FOR FREE MATERIALS
- Introduction: OS
- Booting Process
- Command Interpreter
- Dual mode of operation
- System Calls
- Difference between system call and library call
- Interrupt and Trap
- Introduction
- Scheduling Criteria, Terms and Concepts
- Different Type Scheduling Algorithms
- Longest Job First
- Longest Remaining Time First
- Highest Response Ratio Next (HRRN)
- Priority Scheduling
- Least Completed Next (LCN) Scheduling
- Multi-Level Queue Scheduling
- Multilevel Feedback Queue Scheduling
- Guaranteed Scheduling
- Fair Share Scheduling
- Lottery Scheduling
- Multi-Processor Scheduling
- Deadline Scheduling
- Rate-Monotonic Scheduling
- POSIX Real-Time Scheduling
- Priority Inversion
- Proportional Share Scheduling
- Comparison table of Scheduling Algorithm
- Algorithm Evaluation for Scheduling
- Important concept of MM
- Memory Representation as Address
- Memory layout for a Process
- Logical and Physical Address Space
- Necessity of Memory Management
- Introduction
- Concept of Non-contiguous memory allocation
- Basic concept of Paging
- Address Translation
- Process of Paging Method
- Calculation of Offset for paging
- Calculation of Logical Address Bit and number of Pages
- Calculation of Physical Address Bit and number of Frames
- Calculation of Page Table Size
- Organization of MMU
- Why Page size power of 2
- Paging Address Calculation: example1
- Paging Numeric Problem: Example2
- Paging Address Calculation: Example3
- Paging Address Calculation: Question1
- Some Important Question 2
- Paging Address Translation: Question3
- UGC NET Paging Question
- GATE Paging Question
- Number of information at Page Entry
- Exams Question on Page Entry Information
- Exam Question: Page Entry Information
- Calculates Page Table Entry Size
- Calculates Page Size
- Calculation of Optimal Page Size
- Question on Optimal Page Size
- Hashed Page Table with Example
- Inverted Page Table with Gate Question
- Question on Inverted Page Table
- Multi-Level Paging
- Multi-level paging: Example1
- Multi-level paging: Example2
- Allocation of Frames
- Subject Mock
Longest Remaining Time First (Preemptive LJF):
It is a preemptive version of Longest Job First.
Criteria: Burst Time + Arrival Time
Mode: Preemptive
Data Structure: Max Heap
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Gantt Chart:
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Number of Context Switching (CS) = 19 (Here time required for context switching is expensive)
Now we calculate Turn Around Time (TAT) and Waiting Time (WT) using the following formula:
TAT = CT - AT, WT = TAT – BT
And
Response Time (RT) = FR (First Response) - AR (Arrival Time)
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Advantages of LRTF
a. It corrects some of the weaknesses of both SJF and FCFS.
b. It tries to reduce overall turnaround time and maximize system utilization for
height system loads.
Disadvantage
a. Starvation of shorter job.
b. Low response time among several jobs.
Question. (GATE 2006)
Consider three processes (process id 0,1,2 respectively) with compute time bursts 2,4 and 8 - time units. All processes arrive at time zero. Consider the longest remaining time first (LRTF) scheduling algorithm. In LRTF ties are broken by giving priority to the process with the lowest process id. The average turnaround time is:
(a) 13 units
(b) 14 units
(c) 15 unit
(d) 16 unit
Answer:
As per question
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Gantt Chart:
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Now we calculate Turn Around Time (TAT) and Waiting Time (WT) using the following formula:
Turn Around Time = Completion Time - Arrival Time
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CT = TAT because AT = 0 for all process
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Option (a) correct.
