CS6200 Final Exam Review Part 3 - Scheduling Lesson 1
69 Questions
0 Views

Choose a study mode

Play Quiz
Study Flashcards
Spaced Repetition
Chat to Lesson

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

Who is the author of the CS6200 Final Exam Review guide?

  • An Udacity instructor
  • A current student
  • A professor
  • George Kudrayvtsev (correct)

What is the purpose of the formula 'derivations' in the context of scheduling metrics?

  • To calculate the completion time of tasks
  • To determine the queueing order of tasks
  • To generalize and understand each metric better (correct)
  • To compare scheduling algorithms

What does the variable Ti represent in the context of scheduling metrics?

  • The completion time of task i (correct)
  • The queueing order of task i
  • The execution time of task i
  • The number of tasks used for the metric

What is the ideal scenario for determining the completion time of tasks?

<p>When the task completion time is known prior to execution (A)</p> Signup and view all the answers

What is the variable n used to represent in the context of scheduling metrics?

<p>The number of tasks used for the metric (C)</p> Signup and view all the answers

What is the primary goal of considering various metrics when discussing scheduling?

<p>To compare the performance of different scheduling algorithms (A)</p> Signup and view all the answers

When is it beneficial to context switch between tasks?

<p>When 2t &lt; context switch &lt; tblocking task (D)</p> Signup and view all the answers

What is the purpose of a scheduler in scheduling tasks?

<p>To minimize the overhead of the interruption and algorithm (D)</p> Signup and view all the answers

Why are longer timeslices beneficial for CPU-bound tasks?

<p>They enable the task to make the most of its CPU time (D)</p> Signup and view all the answers

What is the advantage of shorter timeslices for I/O-bound tasks?

<p>They enable the task to respond to user requests (A)</p> Signup and view all the answers

What is the purpose of the multi-level feedback queue?

<p>To dynamically balance a task's timeslice based on its history (C)</p> Signup and view all the answers

What happens when a task yields voluntarily during its given timeslice?

<p>It belongs at that timeslice level (D)</p> Signup and view all the answers

What was the problem with the O(1) scheduler that led to the development of the CFS?

<p>It did not dynamically balance a task's timeslice (A)</p> Signup and view all the answers

What is the average completion time for the tasks T1, T2, and T3?

<p>11.4 s (A)</p> Signup and view all the answers

What is the CPU utilization for the tasks T1, T2, and T3?

<p>82% (D)</p> Signup and view all the answers

What is the average wait time for the tasks T1, T2, and T3?

<p>1.833 s (B)</p> Signup and view all the answers

What is the primary function of the vruntime in task scheduling?

<p>To adjust the running time of tasks based on their priority (D)</p> Signup and view all the answers

What is the time complexity of selecting a task in the scheduling algorithm?

<p>O(1) (C)</p> Signup and view all the answers

What is the metric proposed by Fedorova to measure the 'average instruction delay'?

<p>CPI (Cycles Per Instruction) (D)</p> Signup and view all the answers

What is the purpose of the 'dirty bit' in a page table entry?

<p>To indicate whether a page has been written to since it was loaded (D)</p> Signup and view all the answers

What happens when a process tries to access a page not present in physical memory?

<p>A page fault occurs and the OS handles it (D)</p> Signup and view all the answers

What is the purpose of page tables in memory management?

<p>To translate virtual addresses to physical addresses (A)</p> Signup and view all the answers

How does the OS map the memory allocated to a process to the underlying physical memory?

<p>Using a page table (A)</p> Signup and view all the answers

What is the role of the Memory Management Unit (MMU) in page tables?

<p>To perform the translation between virtual and physical addresses (A)</p> Signup and view all the answers

What is the purpose of the 'accessed bit' in a page table entry?

<p>To indicate whether a page has been accessed during some period of time (D)</p> Signup and view all the answers

What happens when a translation for a requested address is present in the page table but does not translate to an existing physical memory address?

<p>The data is moved from the disk to physical memory. (B)</p> Signup and view all the answers

What is the purpose of the 'copy-on-write' optimization in page tables?

<p>To allow multiple virtual address spaces to refer to the same physical pages. (D)</p> Signup and view all the answers

What is the result of an unintended unallocated access, such as dereferencing an invalid pointer?

<p>A segmentation fault is triggered and sent to the user process. (A)</p> Signup and view all the answers

Why is the 'not allowed' type of access critical for certain exploitation prevention techniques?

<p>It prevents unauthorized access to certain memory regions. (A)</p> Signup and view all the answers

What is the purpose of the access bit in the page table?

<p>To determine which page to replace in the page table. (A)</p> Signup and view all the answers

What is the result of a process accessing a page that is not in physical memory?

<p>The MMU issues a page fault to the operating system. (D)</p> Signup and view all the answers

What is the purpose of demand paging?

<p>To simulate a larger address space than is physically available. (A)</p> Signup and view all the answers

What is the role of the page replacement policy in demand paging?

<p>To decide which page to replace in the page table. (C)</p> Signup and view all the answers

What is the purpose of the dirty bit in the page table?

