Section 1
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graceful degradation
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Section 1
(50 cards)
graceful degradation
The ability to continue providing service proportional to the level of surviving hardware is called
middleware
a set of software frameworks that provide additional services to application developers. supports databases, multimedia, and graphics (to name only a few).
application programs
define the ways in which hardware resources are used to solve users' computing problems
How does software signal an interrupt?
executing a special operation called a system call (also called a monitor call).
user's view
varies according to the interface being used.
What are three main advantages of Multiprocessor systems?
1. Increased throughput. 2. Economy of scale. 3. Increased reliability
Increased reliability
If functions can be distributed properly among several processors, then the failure of one processor will not halt the system, only slow it down.
operating system
a program that manages a computer's hardware. It also provides a basis for application programs and acts as an intermediary between the computer user and the computer hardware.
How is the occurrence of an event signaled
by an interrupt from either the hardware or the software.
device driver
understands the device controller and provides the rest of the operating system with a uniform interface to the device.
How does hardware signal an interrupt?
by sending a signal to the CPU, usually by way of the system bus.
Where is the bootstrap program stored
within the computer hardware in read-only memory (ROM) or electrically erasable programmable read-only memory (EEPROM), known by the general term firmware.
System View
computer's point of view, the operating system is the program most intimately involved with the hardware. In this context, we can view an operating system as a resource allocator.
direct memory access (DMA)
After setting up buffers, pointers, and counters for the I/O device, the device controller transfers an entire block of data directly to or from its own buffer storage to memory, with no intervention by the CPU. one interrupt is generated per block, much faster than sending one interrupt per byte
system daemons
programs that run the entire time the kernel is running.
small computer-systems interface (SCSI) controller
I/O device , seven or more devices can be attached
What are two other names for a multiprocessor system?
parallel systems multicore system
What is the goal of a user view for a user that is sitting in front of a PC?
ease of use, with some attention paid to performance and none paid to resource utilization optimized for the single-user experience
What does the bootstrap program load
The Kernel
device controller
responsible for moving the data between the peripheral devices that it controls and its local buffer storage
store instruction
moves the content of a register to main memory.
control program
manages the execution of user programs to prevent errors and improper use of the computer. It is especially concerned with the operation and control of I/O devices.
What are four components that a computer system can be divided into?
hardware, operating system, application programs, users
asymmetric multiprocessing
in which each processor is assigned a specific task. A boss processor controls the system; the other processors either look to the boss for instruction or have predefined tasks.
What is the hierarchy of storage relating to speed?
registers cache main memory solid state disk hard disk optical disk magnetic tapes
What is the method for handling interrupts quickly?
only a predefined number of interrupts is possible, a table of pointers to interrupt routines can be used instead to provide the necessary speed. table is na array
Where do general purpose computers run programs from?
re-writable memory called main memory (also called random-access memory, or RAM).
volatile storage device that loses its contents when power is turned off or otherwise lost.
volatile storage device that loses its contents when power is turned off or otherwise lost.. Main memory is volatile storage
Switch architecture
one interrupt is generated per block
In addition to the kernel, what are the two other types of programs?
system programs, which are associated with the operating system but are not necessarily part of the kernel application programs, which include all programs not associated with the operation of the system.
What is the goal of a user view for a users that sit at workstations connected to networks of other workstations and servers.
operating system is designed to compromise between individual usability and resource utilization.
Uniform Memory Access (UMA)
the situation in which access to any RAM from any CPU takes the same amount of time
Economy of scale.
can cost less than equivalent multiple single-processor systems,
Hardware
central processing unit (CPU), memory, input/output (I/O) devices —provides the basic computing resources for the system
fault tolerant
can suffer a failure of any single component and still continue operation
secondary storage as an extension of main memory. The main requirement for secondary storage is that it be able to hold large quantities of data permanently.
an extension of main memory. The main requirement for secondary storage is that it be able to hold large quantities of data permanently.
What is the most common secondary storage device for both programs and data?
hard disk drive (HDD)
Increased throughput
The speed-up ratio with N processors is not N, however; rather, it is less than N
What is another name for an operating system?
