Flashcards
Sistemas Operativos
Cards in this deck (76)
- 1What is an Operating System?A program that acts as an intermediary between a user of a computer and the computer hardware
- 2Computer system can be divided into four components:Hardware
Operating System
Application programs
Users - 3The one program running at all times on the computer” is the kernel. Everything else is eitherA system program (ships with the operating system) , or
an application program. - 4What is caching?copying information into faster storage system; main memory can be viewed as a cache for secondary storage
- 5Storage-Device Hierarchy
- 6Asymmetric Multiprocessingeach processor is assigned a specie task.
- 7Symmetric Multiprocessingeach processor performs all tasks
- 8features of Clustered SystemsUsually sharing storage via a storage-area network (SAN)
Provides a high-availability service which survives failures
Asymmetric clustering has one machine in hot-standby mode
Symmetric clustering has multiple nodes running applications, monitoring each other
Some clusters are for high-performance computing (HPC)
Some have distributed lock manager (DLM) to avoid conflicting operations - 9Multiprogramming (Batch system)Needed for efficiency
Single user cannot keep CPU and I/O devices busy at all times
Multiprogramming organizes jobs (code and data) so CPU always has one to execute
One job selected and run via job scheduling - 10Timesharing (multitasking)is logical extension in which CPU switches jobs so frequently that users can interact with each job while it is running, creating interactive computing
Response time should be < 1 second
If processes don’t fit in memory, swapping moves them in and out to run
If several jobs ready to run at the same time → CPU scheduling - 11Mode bitProvided by hardware
Provides ability to distinguish when system is running user code or kernel code
Some instructions designated as privileged, only executable in kernel mode - 12What is a process?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.
- 13Responabilities of the operative SystemCreating 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 - 14Memory Management activitiesKeeping 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 - 15Storage ManagementCreating and deleting files and directories
Primitives to manipulate files and directories
Mapping files onto secondary storage
Backup files onto stable (non-volatile) storage media - 16I/O Subsystem responsabilitiesMemory 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 - 17Network is a communications path, TCP/IP most common:Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
Personal Area Network (PAN) - 18What is P2PPeer to Peer
P2P does not distinguish clients and servers
Instead all nodes are considered peers
May each act as client, server or both
Node must join P2P network - 19One set of operating-system services provides functions that are helpful to the user:
- 20What is CLICommand Line Interface
Windows: command
Apple: Aqua
Linux: CDE,KDE,GNOME - 21Three comon APIsWin32 API for Windows
POSIX API for POSIX-based systems (including virtually all versions of UNIX, Linux, and Mac OS X)
Java API for the Java virtual machine (JVM) - 22Methods used to pass parameters to the OSSimplest: pass the parameters in registers
Parameters stored in a block, or table, in memory, and address of block passed as a parameter in a register
Parameters placed, or pushed, onto the stack by the program and popped off the stack by the operating system - 23What is fork() used for?Shell executes fork() system call to create process
- 24What is exec() used for?Shell executes exec() to load program into process
- 25System programs provide a convenient environment for program development and execution. They can be divided into:File manipulation
Status information sometimes stored in a File modification
Programming language support
Program loading and execution
Communications
Background services
Application programs - 26User goals and System goalsUser goals – operating system should be convenient to use, easy to learn, reliable, safe, and fast
System goals – operating system should be easy to design, implement, and maintain, as well as flexible, reliable, error-free, and efficient - 27What is a System Call?They are mechanism whereby a program ask to the SO for low level tasks, also known as privileged tasks.
An API is a set of functions that facilitate to the programmers doing applications, covering the low level tasks and giving them a made up interface. - 28Policiy and MechanismMechanism determine how to do something
Policies determine what will be done. - 29What is a linker?Source files are compiled into object files that are designed to be loaded into any physical memory location, a format known as an relocatable object fil . Next, the linker combines these relocatable object files into a single binary executable file.
- 30What is a Loader?A loader is used to load the binary executable file into memory, Operative Systems often load the libraries at the same time they are loading the program in order not to link and load libraries that may end up not being used.
- 31Simple Operative System StructureMonolithic Structure
The simplest structure for organizing an operating system is no structure at all. That is, place all of the functionality of the kernel into a single, static binary file that runs in a single address space. - 32Layered Approach System StructureThe operating system is divided into a number of layers (levels), each built on top of lower layers. The bottom layer (layer 0), is the hardware; the highest (layer N) is the user interface.
- 33MicrokernelIt consists in separate some of the kernel´s functions, putting them in the user mode in order to make the kernel compact and smaller.
Its principal issue is the communication among services, since the OS has to switch from one process to the next to exchange the messages. - 34ModulesThe best current methodology for operating-system design involves using loadable kernel modules (LKMs). Here, the kernel has a set of core components and can link in additional services via modules, either at boot time or during run time.
