This document discusses various topics related to memory management in computer systems: 1. It defines deadlock and describes the four necessary conditions for deadlock to occur. 2. It explains different approaches for deadlock prevention, detection, avoidance and recovery. 3. It describes swapping as a memory management technique where processes can be moved between main and secondary memory. 4. It discusses contiguous memory allocation and fixed-size and variable-size partitioning schemes for allocating memory to processes.

1. DEADLOC
K
NEIL FERDINAND B. EDER | BS COMPUTER
ENGINEERING

2. 01 02 03
04
System Model
TABLE OF CONTENTS
Deadlock
Characterization
Deadlock
Prevention,
Detection, &
Avoidance
Recovery from deadlock
banker’s algorithm

3. 05 06 07
08 09 10
Swapping
TABLE OF CONTENTS
Contiguous
Allocation of
frames
Thrashing
Paging
Page
Memory
Allocation
replacement
algorithms

4. 11
Case Study
TABLE OF CONTENTS

5. 01
System Model

6. System
Model
A system is an organized group of
related objects or components;
models can be used for
understanding and predicting
the behavior of systems.

7. 02
Deadlock Characterization

8. Deadlock
It is a situation where a set of processes are
blocked because each process is holding a
resource and waiting for another resource
acquired by some other process.

9. Example of Deadlock

10. Necessary Conditions
1. Mutual Exclusion 3. No preemption
2. Hold and Wait 4. Circular Wait

11. Mutual
Exclusion
Only one process can use a resource
at any given time i.e. the resources
are non-sharable.

12. Hold and
Wait
A process is holding at least one
resource at a time and is waiting
to acquire other resources held
by some other process.

13. No Preemption
The resource can be released by a
process voluntarily i.e. after execution
of the process

14. Circular
Wait
A set of processes are waiting for
each other in a circular fashion

15. 03
Prevention, Detection & Avoidance

16. Deadlock Prevention, Detection, & Avoidance, and Recovery.
Prevention- This is done by restraining the ways a request can
be made. Since deadlock occurs when all the
above four conditions are met, we try to prevent
any one of them, thus preventing a deadlock.
Detection & Avoidance- We let the system fall into a
deadlock and if it happens, we detect it using a
detection algorithm and try to recover.
When a process requests a resource, the
deadlock avoidance algorithm examines the
resource-allocation state. If allocating that resource
sends the system into an unsafe state, the request is got
granted.

17. 04
Recovery

18. 04
Recovery

19. Deadlock Prevention, Detection, & Avoidance, and Recovery.
Therefore, it requires additional information such as
how many resources of each type is required by a
process. If the system enters into an unsafe state, it has to take a
step back to avoid deadlock.
Recovery- Some ways of recovery are as follows.
○ Aborting all the deadlocked processes.
○ Abort one process at a time until the system recovers from the
deadlock.
○ Resource Preemption: Resources are taken one by one from a
process and assigned to higher priority processes until the
deadlock is resolved.

20. Memory
Manageme
nt

21. 05
Swapping

22. Swapping
● Swapping is a memory management scheme in which any process can be
temporarily swapped from main memory to secondary memory so that the main
memory can be made available for other processes. It is used to improve main
memory utilization. In secondary memory, the place where the swapped-out
process is stored is called swap space.

23. Swap-out
Swap-out is a method of removing a process from RAM and adding it to the hard
disk.
Swap-in is a method of removing a program from a hard disk and putting it back into
the main memory or RAM.
Types of Swapping
Swap-in

24. 06
Contiguous Memory Allocation

25. Contiguous Memory Allocation
● Contiguous memory allocation refers to a memory management technique in
which whenever there occurs a request by a user process for the memory, one
of the sections of the contiguous memory block would be given to that process,
in accordance with its requirement.

26. Fixed-size Partition
Scheme
This scheme is also known as Dynamic partitioning and iThis technique is also
known as Static partitioning. In this scheme, the system divides the memory into
fixed-size partitions. The partitions may or may not be the same size. The size of
each partition is fixed as indicated by the name of the technique and it cannot be
changed.
This scheme is also known as Dynamic partitioning and is came into existence to
overcome the drawback i.e internal fragmentation that is caused by Static
partitioning. In this partitioning, scheme allocation is done dynamically.
Contiguous memory management techniques
Variable-size Partition Scheme

27. Fixed-size
Partition
Schem
e

28. Fixed-size Partition
Schem
e

29. Variable-size Partition
Schem
e

30. Paging
● Paging is a storage mechanism used to retrieve processes from the secondary
storage into the main memory in the form of pages.