Silberschatz and Galvin1999 7.1

Chapters 3 and 5

• Possible questions

– Tracing a given program involving fork, exec, semaphores, and share memory

– Wring a simple program using fork, exec, semaphores, and share memory

– Solving a synchronization problem using semaphores or monitors.

Silberschatz and Galvin1999 7.2

Chapter 7: Deadlocks

• Necessary Conditions for deadlock

• Modeling deadlock using Resource allocation graph

• Methods for handling deadlock

– Deadlock prevention Methods for preventing deadlocks (preventing hold and wait,

preventing no preemption, preventing circular wait) -- Section 7.4

– Deadlock avoidance Methods for avoiding deadlocks (Resouce allocation graph

algorithm, Banker’s algorithm) -- Section 7.5

– Deadlock detection and resolution Methods detecting deadlocks (Single instance resource type,

several instance resource type) -- Section 7.6

Silberschatz and Galvin1999 7.3

Chapter 8 – Main Memory

• Overlays, physical and logical address space

• Swapping

• Memory allocation for processes– Contiguous allocation – advantages and disadvantages –

external and internal fragmentation– Paged allocation

Address translation under paged allocation Page table implementation Associative registers, Translation look aside buffers Effective access time calculation Two level paging scheme Inverted page table architecture Sharing pages between processes – adv. Disadv.

– Segmentation-based allocation Address translation under segmentation based

allocation

Silberschatz and Galvin1999 7.4

Chapter 9: Virtual Memory

• What is virtual memory?

• Demand paging (an implementation of virtual memory)– Page faults, effective access time calculation– Page replacement algorithms

FIFO, Optimal algorithm, LRU, Additional reference bit algorithm, Second chance algorithm – comparison of these algorithms

Counting algorithms– LFU (least frequently used )– MFU (most frequently used)

– Allocation of frames Issues that need to be taken into consideration for Different allocation schemes

– Fixed, priority-based, equal, proportionate– Thrashing

What is thrashing? Causes for thrashing Working set model to solve the problem of thrashing How can program structure contribute to thrashing?

Silberschatz and Galvin1999 7.5

Chapter 10: Mass-Storage Structure

• Disk Structure– Cylinders, tracks, sector(block)

• Disk Scheduling– Goal of a good scheduling algorithm– Various scheduling algorithms

FCFS, SSTF, SCAN, C-SCAN, C-LOOK Performance of these algorithms

• Reliability– RAID

• Tertiary storage– Removable disks, WORM disks, Tapes, – Hierarchical storage management

Silberschatz and Galvin1999 7.6

Chapter 11: File System Interface

• File structures

• File attributes, operation, types, access methods

• Device directory

• Different directory structures

– Single level

– Two level

– Tree Structured

– Acyclic graph structured

– General graph structured

• File access protection

Silberschatz and Galvin1999 7.7

Chapter 12: File System Implementation

• File system

– Disk space allocation Contiguous, linked, indirect, Mapping under each allocation UNIX allocation scheme

– Free Space management Bit vector, linked list approach, grouping, counting

Silberschatz and Galvin1999 7.8

Chapter 14 and 15: Protection and Security

• Domain of protection (14.3)

• Access Matrix (14.4 )

• Implementation of access matrix (14.5.1 to 14.5.3)

• The security problem (15.1)

• Program threats: Trojan horse, Trap door, logic bomb, stack and buffer overflow , viruses(15.2)

• System and network threats: worms (15.3.1)

• Cryptography: Asymmetric key cryptosystem, Symmetric key cryptosystem, RSA cryptography, digital signature. (class notes and section 15.4)

Silberschatz and Galvin1999 7.9

Point distribution

• Approximate distribution of points for final exam

– Chapters 3 and 5: processes, synchronization - 25 points

– Chapter 7 : Deadlocks - 15 points

– Chapter 8,9: Main memory, virtual memory : 25 points

– Chapter 10,11, 12: File system, storage: 15 points

– Chapter 14-15 Security, protection : 20 points

(You are allowed to bring in a cheat sheet of size 8 ½ X 11 in.)

Silberschatz and Galvin1999 7.10

Expected Learning Outcome

• Upon successful completion of the course, one would

1. Have understood the various components of the Operating system

2. Understood memory management

3. Understood process management

4. Understood basic mechanisms for protecting computer resources

5. Understood file system management

6. Understood and applied some OS interfaces for application development.