Kernel
How is symmetric and asymmetric multiprocessing achieved
may result from either hardware or software
bootstrap program
when a computer is powered up or rebooted—it needs to have an initial program to run. This initial program, or bootstrap program
symmetric multiprocessing (SMP)
most common each processor performs all tasks, including operating system functions and user processes. SMP means that all processors are peers; no boss-worker relationship exists between processors.
load instruction
moves a byte or word from main memory to an internal register within the CPU
What semiconductor technology is used for RAM?
dynamic random-access memory (DRAM).
Moore's Law
predicted that the number of transistors on an integrated circuit would double every eighteen months, and that prediction has held true
What is the benefit of having an integrated memory controller with mutliple CPUs?
can increase the amount of memory addressable in the system
What are examples of computers that have little or no user view?
embedded computers in home devices and automobiles may have numeric keypads and may turn indicator lights on or off to show status, but they and their operating systems are designed primarily to run without user intervention.
What is the goal of a user view for a user that is sitting in front of a mainframe or a minicomputer
operating system isdesigned to maximize resource utilization—to assure that all available CPU time, memory, and I/O are used efficiently and that no individual user takes more than her fair share.
system processes
system programs that are loaded into memory at boot time
NVRAM
DRAM with battery backup power. This memory can be as fast as DRAM and (as long as the battery lasts) is nonvolatile.
Section 2
(50 cards)
CPU scheduling,
if several jobs are ready to run at the same time, the system must choose which job will run first.
How does the central procssor read and write data on a von Nuemann architecture?
reads instructions from main memory during the instruction-fetch cycle and both reads and writes data from main memory during the data-fetch cycle
tertiary storage devices
Magnetic tape drives and their tapes and CD and DVD drives and platters
cache
Information is normally kept in some storage system (such as main memory). As it is used, it is copied into a faster storage system on a temporary basis.
symmetric clustering
two or more hosts are running applications and are monitoring each other. This structure is obviously more efficient, as it uses all of the available hardware. However it does require that more than one application be available to run.
job pool
main memory is too small to accommodate all jobs, the jobs are kept initially on the disk This pool consists of all processes residing on disk awaiting allocation of main memory.
What do parallel clusters allow for?
clustering over a wide-area network (WAN). allow multiple hosts to access the same data on shared storage.
blade servers
relatively recent development in which multiple processor boards, I/O boards, and networking boards are placed in the same chassis. The difference between these and traditional multiprocessor systems is that each blade-processor board boots independently and runs its own operating system. Some blade-server boards are multiprocessor as well,
distributed lock manager (DLM)
included in some cluster technology, provides access control and locking when multiple computers data on the same data on shared storage. to ensure that no conflicting operations occur. This function, commonly known as a
What does windows call user identifiers (user IDs)
security ID (SID)
Why is clustering used?
to provide high-availability service—that is, service will continue even if one or more systems in the cluster fail.
What type of computing environment can clusters provide
high-performance computing environments.
BEOWULF CLUSTERS
designed to solve high-performance computing tasks. consists of commodity hardware—such as personal computers—connected via a simple local-area network. No single specific software package is required to construct a cluster. Rather, the nodes use a set of open-source software libraries to communicate with one another
clustered system
which gathers together multiple CPUs. Clustered systems differ from the multiprocessor systems described in Section 1.3.2 in that they are composed of two or more individual systems—or nodes—joined together. Such systems are considered loosely coupled. share storage and are closely linked via a local-area network LAN or a faster interconnect, such as InfiniBand.
What is required of the response time for an interactive computer system?
should be short—typically less than one second.
Multiprogramming
ability of operating system to run more than one program at once. increases CPU utilization by organizing jobs (code and data) so that the CPU always has one to execute.
interrupt driven
. If there are no processes to execute, no I/O devices to service, and no users to whom to respond, an operating system will sit quietly, waiting for something to happen.
Time sharing (or multitasking)
is a logical extension of multiprogramming. In time-sharing systems, the CPU executes multiple jobs by switching among them, but the switches occur so frequently that the users can interact with each program while it is running.
kernel mode.
whenever the operating system gains control of the computer,
What activities is the operating system responsible for in connection with file management?
