CSCI 447 Operating Systems Filip Jagodzinski

Transcription

1 Filip Jagodzinski

2 Announcements Homework 1 An extension of Lab 1 Big picture : for Homework 1 and 2, we ll focus on the lowlevel mechanics of the OS. Per the instructions, create a new branch in your gitlab for homework1, and submit your code to the branch for grading Submission of your answers to the book questions is via Canvas. Reminders Do the recommended readings The lecture slides complement and not supplement the recommended readings

3 Announcements Homework 1, Program Demo make blitz g afunprog

4 Review Multiprogramming : goal : increases CPU utilization by ensuring that the CPU has always something to execute (code to run) Several jobs are kept in memory Memory Hierarchy not all jobs can be in memory at one time OS picks one of the jobs in memory to execute When a job is waiting for an I/O operation, the OS switches to another job 0 max OS Job 1 Job 2 Job 3 Job 4 Job 5

5 Review Multiprogramming : goal : increases CPU utilization by ensuring that the CPU has always something to execute (code to run) Several jobs are kept in memory 0 max OS Job 1 Job 2 Job 3 Job 4 Job 5 Memory Hierarchy not all jobs can be in memory at one time OS picks one of the jobs in memory to execute When a job is waiting for an I/O operation, the OS switches to another job Issues that we want to be aware of : Job scheduling & synchronization & fair use of resources (timer -> interrupt) Swapping/Virtual memory Security

6 Review (programs/software) GUI batch user interface Command line system calls services (hardware)

7 Review (programs/software) Program Execution : load program into memory and run it I/O operations : send data to screen, send data to speaker, send data to/from a file GUI batch user interface system calls Command line File systems : create a file, delete a file, add to a file, etc. Communications : via shared memory or via message (packet) passing Services for the user services Error detection : should be able to detect and effectively response to any type of error (hardware)

8 Review (programs/software) Resource allocation Scheduling algorithms Accounting Which user/process uses how much of a specific resource GUI batch user interface system calls Command line time, space, fair access to a shared resource Protection and security In a multiuser system one user/process might not want to make available its data to another (Skype and Firefox running concurrently) Services for the user Services for efficient system operation services (hardware)

9 Review (programs/software) mkdir mydir When a command line instruction is issued the command must be interpreted Two approaches GUI Command batch line user interface system calls 1. The command interpreter itself can execute the command services (hardware)

10 Review (programs/software) mkdir mydir When a command line instruction is issued the command must be interpreted Two approaches GUI Command batch line user interface system calls 1. The command interpreter itself can execute the command 2. The command interpreter has no knowledge of what the command does, but instead launches a system program services (hardware)

11 In-class exercise

12 Today Finish Chapter 2 Begin Chapter 3

13 Operating System Structures program argument (programs/software) mkdir mydir When a command line instruction is issued the command must be interpreted Most operating systems include a command interpreter that has no knowledge of what the command does, but instead launches a system program Q: Where are these programs located? Multiple locations, including /usr/include/x86_64-linux-gnu/sys/ (demo which.h file contains mkdir?) GUI batch user interface system calls services (hardware) Command line

14 Operating System Structures Q: How are parameters passed to the OS? (programs/software) GUI batch user interface Command line system calls services (hardware)

15 Operating System Structures Q: How are parameters passed to the OS? 1. Pass parameter via registers (programs/software) GUI batch user interface Command line system calls (1) param register services user process (2) (3) Operating system (hardware)

16 Operating System Structures Q: How are parameters passed to the OS? 1. Pass parameter via registers Q: What are the limitations of this approach? (programs/software) GUI batch user interface system calls Command line (1) param register services user process (2) (3) Operating system (hardware)

17 Operating System Structures Q: How are parameters passed to the OS? 1. Pass parameter via registers 2. Save parameters in block or table (in memory), and pass via the registers the address of the block (programs/software) GUI batch user interface system calls Command line services register user process Operating system (hardware)

18 Operating System Structures Q: How are parameters passed to the OS? 1. Pass parameter via registers 2. Save parameters in block or table (in memory), and pass via the registers the address of the block Q: What are the advantages of this approach? (1) table address (programs/software) GUI batch user interface system calls services Command line register user process (2) (3) Operating system (hardware)

19 Operating System Structures Q: How are parameters passed to the OS? 1. Pass parameter via registers 2. Save parameters in block or table (in memory), and pass via the registers the address of the block 3. Placed (pushed) onto the stack (programs/software) GUI batch user interface system calls Command line services register user process Operating system (hardware)

20 Operating System Structures System Calls Several basic types (programs/software) GUI batch Command line user interface system calls services (hardware)