<p>To track which pages have been modified. (D)</p> Signup and view all the answers

How many entries does the second table have in the given memory addressing schema?

<p>4 (D)</p> Signup and view all the answers

What address space does a single inner-most page table address in the context given?

<p>64MiB of memory (B)</p> Signup and view all the answers

In the memory addressing schema discussed, how many layers are there in total?

<p>16 (C)</p> Signup and view all the answers

What does the parameter P3 index into in the given address chunking sequence?

<p>The third table (D)</p> Signup and view all the answers

How many bits are used for the offset in the virtual address chunking in the provided context?

<p>12 bits (B)</p> Signup and view all the answers

What does the Avg. Job Wait Time measure?

<p>The time it takes for a task to move from the 'queued' state to the 'executing' state (D)</p> Signup and view all the answers

What is the definition of CPU Utilization?

<p>The percentage of time that the CPU is using to do 'useful work' (C)</p> Signup and view all the answers

How is Avg. Job Completion Time calculated for a FCFS policy?

<p>$\frac{1}{n}\sum_{i=1}^{n}(n-i+1)Ti$ (D)</p> Signup and view all the answers

What is the primary purpose of understanding the derivation of the scheduling formulas rather than memorizing them?

<p>To synthesize the information for complex scenarios (A)</p> Signup and view all the answers

What triggers the scheduling algorithm to execute periodically?

<p>All of the above (D)</p> Signup and view all the answers

What does the CPU Utilization measure?

<p>The percentage of time the CPU is doing 'useful work' (C)</p> Signup and view all the answers

For Average Job Completion Time with SJF policy, what replaces Ti in the formula for FCFS?

<p>Cj (C)</p> Signup and view all the answers

What is the primary reason for placing importance on understanding the derivation of scheduling formulas?

<p>To synthesize information for more complex scenarios (C)</p> Signup and view all the answers

What data structure is closely associated with scheduling algorithms to enable specific decision-making?

<p>Runqueue (D)</p> Signup and view all the answers

What is the purpose of having a consistent, recurring interval for calculating CPU Utilization?

<p>To measure the percentage of useful work in small intervals (B)</p> Signup and view all the answers

In the Linux O(1) scheduler, what indicates a non-empty index in the array used for task selection?

<p>First set bit in a bitmap (A)</p> Signup and view all the answers

What is the range of priorities for tasks in the Linux O(1) scheduler?

<p>0 to 99 (D)</p> Signup and view all the answers

What happens when the timeslice of a task expires in the Linux O(1) scheduler?

<p>The task is moved to the expired array (A)</p> Signup and view all the answers

What is the main data structure used in the Linux CFS Scheduler?

<p>Red-Black Tree (C)</p> Signup and view all the answers

How is a task's priority adjusted based on its idle time in the Linux O(1) scheduler?

<p>Inversely proportional (A)</p> Signup and view all the answers

What is vruntime in the Linux CFS Scheduler proportional to?

<p>Time spent by a task on the CPU (B)</p> Signup and view all the answers

How does the Solaris scheduler handle I/O-bound tasks noticing a task yields often for its timeslice?

<p>Increases the timeslice (B)</p> Signup and view all the answers

Why did the O(1) scheduler become unacceptable as workloads changed?

<p>It caused unpredictable scheduling times (A)</p> Signup and view all the answers

What is the key difference between higher and lower priority tasks in the Linux O(1) scheduler?

<p>Higher priority tasks have lower priority values (D)</p> Signup and view all the answers

How does the Linux CFS scheduler ensure fairness among tasks?

<p>By using a red-black tree for task ordering (D)</p> Signup and view all the answers

In address translation, the purpose of the Translation Lookaside Buffer (TLB) is to:

<p>Translate virtual addresses to physical addresses quickly. (D)</p> Signup and view all the answers

What is the role of page table entries in address translation?

<p>Correlate virtual page numbers to physical page numbers. (B)</p> Signup and view all the answers

How does splitting a virtual address into multiple levels of page tables benefit memory management?

<p>Minimizes wasted space in page tables. (C)</p> Signup and view all the answers

What is the purpose of discretizing virtual addresses into virtual page numbers (VPNs)?

<p>To index into a page table. (C)</p> Signup and view all the answers

What is the relationship between address space and the physical memory size in address translation?

<p>The address space is independent of physical memory size. (D)</p> Signup and view all the answers

How does the page size influence the size of a page table?

<p>Larger page size leads to larger page tables. (D)</p> Signup and view all the answers

What happens in address translation after a virtual address is indexed into a page table?

<p>The offset is concatenated with the physical address. (D)</p> Signup and view all the answers

Why is hierarchical page table structure preferred for memory management?

<p>To reduce unnecessary page table entries and gaps. (A)</p> Signup and view all the answers

What purpose does the Translation Lookaside Buffer (TLB) serve in the context of address translation?

<p>It speeds up address translation by caching page table entries. (C)</p> Signup and view all the answers

What is the significance of the physical memory size in relationship to page table calculations?

<p>It is a crucial factor in calculating the required page table entries. (B)</p> Signup and view all the answers
Use Quizgecko on...
Browser
Open
Browser
Browser