This document provides an overview of UNIX memory management. It discusses the history of UNIX and how it evolved from earlier systems like Multics. It describes swapping as an early technique for virtual memory management in UNIX and how demand paging was later introduced. Key concepts discussed include page tables, page replacement algorithms like two-handed clock, and the kernel memory allocator.
PowerPoint Presentation on Distributed Operating Systems,reasons for opting for distributed systems over centralized systems,types of Distributed Systems,Process Migration and its advantages.
In the given presentation, process overview,process management scheduling typesand some more basic concepts were explained.
Kindly refere the presentation.
Virtual Memory
• Copy-on-Write
• Page Replacement
• Allocation of Frames
• Thrashing
• Operating-System Examples
Background
Page Table When Some PagesAre Not in Main Memory
Steps in Handling a Page Fault
PowerPoint Presentation on Distributed Operating Systems,reasons for opting for distributed systems over centralized systems,types of Distributed Systems,Process Migration and its advantages.
In the given presentation, process overview,process management scheduling typesand some more basic concepts were explained.
Kindly refere the presentation.
Virtual Memory
• Copy-on-Write
• Page Replacement
• Allocation of Frames
• Thrashing
• Operating-System Examples
Background
Page Table When Some PagesAre Not in Main Memory
Steps in Handling a Page Fault
This is the twelfth set of slightly updated slides from a Perl programming course that I held some years ago.
I want to share it with everyone looking for intransitive Perl-knowledge.
A table of content for all presentations can be found at i-can.eu.
The source code for the examples and the presentations in ODP format are on https://github.com/kberov/PerlProgrammingCourse
Threads,
system model,
processor allocation,
scheduling in distributed systems
Load balancing and
sharing approach,
fault tolerance,
Real time distributed systems,
Process migration and related issues
Threads in Operating System | Multithreading | Interprocess CommunicationShivam Mitra
1.Interprocess communication ( IPC )
2. Introduction to threads
3. Difference between threads and process
4. Multiprocessing vs multithreading
5. Multithreading challenges
Unix Process Management
Process management is an integral part of any modern day operating system (OS). The OS must allocate resources to processes, enable processes to share and exchange information, protect the resources of each process from other processes and enable synchronisation among processes
This is the twelfth set of slightly updated slides from a Perl programming course that I held some years ago.
I want to share it with everyone looking for intransitive Perl-knowledge.
A table of content for all presentations can be found at i-can.eu.
The source code for the examples and the presentations in ODP format are on https://github.com/kberov/PerlProgrammingCourse
Threads,
system model,
processor allocation,
scheduling in distributed systems
Load balancing and
sharing approach,
fault tolerance,
Real time distributed systems,
Process migration and related issues
Threads in Operating System | Multithreading | Interprocess CommunicationShivam Mitra
1.Interprocess communication ( IPC )
2. Introduction to threads
3. Difference between threads and process
4. Multiprocessing vs multithreading
5. Multithreading challenges
Unix Process Management
Process management is an integral part of any modern day operating system (OS). The OS must allocate resources to processes, enable processes to share and exchange information, protect the resources of each process from other processes and enable synchronisation among processes
Manta: a new internet-facing object storage facility that features compute by...Hakka Labs
As the amount of unstructured data has greatly exceeded a single computer's ability to process it, data has become increasingly isolated from the compute elements . The resulting haul from stores of record (e.g., SAN, NAS, S3) to transient compute (e.g., Hadoop, EC2) creates needless mechanical work and human labor. Is there a better way? In this talk, we'll explore the coming convergence of data and compute in the cloud, focusing in particular on Joyent's Manta, a new internet-facing object storage facility that features compute. We will describe the design principles for Manta, the engineering challenges in building it, and more generally, the opportunities presented by the convergence of compute and data.
Factored Operating Systems (fos) - The Case for a Scalable Operating System for Multicores - Designing a new operating system targeting manycore
systems with scalability as the primary design constraint,
where space sharing replaces time sharing to increase
scalability.