Creating and deleting files Creating and deleting directories to organize files Supporting primitives for manipulating files and directories Mapping files onto secondary storage Backing up files on stable (nonvolatile) storage media
what does an operating system do?
An operating system provides the environment within which programs are executed.
virtual memory
a technique that allows the execution of a process that is not completely in memory Helps ensure reasonable response time.
array
a simple data structure in which each element can be accessed directly. For example, main memory is constructed as an array.
What happens when a virtual machine manager(VMM) is in control of the system?
has more privileges than user processes but fewer than the kernel.
asymmetric clustering.
one machine is in hot-standby mode while the other is running the applications. The hot-standby host machine does nothing but monitor the active server. If that server fails, the hot-standby host becomes the active server
WORM
write-once, read-many-times storage
What activities is the operating system responsible for in connection with memory management?(3)
Keeping track of which parts of memory are currently being used and who is using them Deciding which processes (or parts of processes) and data to move into and out of memory Allocating and deallocating memory space as needed
Protection
any mechanism for controlling the access of processes or users to the resources defined by a computer system. This mechanism must provide means to specify the controls to be imposed and to enforce the controls.
What type of operating system does a Beowulf cluster usually run?
Linux operating system
parallelization,
application must have been written specifically to take advantage of the cluster, divides a program into separate components that run in parallel on individual cores in a computer or computers in a cluster.
RW
read-write storage
interactive computer system
which provides direct communication between the user and the system
What are some examples of privileged instructions
The instruction to switch to kernel mode I/O control, timer management, interrupt management.
timer
ensure that the operating system maintains control over the CPU. We cannot allow a user program to get stuck in an infinite loop or to fail to call system services and never return control to the operating system A timer can be set to interrupt the computer after a specified period. The period may be fixed (for example, 1/60 second) or variable (for example, from 1 millisecond to 1 second).
swapping
processes are swapped in and out of main memory to the disk. Helps ensure reasonable response time.
What activities is the operating system responsible for in connection with disk management?
Free-space management Storage allocation Disk scheduling
What is an important benefit of SANs?
If the host fails, then any other host can take over.
privileged instructions
designation some of the machine instructions that may cause harm as If an attempt is made to execute a privileged instruction in user mode, the hardware does not execute the instruction but rather treats it as illegal and traps it to the operating system.
What is added to hardware to indicate whether an operating system is in Kernel mod or user mode?
the mode bit, is added to the hardware of the computer to indicate the current mode: kernel (0) or user (1).
file
a logical storage unit The operating system maps files onto physical media and accesses these files via the storage devices.
What is the main advantage of virtual memory?
it enables users to run programs that are larger than actual physical memory. Further, it abstracts main memory into a large, uniform array of storage, separating logical memory as viewed by the user from physical memory. This arrangement frees programmers from concern over memory-storage limitations.
non-uniform memory access (NUMA).
some parts of memory may take longer to access than other parts, creating a performance penalty. Operating systems can minimize the NUMA penalty through resource management
process
A program loaded into memory
I/O subsystem
A memory-management component that includes buffering, caching, and spooling A general device-driver interface Drivers for specific hardware devices
What is used to implement group functionality (user groups with certain permissions)
group identifiers.
list
represents a collection of data values as a sequence. The most common method for implementing this structure is a linked list, in which items are linked to one another.
job scheduling
Time sharing and multiprogramming require that several jobs be kept simultaneously in memory. If several jobs are ready to be brought into memory, and if there is not enough room for all of them, then the system must choose among them.
storage-area networks (SANs)
allow many systems to attach to a pool of storage. If the applications and their data are stored on the SAN, then the cluster software can assign the application to run on any host that is attached to the SAN.
What activities is the operating system responsible for in connection with process management?(5)
Scheduling processes and threads on the CPUs Creating and deleting both user and system processes Suspending and resuming processes Providing mechanisms for process synchronization Providing mechanisms for process communication
trap (or an exception)
a software-generated interrupt caused either by an error (for example, division by zero or invalid memory access) or by a specific request from a user program that an operating-system service be performed
Section 3
(48 cards)