- 35What is a Core Dump and a Crash DumpCore Dump: A capture of the memory of the process
Crash Dump: A capture of the memory of the kenel - 36What is a CrashAn error in kernel's runtime, the information about the error is saved in a log file
- 37Parts of a processThe program code, also called text section
Current activity including program counter, processor registers
Stack containing temporary data
Function parameters, return addresses, local variables
Data section containing global variables
Heap containing memory dynamically allocated during run time - 38Diagram of Process State
- 39What is PCBInformation associated with each process
(also called task control block)
Process state – running, waiting, etc
Program counter – location of instruction to next execute
CPU registers – contents of all process-centric registers
CPU scheduling information- priorities, scheduling queue pointers
Memory-management information – memory allocated to the process
Accounting information – CPU used, clock time elapsed since start, time limits
I/O status information – I/O devices allocated to process, list of open files - 40Scheduling queues (3)Job queue – set of all processes in the system
Ready queue – set of all processes residing in main memory, ready and waiting to execute
Device queues – set of processes waiting for an I/O device - 41Short-term schedulerCPU scheduler
Short-term scheduler is invoked frequently (milliseconds) (must be fast) - 42Long-term scheduler(job scheduler) – selects which processes should be brought into the ready queue
Long-term scheduler is invoked infrequently (seconds, minutes) (may be slow) - 43(1)I/O-bound process (2)CPU-bound process(1)more I/O than CPU
(2)More CPU than I/O - 44SwappingRemove process from memory, store on disk, bring back in from disk to continue execution
- 45Context SwitchWhen CPU switches to another process, the system must save the state of the old process and load the saved state for the new process via a context switch
- 46Parent and childrenThey form a tree of processes identified dentified and managed via a process identifier (pid)
- 47Process terminationReturns status data from child to parent (via wait())
Process’ resources are deallocated by operating system - 48cascading termination.All children, grandchildren, etc. are terminated.
- 491) Zombie Process 2)Orphan Process1) No parent waiting
2) Parent terminated without invoking wait() - 50(1)Independent Processes (2)Cooperating ProcessesIndependent process cannot affect or be affected by the execution of another process
Cooperating process can affect or be affected by the execution of another process
(1) need Interprocess Communication (IPC)
Two models of IPC:
Shared memory
Message passing - 51send() receive()send (P, message) – send a message to process P
receive(Q, message) – receive a message from process Q
all of this through a link, directed and received from PORTS (mailbox) - 52Synchronization (1)Blocking (2)Non-Blocking(1)synchronous
Blocking send
Blocking receive
(2)asynchronous
Non-Blocking send
Non-Blocking receive - 53Three ways of implementing buffering1. Zero capacity – no messages are queued on a link. Sender must wait for receiver (rendezvous)
2. Bounded capacity – finite length of n messages. Sender must wait if link full
3. Unbounded capacity – infinite length Sender never waits - 54Communication between server and client
- 55SocketA socket is defined as an endpoint for communication
Concatenation of IP address and port – a number included at start of message packet to differentiate network services on a host - 56RPCRemote procedure call (RPC) abstracts procedure calls between processes on networked systems
- 57Pipes and Named PipesActs as a conduit allowing two processes to communicate
Named Pipes are more powerful than ordinary pipes
Communication is bidirectional
No parent-child relationship is necessary between the communicating processes - 58MultithreadingResponsiveness – may allow continued execution if part of process is blocked, especially important for user interfaces
Resource Sharing – threads share resources of process, easier than shared memory or message passing
Economy – cheaper than process creation, thread switching lower overhead than context switching
Scalability – process can take advantage of multicore architectures - 59(1)Parallelism (2)Concurrency(1)implies a system can perform more than one task simultaneously
(2) supports more than one task making progress
Single processor / core, scheduler providing concurrency - 60Data and Task Parallelism
- 61Multithreading ModelsMany-to-One
One-to-One
Many-to-Many
(User Thread → Kernel Thread) - 62Categories of system calls
- 63Implicit ThreadingFive methods explored
Thread Pools
Fork-Join
OpenMP
Grand Central Dispatch
Intel Threading Building Blocks - 64Thread PoolsCreate a number of threads in a pool where they await work
- 65Fork-Join ParallelismMultiple threads (tasks) are forked, and then joined.
- 66OpenMpIdentifies parallel regions – blocks of code that can run in parallel
- 67Grand Central DispatchAllows identification of parallel sections of code, then it puts into blocks.
Blocks placed in dispatch queue
Assigned to available thread in thread pool when removed from queue - 68Intel Threading Building Blocks (TBB)Template library for designing parallel C++ programs
- 69Signal and signal handlingsSignals are used in UNIX systems to notify a process that a particular event has occurred.
A signal handler is used to process signals
Signal is generated by particular event
Signal is delivered to a process
Signal is handled by one of two signal handlers:
default
user-defined - 70Thread CancellationThread to be canceled is target thread
Two general approaches:
Asynchronous cancellation terminates the target thread immediately
Deferred cancellation allows the target thread to periodically check if it should be cancelled - 71Scheduler ActivationsTypically use an intermediate data structure between user and kernel threads – lightweight process (LWP)
Appears to be a virtual processor on which process can schedule user thread to run
Each LWP attached to kernel thread - 72Context of threadThe register set, stacks, and private storage area are known as the context of the thread
- 73Threads Data Structures
- 74Critical Section ProblemEach process has critical section segment of code
Process may be changing common variables, updating table, writing file, etc
When one process in critical section, no other may be in its critical section - 75Synchronization HardwareMany systems provide hardware support for implementing the critical section code.
All solutions based on idea of locking
Protecting critical regions via locks - 76Mutex LockProtect a critical section by first acquire() a lock then release() the lock
Boolean variable indicating if lock is available or not
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- Flashcards on Sistemas Operativos, created by Enderson Gonzalo Diaz Munoz on 29/09/2018.
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- Enderson Gonzalo Diaz Munoz
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