OpenStack & the Evolving Cloud EcosystemMark Voelker
OpenStack has come a long way since 2010. What started as a collaboration on compute and storage between NASA and Rackspace has changed dramatically and grown into a large, successful open source project that meets the needs of thousands of organizations. But OpenStack hasn’t evolved in a vacuum over the past seven years: the technology landscape around it has been changing as well. Join VMware’s chief OpenStack architect and longtime community member Mark Voelker for a look at the new technology landscape around OpenStack, how we got here, and where we might go next. We’ll discuss how what started as an IaaS platform ending up being a winning platform for Network Functions Virtualization and telco applications, how OpenStack came to be selected as a common underpinning for container orchestration systems like Kubernetes, how OpenStack governance influenced other open source communities, and how OpenStack changed the way companies looked at Open Source. We’ll consider the role IaaS might play in a future that includes options like functions-as-a-service, containers, and the internet of things. We’ll consider OpenStack as a common foundation for a variety of new technologies, and discuss OpenStack’s lasting impact in the cloud ecosystem. We’ll also discuss how OpenStack is changing and adapting to shifts in the technology landscape, both as an open source community and in terms of product offerings. Learn about new interoperability programs targeted at use cases that didn’t exist seven years ago, and new initiatives from the OpenStack technical community and Foundation.
Disk Management through the Computer ManagementAnshGoyal32
Disk Management refers to the process of managing and organizing computer storage devices, such as hard drives and solid-state drives. It involves tasks like creating partitions, formatting drives, assigning drive letters, and managing volumes. Disk Management is a critical aspect of maintaining and optimizing your computer's storage space.
2024.06.01 Introducing a competency framework for languag learning materials ...Sandy Millin
http://sandymillin.wordpress.com/iateflwebinar2024
Published classroom materials form the basis of syllabuses, drive teacher professional development, and have a potentially huge influence on learners, teachers and education systems. All teachers also create their own materials, whether a few sentences on a blackboard, a highly-structured fully-realised online course, or anything in between. Despite this, the knowledge and skills needed to create effective language learning materials are rarely part of teacher training, and are mostly learnt by trial and error.
Knowledge and skills frameworks, generally called competency frameworks, for ELT teachers, trainers and managers have existed for a few years now. However, until I created one for my MA dissertation, there wasn’t one drawing together what we need to know and do to be able to effectively produce language learning materials.
This webinar will introduce you to my framework, highlighting the key competencies I identified from my research. It will also show how anybody involved in language teaching (any language, not just English!), teacher training, managing schools or developing language learning materials can benefit from using the framework.
June 3, 2024 Anti-Semitism Letter Sent to MIT President Kornbluth and MIT Cor...Levi Shapiro
Letter from the Congress of the United States regarding Anti-Semitism sent June 3rd to MIT President Sally Kornbluth, MIT Corp Chair, Mark Gorenberg
Dear Dr. Kornbluth and Mr. Gorenberg,
The US House of Representatives is deeply concerned by ongoing and pervasive acts of antisemitic
harassment and intimidation at the Massachusetts Institute of Technology (MIT). Failing to act decisively to ensure a safe learning environment for all students would be a grave dereliction of your responsibilities as President of MIT and Chair of the MIT Corporation.
This Congress will not stand idly by and allow an environment hostile to Jewish students to persist. The House believes that your institution is in violation of Title VI of the Civil Rights Act, and the inability or
unwillingness to rectify this violation through action requires accountability.
Postsecondary education is a unique opportunity for students to learn and have their ideas and beliefs challenged. However, universities receiving hundreds of millions of federal funds annually have denied
students that opportunity and have been hijacked to become venues for the promotion of terrorism, antisemitic harassment and intimidation, unlawful encampments, and in some cases, assaults and riots.
The House of Representatives will not countenance the use of federal funds to indoctrinate students into hateful, antisemitic, anti-American supporters of terrorism. Investigations into campus antisemitism by the Committee on Education and the Workforce and the Committee on Ways and Means have been expanded into a Congress-wide probe across all relevant jurisdictions to address this national crisis. The undersigned Committees will conduct oversight into the use of federal funds at MIT and its learning environment under authorities granted to each Committee.
