OS-CO1-Session 03 Resource Management

Operating Systems
Resource Management
Department of Artificial Intelligence and Data Science

Koneru Lakshmaiah Education Foundation
(Deemed to be University)
Green fields, Vaddeswaram, AP-522502, India
Session : 3
Resource Management
• Process Management
• Memory Management
• File-system Management
• Mass-Storage Management
• Caching
• Characteristics of Various Types of Storage
• Migration of data “A” from Disk to Register
• I/O Subsystem
• Protection and Security
• Virtualization
• Kernel Data Structures
13/07/2022 Operating Systems - CO1 2
Process Management
• A process is a program in execution. It is a unit of work within the
system. Program is a passive entity; process is an active entity.
• Process needs resources to accomplish its task
• CPU, memory, I/O, files
• Initialization data
• Process termination requires reclaim of any reusable resources
• Single-threaded process has one program counter specifying location
of next instruction to execute
• Process executes instructions sequentially, one at a time, until completion
• Multi-threaded process has one program counter per thread
• Typically system has many processes, some user, some operating
system running concurrently on one or more CPUs
• Concurrency by multiplexing the CPUs among the processes / threads
Process Management Activities
The operating system is responsible for the following

activities in connection with process management:
• Creating and deleting both user and system processes

• Suspending and resuming processes
• Providing mechanisms for process synchronization
• Providing mechanisms for process communication
• Providing mechanisms for deadlock handling

Memory Management
• To execute a program all (or part) of the instructions must be in
memory
• All (or part) of the data that is needed by the program must be in
memory
• Memory management determines what is in memory and when
• Optimizing CPU utilization and computer response to users
• Memory management activities
• Keeping track of which parts of memory are currently being used and by
whom
• Deciding which processes (or parts thereof) and data to move into and out
of memory
• Allocating and deallocating memory space as needed

File-system Management
• OS provides uniform, logical view of information storage
• Abstracts physical properties to logical storage unit - file
• Each medium is controlled by device (i.e., disk drive, tape drive)
• Varying properties include access speed, capacity, data-transfer rate,
access method (sequential or random)
• File-System management
• Files usually organized into directories
• Access control on most systems to determine who can access what
• OS activities include
• Creating and deleting files and directories
• Primitives to manipulate files and directories
• Mapping files onto secondary storage
• Backup files onto stable (non-volatile) storage media
Mass-Storage Management
• Usually disks used to store data that does not fit in main memory
or data that must be kept for a “long” period of time
• Proper management is of central importance
• Entire speed of computer operation hinges on disk subsystem
and its algorithms
• OS activities
• Mounting and unmounting
• Free-space management
• Storage allocation
• Disk scheduling
• Partitioning
• Protection
Caching
• Important principle, performed at many levels in a computer
(in hardware, operating system, software)
• Information in use copied from slower to faster storage
temporarily
• Faster storage (cache) checked first to determine if information
is there
• If it is, information used directly from the cache (fast)
• If not, data copied to cache and used there
• Cache smaller than storage being cached
• Cache management important design problem
• Cache size and replacement policy

Characteristics of Various Types of
Storage
Movement between levels of storage hierarchy can be explicit or implicit

Migration of data “A” from Disk to
Register
• Multitasking environments must be careful to use most
recent value, no matter where it is stored in the storage
hierarchy
Multiprocessor environment must provide cache coherency

in hardware such that all CPUs have the most recent value in
their cache
• Distributed environment situation even more complex
• Several copies of a datum can exist
I/O Subsystem
• One purpose of OS is to hide peculiarities of hardware
devices from the user
• I/O subsystem responsible for
• Memory management of I/O including buffering (storing
data temporarily while it is being transferred), caching
(storing parts of data in faster storage for performance),
spooling (the overlapping of output of one job with input
of other jobs)
• General device-driver interface
• Drivers for specific hardware devices
Protection and Security
• Protection – any mechanism for controlling access of processes or
users to resources defined by the OS
• Security – defense of the system against internal and external attacks
• Huge range, including denial-of-service, worms, viruses, identity theft, theft of
service
• Systems generally first distinguish among users, to determine who can
do what
• User identities (user IDs, security IDs) include name and associated number,
one per user
• User ID then associated with all files, processes of that user to determine
access control
• Group identifier (group ID) allows set of users to be defined and controls
managed, then also associated with each process, file
• Privilege escalation allows user to change to effective ID with more rights
Virtualization
• Allows operating systems to run applications within other OSes
• Vast and growing industry
• Emulation used when source CPU type different from target
type (i.e. PowerPC to Intel x86)
• Generally slowest method
• When computer language not compiled to native code –
Interpretation
• Virtualization – OS natively compiled for CPU, running guest
OSes also natively compiled
• Consider VMware running WinXP guests, each running applications,
all on native WinXP host OS
• VMM (virtual machine Manager) provides virtualization services
Virtualization (cont.)
• Use cases involve laptops and desktops running multiple OSes

for exploration or compatibility
• Apple laptop running Mac OS X host, Windows as a guest
• Developing apps for multiple OSes without having multiple systems
• Quality assurance testing applications without having multiple
systems
• Executing and managing compute environments within data centers
• VMM can run natively, in which case they are also the host
• There is no general-purpose host then (VMware ESX and Citrix
XenServer)

Kernel Data Structures
• Many similar to standard programming data structures
• Singly linked list
• Doubly linked list
• Circular linked list

• Binary search tree
left <= right
• Search performance is O(n)
• Balanced binary search tree is O(lg n)

• Hash function can create a hash map
• Bitmap – string of n binary digits representing the status of n

items
• Linux data structures defined in include files
<linux/list.h>, <linux/kfifo.h>,
<linux/rbtree.h>
Resource Management
Process Management
Memory Management
File-system Management
Mass-Storage Management
Caching
Characteristics of Various Types of Storage
Migration of data “A” from Disk to Register
I/O Subsystem
Protection and Security
Virtualization
Kernel Data Structures

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Operating Systems

Department of Artificial Intelligence and Data Science

The operating system is responsible for the following

• Creating and deleting both user and system processes

13/07/2022 Operating Systems - CO1 4

13/07/2022 Operating Systems - CO1 5

13/07/2022 Operating Systems - CO1 8

Movement between levels of storage hierarchy can be explicit or implicit

13/07/2022 Operating Systems - CO1 9

Multiprocessor environment must provide cache coherency

• Use cases involve laptops and desktops running multiple OSes

13/07/2022 Operating Systems - CO1 14

• Doubly linked list

• Circular linked list

13/07/2022 Operating Systems - CO1 15

13/07/2022 Operating Systems - CO1 16

• Bitmap – string of n binary digits representing the status of n

13/07/2022 Operating Systems - CO1 18

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