Real-Time Operating Systems: Design and Implementation

Explore basic concepts of cpu scheduling on a single processor, including multiprogramming, cpu and io bursts, ready queue, and short-term scheduling with preemptive and non-preemptive modes.

Explore the first come, first served scheduling algorithm, its fifo queue implementation, and how arrival order affects waiting and turnaround times with convoy effects and examples.

Learn the shortest job first scheduling algorithm and its shortest remaining time first variant to minimize average waiting time using CPU burst lengths, with fcfs tie-breaking.

Learn priority scheduling, where the highest priority runs, aging prevents starvation, and both non-preemptive and preemptive versions are illustrated with a process example and a Gantt chart.

Explore the round robin scheduling algorithm in real-time systems with preemption, using a time quantum from 10 to 100 milliseconds, and analyze waiting times, turnaround times, and Gantt chart examples.

Explore the multilevel queue scheduling algorithm that partitions the ready queue into foreground and background queues, with foreground round robin and background first come first serve scheduling.

Explore multilevel feedback queue scheduling, which moves processes between three queues based on cpu burst, uses 8 ms and 16 ms round-robin, and fcfs, with aging to prevent starvation.

Explore how deadlocks arise in resource allocation, with four conditions, resource allocation graphs, and strategies for prevention, avoidance, detection, and recovery.

Apply deadlock prevention by enforcing hold-and-wait and no preemption strategies, and guard against circular wait with resource ordering. Compare allocation of all resources with releasing and re-requesting to avoid deadlock.

Explore how deadlock avoidance uses the maximum demands and a priori information, safety checks, resource allocation graphs, and the banker's algorithm to keep the system in a safe state.

Solve deadlock avoidance problems by computing the need matrix, applying the safety and resource request algorithms, and identifying safe states and sequences for granting requests.

Explore how deadlocks are detected using resource allocation and wait-for graphs, with a step-by-step detection algorithm using work and finish, and single versus multiple resource instances.

Recover from deadlock by terminating or preempting resources to break the cycle, considering process priority, runtime, resources held and needed, and rollback to a safe state to avoid starvation.

Explore how swapping moves data between main memory and secondary storage to manage limited RAM, enabling multiple processes via swap in/out while risking performance and data loss.

Explore contiguous memory allocation, including fixed and variable partitioning, and compare first fit, best fit, and worst fit algorithms to manage memory amid fragmentation and multiprogramming.

Explore paging as a non-contiguous memory management technique with fixed-size pages and frames, guided by per-process page tables and a TLB, handling page faults and fragmentation trade-offs.

Explore segmentation, a non-contiguous memory allocation technique using a segment table to map segments with base addresses and limits, and translate segment numbers and offsets to physical addresses.

Explain how a page fault occurs when the CPU references a page not in main memory, the OS fetches it from secondary memory, updates the page table, and restarts execution.

Virtual memory is a memory management technique that lets programs run larger than physical memory by separating logical and physical memory, using a page table and translation lookaside buffer.

Discover how demand paging loads pages on demand from secondary memory into main memory using a pager, with a page table and swap device, affecting the effective access time.

Discover how the fifo page replacement algorithm manages memory by using a queue to replace the oldest loaded page when frames are full, triggering page faults and hits.

Explain the optimal page replacement algorithm, which replaces a page not referred in the future to minimize page faults, with steps and a three-frame example.

Explore how the least recently used (LRU) page replacement algorithm selects a victim among three frames using reference strings, then counts page faults and hits to compute ratios.

Explore the least frequently used page replacement algorithm, a counting-based method that tracks reference frequencies, increments on access, and decrements on eviction. Tie-breaks rely on fifo, with hits and faults.

Learn how main memory is divided into frames and how allocation techniques, including equal, proportional, priority, global, and local, affect the page fault ratio and performance.

Explore thrashing by high multiprogramming and lack of frames, and how page faults swap between memory and secondary memory, affecting cpu utilization, with working set and page fault frequency models.

Explore disk scheduling and IO scheduling algorithms, including FCFS, SSTF, scan, c-scan, and look, to optimize disk access time and minimize seek delays.

Explore the FCFS disk scheduling algorithm in real-time operating systems, aiming to minimize seek time and latency while maximizing throughput, illustrated by a head movement sequence.

Explore the shortest seek time first disk scheduling algorithm, compare it with first-come-first-serve, and see how SSTF reduces latency and improves throughput through practical head-movement examples.

Apply the scan disk scheduling algorithm, where the disk arm moves to the end of the disk, reverses, and services requests along the path like an elevator.

The look disk scheduling algorithm moves toward larger requests, stops at the last one, reverses, and serves remaining requests without reaching the disk end, reducing arm movement and increasing throughput.

Explain how the c-scan disk scheduling algorithm increases throughput by sweeping from the header to the end, wrapping to zero, and serving requests with uniform wait time.

Explore the C-look disk scheduling algorithm, its left-to-right head movement, stopping at the last request, and how it reduces delay versus SCAN and C-SCAN.