• The Committee on Education and the Workforce has been investigating your institution since December 7, 2023. The Committee has broad jurisdiction over postsecondary education, including its compliance with Title VI of the Civil Rights Act, campus safety concerns over disruptions to the learning environment, and the awarding of federal student aid under the Higher Education Act.
• The Committee on Oversight and Accountability is investigating the sources of funding and other support flowing to groups espousing pro-Hamas propaganda and engaged in antisemitic harassment and intimidation of students. The Committee on Oversight and Accountability is the principal oversight committee of the US House of Representatives and has broad authority to investigate “any matter” at “any time” under House Rule X.
• The Committee on Ways and Means has been investigating several universities since November 15, 2023, when the Committee held a hearing entitled From Ivory Towers to Dark Corners: Investigating the Nexus Between Antisemitism, Tax-Exempt Universities, and Terror Financing. The Committee followed the hearing with letters to those institutions on January 10, 202
Operation “Blue Star” is the only event in the history of Independent India where the state went into war with its own people. Even after about 40 years it is not clear if it was culmination of states anger over people of the region, a political game of power or start of dictatorial chapter in the democratic setup.
The people of Punjab felt alienated from main stream due to denial of their just demands during a long democratic struggle since independence. As it happen all over the word, it led to militant struggle with great loss of lives of military, police and civilian personnel. Killing of Indira Gandhi and massacre of innocent Sikhs in Delhi and other India cities was also associated with this movement.
Read| The latest issue of The Challenger is here! We are thrilled to announce that our school paper has qualified for the NATIONAL SCHOOLS PRESS CONFERENCE (NSPC) 2024. Thank you for your unwavering support and trust. Dive into the stories that made us stand out!
Francesca Gottschalk - How can education support child empowerment.pptxEduSkills OECD
Francesca Gottschalk from the OECD’s Centre for Educational Research and Innovation presents at the Ask an Expert Webinar: How can education support child empowerment?
A Strategic Approach: GenAI in EducationPeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
How to Make a Field invisible in Odoo 17Celine George
It is possible to hide or invisible some fields in odoo. Commonly using “invisible” attribute in the field definition to invisible the fields. This slide will show how to make a field invisible in odoo 17.
Embracing GenAI - A Strategic ImperativePeter Windle
Artificial Intelligence (AI) technologies such as Generative AI, Image Generators and Large Language Models have had a dramatic impact on teaching, learning and assessment over the past 18 months. The most immediate threat AI posed was to Academic Integrity with Higher Education Institutes (HEIs) focusing their efforts on combating the use of GenAI in assessment. Guidelines were developed for staff and students, policies put in place too. Innovative educators have forged paths in the use of Generative AI for teaching, learning and assessments leading to pockets of transformation springing up across HEIs, often with little or no top-down guidance, support or direction.
This Gasta posits a strategic approach to integrating AI into HEIs to prepare staff, students and the curriculum for an evolving world and workplace. We will highlight the advantages of working with these technologies beyond the realm of teaching, learning and assessment by considering prompt engineering skills, industry impact, curriculum changes, and the need for staff upskilling. In contrast, not engaging strategically with Generative AI poses risks, including falling behind peers, missed opportunities and failing to ensure our graduates remain employable. The rapid evolution of AI technologies necessitates a proactive and strategic approach if we are to remain relevant.
3. Introduction
UNIX is a portable, multi-tasking and multi-user operating
system.
– Portable: runs on many different hardware architectures (Intel
x86 and IA-64, Alpha, MIPS, HP PA-RISC, PowerPC, IBM
S/390, SPARC, Motorola 680x0, etc.).
– Preemptive multi-tasking: several programs can run at the
same time (time slices, interrupts, and task switching).
– Multi-user: many users can share the computer system at the
same time.
3
4. Other Features…
• Uses a simple, uniform file model which includes devices and
access to other services in a flexible, hierarchical file system.
• Written in a high-level language (“C”) making it easy to
read, understand, change and port.
