion of their address space at any instant of time. None of these answers are fully correct.

If an item is referenced, items whose addresses are close by will tend to be referenced soon.

Under what circumstance might a call to a library function (from a DLL/SO library) cause a soft fault? Such a call will not cause a page fault. It will always cause a page fault (which might be soft or hard). If the DLL/SO function being called is currently in memory. If the DLL/SO function being called is not currently in memory.

If the DLL/SO function being called is currently in memory.

Under what circumstance might a call to a library function (from a DLL/SO library) cause a hard fault? Such a call will not cause a page fault. It will always cause a page fault (which might be soft or hard). If the DLL/SO function being called is currently in memory. If the DLL/SO function being called is not currently in memory.

If the DLL/SO function being called is not currently in memory.

Which of the following is true regarding swapping? The need for swapping has been elminated by the availability of cheap RAM storage. All modeern OS's use swapping due to its very high performance. Is part of the hardware that, at run time, maps virtual address to physical address. If there is not enough memory available to keep all running processes in memory at the same time, then some processes who are not currently using the CPU may have their memory swapped out to a secondary storage called the backing store.

If there is not enough memory available to keep all running processes in memory at the same time, then some processes who are not currently using the CPU may have their memory swapped out to a secondary storage called the backing store.

What is the purpose of a Translation Lookaside Buffer (TLB)? Reduce compulsory misses in main memory. Implement security protocols for main memory to ensure appropriate memory segmentation. Improve performance by reducing having to go to disk to retrieve a page table entry. To provide for efficient use of main memory for process execution.

Improve performance by reducing having to go to disk to retrieve a page table entry.

In the context of paging, which is true regarding a hard (or major) fault? Check all that apply. Indicates that the page was placed into the free list and subsequently swapped out. Indicates that the page was placed into the free list but not yet swapped out. The page is not in memory and needs to be read from secondary storage. The page is already in memory and does not need to be read from secondary storage. None of these answers are fully correct.

Indicates that the page was placed into the free list and subsequently swapped out. The page is not in memory and needs to be read from secondary storage

In the context of paging, which is true regarding a soft (or minor) fault? Check all that apply. Indicates that the page was placed into the free list and subsequently swapped out. Indicates that the page was placed into the free list but not yet swapped out. The page is not in memory and needs to be read from secondary storage. The page is already in memory and does not need to be read from secondary storage. None of these answers are fully correct.

Indicates that the page was placed into the free list but not yet swapped out. The page is already in memory and does not need to be read from secondary storage.

Which of the following is true regarding processor cache configurations? Check all that apply. L1 is shared between all cores. L3 must be included in processes to ensure cache functionality. L1 is split into L1 Data and L1 Instruction caches. If an L3 is present, L2 may be per core. If an L3 is present, L2 may be shared.

L1 is split into L1 Data and L1 Instruction caches. If an L3 is present, L2 may be per core. If an L3 is present, L2 may be shared.

Given the following table; TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit Note which rows are legal or illegal.

Legal Legal Illegal Illegal

What would be an appropriate application for static partitioning? General use computing. Large scale computing (i.e., super computers) with limited job mixes. Many embeded systems. Older small systems, with limited functionality that only allow a limited number of processes.

Many embeded systems.

The scheduling criteria waiting time is defined as what? Very easy to implement. Keep CPU as busy as possible. Get as many jobs done per unit time as possible. Minimize time spent waiting in the ready queue for ready processes.

Minimize time spent waiting in the ready queue for ready processes.

Is it necessary for all of the pages of a process to be in main memory while the process is executing? Must all of the pages of a process in main memory be contiguous? Must the virtual pages be in a specific order?

No No Yes No

Which of the following scheduling criteria is more important. Throughput. Response time. Minimum time spent waiting in ready que None of these answers are correct.

None of these answers are correct.

Why might a process involuntarily give up the CPU? Assume a non-preemptive environment. Check all that apply. A higher priority process enters the system. The processes requests an I/O operaton. The processes time slice expires. The processes I/O request is completed. The process terminates. None of these responses are fully correct.

None of these responses are fully correct.

Which of the following describes the scheduling in a batch system? Check all that apply. Preemptive. Nonpreemptive. Allows multiple simultaneous use of resource (i.e., CPU core). First-come, first-served (FCFS) or first-in-first-out (FIFO) .

Nonpreemptive. First-come, first-served (FCFS) or first-in-first-out (FIFO) .

Which of the following is true regarding a physical address? Check all that apply. Visible to the process. Not visible to the process. Is generated by the program. Is seen by the memory hardware.

Not visible to the process. Is seen by the memory hardware.

Which of the following describes scheduling in an interactive system? Check all that apply. Preemptive. Nonpreemptive. Allows sharing of resource (i.e., CPU core). First-come, first-served (FCFS) or first-in-first-out (FIFO) .

Preemptive. Allows sharing of resource (i.e., CPU core).