21 Operating System Structures System Calls Several basic types 1. Process Control end, abort, load, create process, Need to halt, normally or via abort 2. File Management create file, delete file, open file, Manage files and directories (programs/software) GUI batch user interface system calls Command line services (hardware)

22 Operating System Structures System Calls Several basic types 1. Process Control end, abort, load, create process, Need to halt, normally or via abort 2. File Management create file, delete file, open file, Manage files and directories 3. Device Management request device, write to device, Process might need multiple resources 4. Information Management get process attributes, set system data, get time or date, Keep track of up-time and waiting (programs/software) GUI batch user interface system calls services Command line (hardware)

23 Operating System Structures System Calls Several basic types 1. Process Control end, abort, load, create process, Need to halt, normally or via abort 2. File Management create file, delete file, open file, Manage files and directories 3. Device Management request device, write to device, Process might need multiple resources 4. Information Management get process attributes, set system data, get time or date, Keep track of up-time and waiting 5. Communications create connection, send message, transfer status information Message passing and shared memory 6. Protection prevent read, allow modification by owner only Manipulate protections of resources (programs/software) GUI batch user interface system calls services (hardware) Command line

24 Processes Chapter 3

25 Processes Early computers, with limited resources, and no multiprocessing Load the entire program into memory, and run Shared and/or Multiprocessor Computers Multiple programs running at the same time

26 Processes Early computers, with limited resources, and no multiprocessing Load the entire program into memory, and run Drawbacks/Advantages Shared and/or Multiprocessor Computers Multiple programs running at the same time Drawbacks/Advantages

27 Processes Early computers, with limited resources, and no multiprocessing Load the entire program into memory, and run Drawbacks/Advantages Shared and/or Multiprocessor Computers Multiple programs running at the same time Drawbacks/Advantages Only 1 program running at any one time No sharing of resources No security protocols Program in control of all architecture elements Shared CPUs Concurrent processes One program shouldn t see or interfere with other programs

28 Processes Q: What is a process?

29 Processes Q: What is a process? Process : a program in execution Q: What a

30 Processes Q: What is a process? Process : a program in execution Q: What are all of the required elements/components needed to run and/or schedule a job? Analogy : think of a manager of a store/company what info/details are needed so that the manager can schedule employee shifts? Q: What a

31 Processes Q: What is a process? Process : a program in execution But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: The program file (executable program), aka the text section The current activity currently executing, which includes the value of the program counter (PC in first lecture), Q: What and a the value(s) of the registers The memory image text, data, heap, stack

32 Processes Q: What is a process? Process : a program in execution But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: The program file (executable program), aka the text section The activity currently executing, which includes the value of the program counter (PC in first lecture), and the value(s) of the registers The memory image text, data, heap, stack

33 A process in memory Processes Q: What is a process? Process : a program in execution stack But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: The program file (executable program), aka the text section The activity currently executing, which includes the value of the program counter (PC in first lecture), and the value(s) of the registers The memory image text, data, heap, stack heap data text Q: What is the distinction between the heap and the stack?

34 A process in memory Processes Q: What is a process? Process : a program in execution stack But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: heap The program file (executable program), aka the text section The activity currently executing, which includes the value of the program counter (PC in first lecture), and the value(s) of the registers The memory image text, data, heap, stack data text Q: What is the distinction between the heap and the stack? Dynamically allocated No pattern for use (difficult to manage) Temporary data LIFO (easy(ish) to manage)

35 Processes Q: What is a process? Process : a program in execution But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: The program file (executable program), aka the text section The activity currently executing, which includes the value of the program counter (PC in first lecture), and the value(s) of the registers Process state The memory image text, data, heap, stack Q: In the context of today s multiprocessor computers, what are the possible states of a process? Hint : there are 5 of them White board brainstorm Caveats : only 1 process can be running on any processor at any instance, while many processes may be ready and waiting

36 Processes Q: What is a process? Process : a program in execution But it is more than just the program at the architecture and OS levels of abstraction, a job consists of: The program file (executable program), aka the text section The activity currently executing, which includes the value of the program counter (PC in first lecture), and the value(s) of the registers Process state The memory image text, data, heap, stack New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) Ready : process is waiting to be assigned a processor Terminated : finished executing Caveats : only 1 process can be running on any processor at any instance, while many processes may be ready and waiting

37 Processes Q: What transition pathways are possible for a process during non-error operation? For example, can a process transition from new to terminated? From waiting to running? From terminated to ready? Analogy : can an employee go form Terminated to New? New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) Ready : process is waiting to be assigned a processor Terminated : finished executing