• The command prompt is a simple user process, the Unix shell,
which is also a convenient job programming language.
• Includes support for regular expressions which are convenient
for complex searching.
4
5. History of UNIX
• 1964 joint project between AT&T Bell Labs, GE, and MIT to
develop a new OS.
• Goal : develop an OS that could provide computational
power, data storage and the ability to share data among
multiple users.
• Result: Multiplexed Information & Computer Service -
MULTICS.
5
6. • 1969 Bell Labs withdraws from group.
• Two Bell Lab scientists, Ken Thompson and Dennis Ritchie,
continue research. They were still left without a “Convenient
interactive computing service”*.
• At the same time Ken Thompson wrote a game “space
travel” in Fortran to run on GECOS OS.
• The spaceship was hard to control and it was expensive to
run. He was told to get the game off his work computer.
6
7. • Thompson ported the game to a little used PDP-7 computer.
• Unics (later Unix) was born as a pun on Multics.
• Dennis Ritchie developed “B” . Then wrote “C” a compiled
language.
• In 1973 entire OS ported to “C”.
• 1991 Linux 0.02 is first released to the public.
• 1994 Linux 1.0 is released.
7
8. Memory Management
UNIX is machine independent so its memory management
scheme will vary from one system to next.
Early versions of UNIX used variable partitioning with no
virtual memory scheme.
Current implementations of UNIX make use of paged virtual
memory.
There are two memory management schemes :
Paging System
Kernal Memory Allocator
8
10. Memory Management policies
• Swapping
– Easy to implement
– Less system overhead
• Demand Paging
– Greater Flexibility
10
11. Swapping
• The process of moving some pages out of main memory and
moving others in, is called swapping.
• A page fault occurs when the CPU tries to access a page that
is not in main memory, thus forcing the CPU to wait for the
page to be swapped in.
• Since moving data to and from disks takes a significant
amount of time, the goal of the memory manager is to
minimize the number of page faults.
11
12. • Swap Space - Disk memory used to hold data that is not in
Real or File System memory. Swap space is most efficient
when it is on a separate disk or partition, but sometimes it is
just a large file in the File System.
• Allocation of both main memory and swap space is done
first-fit.
• A page fault occurs when the CPU tries to access a page
that is not in main memory, thus forcing the CPU to wait for
the page to be swapped in.
12
13. • Since moving data to and from disks takes a significant
amount of time, the goal of the memory manager is to
minimize the number of page faults.
• When the size of a process' memory image increases (due to
either stack expansion or data expansion), a new piece of
memory big enough for the whole image is allocated.
• If no single piece of main memory is large enough, the
process is swapped out such that it will be swapped back in
with the new size.
13
14. • Decisions regarding which processes to swap in or swap out
are made by the scheduler process (also known as the
swapper).
• A process is more likely to be swapped out if it is idle or has
been in main memory for a long time, or is large ; if no
obvious candidates are found, other processes are picked by
age.
• A process is more likely to be swapped in if its has been
swapped out a long time, or is small.
14
16. Allocating Swap Space
Address Unit
Allocate 100 unit
1 10000 101 9900
Map
Allocate 50 unit
Allocate 100 unit
251 9850 151 9750
16
17. Freeing Swap Space
Address Unit
50 unit free at 101
251 9750 101 50
Map 251 9750
Case 1: Free resources fill a hole,
but not contiguous to any resources in the map
17
18. Freeing Swap Space
Address Unit
50 unit free at 101 101 50
251 9750
251 9750
Map
100 unit free at 1
1 150
Case 2: Free resources fill a hole,
251 9750
and immediately precedes an entry in the map
18
19. Freeing Swap Space
Address Unit 101 50
50 unit free at 101
251 9750 251 9750
Map
100 unit free at 1
1 150 Allocate 200 unit 1 150
451 9550 251 9750
300 unit free at 151 Case 3: Free resources fill a
hole, and completely fills the
1 10000 gap between entries in the
map 19
20. Demand Paging
• Demand paging to unix with BSD(Berkley system) which
transferred memory pages instead of process to and from a
secondary device.