What does it mean for a scheduling system to be preemptive? Check all that apply. Proceeses are allow to run for some maximum allowed time (time-slice). Select the next process to schedule when current process blocks. Processes are preempted in order to more effectively share the CPU core. Processes are not prempted and they execute until completion.

Proceeses are allow to run for some maximum allowed time (time-slice). Select the next process to schedule when current process blocks. Processes are preempted in order to more effectively share the CPU core.

What is the principal of locality? A reference to cache management protocols. If an item is referenced, items whose addresses are close by will tend to be referenced soon. If an item is referenced, it will tend to be referenced again soon. Programs access a relatively small portion of their address space at any instant of time. None of these answers are fully correct.

Programs access a relatively small portion of their address space at any instant of time.

ready->running running->ready or blocked blocked->ready If the thread change state when a page fault is resolved -> what state would it change to?

READY

What is meant by a soft real time system? Scheduling algorithms that execute in a timed, scheduled manner. Guaranteed to meet any scheduling requirements (within certain limits). Refers to the notion that the kernel tries to schedule applications within timing deadlines, but the kernel does not promise to always achieve these goals. None of these responses are fully correct.

Refers to the notion that the kernel tries to schedule applications within timing deadlines, but the kernel does not promise to always achieve these goals.

Which of the following are scheduling algorithms for an interactive system? Check all that apply. Round-robin scheduling. Priority scheduling. Shortest remaining time. Multiple queue scheduling. Random scheduling.

Round-robin scheduling. Priority scheduling. Shortest remaining time. Multiple queue scheduling.

What does it mean for a scheduling system to be nonpreemptive? Check all that apply. Proceeses are allow to run for some maximum allowed time (time-slice). Select the next process to schedule when current process blocks. Processes are preempted in order to more effectively share the CPU core. Processes are not prempted and they execute until completion.

Select the next process to schedule when current process blocks. Processes are not prempted and they execute until completion.

A process that executes in the background is referred to as what? Check all that apply. Magic. Service. Virus Daemon.

Service Daemon

Which of the following scheduling algorithms are typically associated with a batch environment? Check all that apply. Multiple queue scheduling. Round-robin scheduling. Shortest job next (SJN). First-come, first-served (FCFS) or first-in-first-out (FIFO) . Random scheduling.

Shortest job next (SJN). First-come, first-served (FCFS) or first-in-first-out (FIFO) .

The xv6 OS uses a state called RUNABLE. What does this mean? The process is being admitted into the system. The process is ready to be executed. The process is being executed. The process is waiting an I/O operation to be completed. The process is terminating. None of these responses are fully correct.

The process is ready to be executed.

If a process is blocked, what does that mean? The process is being admitted into the system. The process is ready to be executed. The process is being executed. The process is waiting an I/O operaton to be completed. The process is terminating. None of these responses are fully correct.

The process is waiting an I/O operaton to be completed.

Why might a process involuntarily give up the CPU? Assume a preemptive environment. Check all that apply. A higher priority process enters the system. The process terminates. The processes requests an I/O operaton. The processes time slice expires. The processes I/O request is completed. None of these responses are fully correct.

The processes time slice expires.

Which of the following are criteria for which scheduling decisions could be based on? Check all that apply. Security enforcement. Throughput . Response time. Policy enforcement. CPU Utilization.

Throughput. Response time. CPU Utilization.

The maximum allowed CPU time a process is allowed to execute (per turn using the CPU core) is referred to as what? Check all that apply. Iota. Time slice. Interval. Quantum.

Time slice. Quantum.

What is the purpose or goal of paging? Reduce compulsory misses in main memory. Implement security protocols for main memory to ensure appropriate memory segmentation. Increase memory performance for executing processes. To provide for efficient use of main memory for process execution.

To provide for efficient use of main memory for process execution.

Which of the following is true regarding a logical or virtual address? Check all that apply. Visible to the process. Not visible to the process. Is generated by the program. Is seen by the memory hardware.

Visible to the process. Is generated by the program.

When might a call to a library function cause a page fault? It is unlikely a basic function call will cause a page fault. Function calls only cause sotft faults (not hard faults). When that function is on a page that is not currently in memory. Only when the call is to a function in a DLL/SO.

When that function is on a page that is not currently in memory.

ready->running running->ready or blocked blocked->ready Will the thread change state if it generates a TLB miss that is resolved in the page table?

Yes

ready->running running->ready or blocked blocked->ready Will the thread change state if it incurs a page fault?

Yes

ready->running running->ready or blocked blocked->ready Will the thread change state when a page fault is fully resolved?

Yes

Broadly speaking, most processes ______________. are preemptive. are compute bound. are I/O bound. alternate between bursts of computing and I/O (disk or network).

alternate between bursts of computing and I/O (disk or network).

Given the following table, note which set of circumstances is possible. TLB Page Table Data Cache hit hit hit hit hit miss miss miss miss miss miss hit

yes yes yes no