38 Processes Q: What transition pathways are possible for a process during non-error operation? For example, can a process transition from new to terminated? From waiting to running? From terminated to ready? New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) new running Ready : process is waiting to be assigned a processor Terminated : finished executing ready waiting terminated

39 Processes Task : Be able to list an example of an activity that a process undergoes to force any of the transitions. Q: For example, what event might cause a process to transition from a running state to a waiting state? Q: What determines that transition from ready to running? new running New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) Ready : process is waiting to be assigned a processor Terminated : finished executing ready waiting terminated

40 Processes Q: Why would we not want the OS to implement a transition option from New to Running? New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) new running Ready : process is waiting to be assigned a processor Terminated : finished executing ready waiting terminated

41 Processes But the state of a process is not enough to permit the OS to manage the process, nor all of the processes Task : Assume you are the OS and you need to schedule/manage multiple processes what information do you need about each process? White board brainstorm New : being created Running : being executed Waiting : for some event to occur (usually I/O operation) Ready : process is waiting to be assigned a processor Terminated : finished executing

42 Processes Process Control Block : a repository for information about processes

43 Processes Process Control Block : a repository for information about processes One of a several current states State

44 Processes Process Control Block : a repository for information about processes One of a several current states Recall the intro lecture What does PC refer to? And what is its utility? State

45 Processes Process Control Block : a repository for information about processes One of a several current states Address of next instruction for process State Program Counter

46 Processes Process Control Block : a repository for information about processes One of a several current states Address of next instruction for process Depending on the architecture, the type and count of specific registers varies regardless, it is their content that is important State Program Counter CPU Registers

47 Processes Process Control Block : a repository for information about processes One of a several current states Address of next instruction for process Depending on the architecture, the type and count of specific registers varies regardless, it is their content that is important Process priority, pointers to scheduling queues, etc. State Program Counter CPU Registers CPU Scheduling Info

48 Processes Process Control Block : a repository for information about processes One of a several current states Address of next instruction for process Depending on the architecture, the type and count of specific registers varies regardless, it is their content that is important Process priority, pointers to scheduling queues, etc. Page tables, segment tables, etc. Amount of CPU already used, time limits, job or process number List of I/O devices allocated to/in use by process, list of open files, etc. State Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status

49 Processes Process Control Block : a repository for information about processes What is the PCB used for? How does an OS utilize it? State Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status

50 Processes Process Control Block : a repository for information about processes What is the PCB used for? How does an OS utilize it? The insight is that the PCB for each process explains fully the details of the process its instructions, the state of the data on-chip, what I/O devices the process needs This enables the OS to save a snapshot of a process, file that snapshot away in the case that the process is idle (waiting), and swap in (switch to) another process State Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status

51 Processes Process Control Block : a repository for information about processes Process 0 OS

52 Processes Process Control Block : a repository for information about processes Interrupt System call Process 0 save OS PCB_0 Q: What type of interrupt/system call might trigger this type of behavior? Enumerate three possibilities.

53 Processes Process Control Block : a repository for information about processes Process 0 save OS Process 1 Interrupt System call PCB_0 PCB_1 (re)load time

54 Processes Process Control Block : a repository for information about processes Process 0 save OS Process 1 Interrupt System call PCB_0 PCB_1 (re)load time save Interrupt System call Q: What type of interrupt/system call might trigger this type of behavior? Enumerate three possibilities.

55 Processes Process Control Block : a repository for information about processes Process 0 save OS Process 1 Interrupt System call PCB_0 PCB_1 (re)load time save Interrupt System call Assuming Process 0 has transitioned from waiting to ready, AND is scheduled by the OS to be the next process to resume execution what happens next?

56 reload Processes Process Control Block : a repository for information about processes Process 0 save OS Process 1 Interrupt System call PCB_0 PCB_1 (re)load time resume save Interrupt System call

57 Processes Scheduling Before we can discuss algorithms for scheduling CPU usage we need a system in place for keeping tack of which process wants/needs to use which resource. Q: what data structure(s) would you use, and why? A. Heap B. Queue C. Stack D. BST

58 Processes Scheduling Ready queue head tail Q: What are the individual elements of the queue?

59 Processes Scheduling PCB_24 State Ready queue head tail Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status

60 Processes Scheduling PCB_24 State Q: What does this refer to? Ready queue head tail Program Counter CPU Registers CPU Scheduling Info Memory Management Info Q: How many elements/items are in this queue? Accounting Info I/O status

61 Processes Scheduling PCB_24 Ready queue head tail State Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status PCB_7 State Program Counter CPU Registers CPU Scheduling Info Memory Management Info Accounting Info I/O status

62 Up Next Chapter 3, Scheduling