• When a process needs a page and the page is not there, a
page fault to the kernel occurs a frame of main memory is
allocated, and the process is loaded into the frame by the
kernel.
20
21. Page Table
Page Frame Age Copy on Modify Reference Valid Protect
Number write
• frame # contains the physical frame where the virtual page
is stored
• age is processor dependant, and is meant to maintain how
long it has been since the page was accessed.
• Copy on Write store the copy on write bit, which is used in
UNIX systems to, among other things, render fork efficient.
21
22. • Dirty is a single bit that indicates whether a page has been
modified since last swapped in (the opposite of dirty is clean,
and a clean page need not be written out to disk if
swapped).
• Ref contains the usage information necessary for a CLOCK-
style algorithm.
• Valid is the standard UNIX jargon for resident. A valid page
is in main memory, an invalid one is swapped out.
• Protect contains the permission information for the page
and is also hardware dependant.
22
23. Disk block descriptor
Swap device Number Device Block No. Type of storage
• The disk block descriptor contains the information mapping
a virtual page to a spot on disk.
• The OS maintains a table of descriptors for each process.
23
24. • Device # is basically a pointer to the disk that this page was
swapped to.
• Block # is the actual block that the page is stored on. This is
why most UNIX systems prefer to have a separate swap
partition, so that the block size can be set to the page size.
• Type specifies whether the page is new or pre-existing. This
lets the OS know if it has to clear the frame first.
24
25. Page frame data table
Page State Reference Logical Block Pf data
Count device number pointer
• The page frame data table holds information about each
physical frame of memory (indexed by frame number).
• This table is of primary importance for the replacement
algorithm.
25
26. • Page state indicates whether or not the frame is available or
has an associated page (i.e. whether its been allocated to a
process or not).
• Ref. Count holds the number of processes that refer to this
page (remember, processes can share the same physical
page).
• Logical device contains the device number of the disk that
holds a physical copy of the page.
26
27. • Block # holds the block number on that disk where the
page data is located.
• Pfdata pointer is a pointer field that is used to thread a
singly-linked list of free frames through the frame table. If
the page is free, this points to the next free page (useful for
free list-style allocation).
27
28. Swap use table
Reference Page/storage
count unit number
• Reference Count : Number of page table entries that point
to a page on the swap device.
• Page/storage unit number : Page identifier on storage unit
28
29. Page Replacement Algorithm
• The Page frame data table is used for page replacement.
• All of the available frames are linked together in a list of free
frames available for bringing in pages.
• The two-handed clock algorithm uses the reference bit in the
page table entry for each page in memory that is eligible
(not locked) to be swapped out.
• This bit is set to 0 when when the page is first brought in and
set to 1 when the page is refernced for a read or write .
29
31. • Two parameters determine the operation of the algorithm:
– Scanrate: The rate at which the two hands scan through the
page list, in pages per second.
– Handspread: The gap between fronthand and backhand
• These two parameters have default values set at boot time
based on the amount of physical memory.
31
32. • The parameter varies linearly between the values slowscan
and fastscan as the amount of free memory varies between
the values lotsfree and minfree.
• The handspread parameter determines the gap between the
fronthand and the backhand and therefore, together with
scanrate,determines the window of oppurtunity to use a
page before it is swapped out due to lack of use.
32
33. Kernal Memory Allocator
• Kernel memory allocator: provides buffers of memory to
various kernel subsytems.
Evolution Criteria :
– must be space-efficient i.e. minimize wastage.
– Can be measured by utilization factor
– must be fast
– must have a simple programming interface
– should not force to free the entire allocated area all at once
– must guard against the wastage of memory
– must be able to interact with the paging system
33
34. Advantages
• easy to implement
• not restricted to memory allocation
• no wastage of space
• can release any part of the region
• allows reuse of memory by coalescing
34
35. References
Books :
*********
1. Os Internals & design
--- William Stallings
2. The design of the unix operating system
--- Maurice J. Bach prentice hall
35