Swap space management and protection in os

swap space management

1. SWAP SPACE MANAGEMENT AND PROTECTION 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 3 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 S ubject Access control polices Object S ource 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