swap space management

1. Submitted by,
D.SHANMUGAPRIYA
I-MSC(IT)
NADAR SARASWATHI COLLEGE OF ARTS
AND SCIENCE

2. INTRODUCTION
 Is the second time of memory in modern linux systems.
 Swap Space:-virtual memory uses disk space as an
extension of main memory.
 Main goal for the design and implementation of swap
space is to provide the best throughput for VM system.
 Swap space use swapping use swap space to hold entire
process image.
 Some OS may support multiple swap space.

3. SWAP SPACE LOCATION
 Swap space can be carved out of the normal file system
or in a separate disk partition
 Catching block location information in main memory.
 Contiguous allocation for the swap file.
 But the cost of traversing is data structure still
remains.

4. DATA STRUCTURE FOR SWAPPING
ON LINK SYSTEMS
SWAP AREA
PAGE SLOT
Swap file
Swap map
1 0 3 0 1

5. WHY SWAP SPACE
 When the amount of physical memory is full and the system
need more memory resources for new process then system
may get show or collapse .
 To make RAM more efficient as compare to present state.
 EXAMPLE : Swap space equal 2xphysical RAM for up to
2GB of physical RAM and then an additional 1x physical
RAM for any amount above 2GB.
 M=amount of RAM in GB.
 S=Amount of swap in GB.
If m<2
S=m*2
Else
S=m+2

6. PROTECTION
 INTRODUCTION
 GOALS OF PROTECTION
 PRINCIPLES OF PROTECTION
 ACCESS CONTROL
 BASIC TERMINOLOGY
 DOMAIN
 IMPLEMENTATION

7. INTRODUCTION
 Protection refers to a mechanism for controlling the
access of programs processes or used to the resources
defined by a computer system.
 Protection ensures that the resources of the computer
are used in a proper way.
 It ensure that each object accessed correctly and only
by those process that are allowed to do so.

8. GOALS OF PROTECTION
 We need to provide protection for several reasons.
 The most obvious is the need to prevent the bad ,
intentional violation of an access restriction by user.
 A role of protection in a computer system is to provide
a mechanism for the implementation of the polices
governing resource use
 A protection system must have the flexibility to enforce
a variety of policies.

9. PRINCIPLES OF PROTECTION
 The time tested guiding principle for protections the
principle of least privilege.
 It dictates the programs users and even system be
given enough privileges to perform their tasks.
 The principles of least privilege can help produce a
more secure computing environment.

10. ACCESS CONTROL
 Is concerned with determining the allows activities of
valid users , mediating every attempt by a user to
access a resource in the system.
Access request
Subject
Access
control
polices
Objec
t
Source Guard Resources

11. BASIC TERMINOLOGY
 OBJECT:- Access to an object potentially implies
access to the information it contains.
 [e .g] file ,program , printer.
 ACCESS RIGHTS:-The permission granted to a user
to perform an operation .
 [e .g] Read , write , execute.

12. DOMAIN
 Collection of object and a set of access right for each of
the object.
 A process operates within a protection domain that
specifies the resources that the process may access.
<obj1(read , write)
<obj2(read , write)
<obj3(execute)

13. ACCESS CONTROL MATRIX
 View protection as a matrix
 Rows represent domains
 Columns represent object
 Each entry in the matrix consists of a set of access
rights.

14. Cont….
DOMAIN
/OBJECT
F1 F2 F3 PRINTER
D1 Read Read
D2 Point
D3 Read Execute
D4 Read
write
Read
write

15. IMPLEMENTATION
 Each column=Access control list for one object defines
who can perform what operation
Domain 1=Read ,write
Domain 2=Read
Domain 3=Read
Each Row=capability list
object 1=Read
object 4=Read , write , execute
object 5=Read , write , delete , copy