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COE128 > COE 186 > Flashcards

COE 186 Flashcards

1
Q

Is the maximum time within which it must complete its execution

A

Deadline

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2
Q

A real-time task is said to be _____ if producing the result after its deadline may cause catastrophic consequences on the system under control.

A

hard

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3
Q

Areal-time task is said to be ______ if producing the results after its deadline is useless for the system, but does not cause any damage.

A

firm

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4
Q

A real-time task is said to be _____ if producing the results after its deadline has still some utility for the system, although causing a performance degradation.

A

soft

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5
Q

A real-time operating system that is able to handle hard real-time tasks

A

hard real-time system

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6
Q

Very important basic properties that real-time systems must have to support critical applications.

A
  • Timeliness
  • Predictability
  • Efficiency
  • Robustness
  • Fault tolerance
  • Maintainability
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7
Q

Is a technique used by many peripheral devices to transfer data between the device and the main memory

A

Direct memory access (DMA)

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8
Q

Is a fast memory that is inserted as a buffer between the CPU and the random-access memory (RAM) to speed up processes’ execution.

A

Cache

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9
Q

It occurs when a high-priority task is blocked by a low-priority task for an unbounded interval of time

A

Priority inversion

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10
Q

is a computation that is executed by the CPU in a sequential fashion

A

process

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11
Q

The operation of suspending the running task and inserting it into the ready queue

A

preemption

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12
Q

A __________ is an assignment of tasks to the processor, so that each task is executed until completion.

A

Schedule

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13
Q

A schedule is said to be _________ if all tasks can be completed according to a set of specified constraints.

A

feasible

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14
Q

A set of tasks is said to be _________ if there exists at least one algorithm that can produce a feasible schedule

A

schedulable

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15
Q

is the time at which a task becomes ready for execution; it is also referred to as request time or release time and indicated by rᵢ

A

Arrival time aᵢ

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16
Q

is the time necessary to the processor for executing the task without interruption

A

Computation time Cᵢ

17
Q

is the time before which a task should be completed to avoid damage to the system

A

Absolute Deadline dᵢ

18
Q

is the difference between the absolute deadline and the request time

A

Relative Deadline Dᵢ

19
Q

is the time at which a task starts its execution

A

Start time sᵢ

20
Q

is the time at which a task finishes its execution

A

Finishing time fᵢ

21
Q

is the difference between the finishing time and the request time

A

Response time Rᵢ

22
Q

is a parameter related to the consequences of missing the deadline (typically, it can be hard, firm, or soft).

A

Criticality

23
Q

represents the relative importance of the task with respect to the other tasks in the system

A

Value vᵢ

24
Q

represents the delay of a task completion with respect to its deadline; note that if a task completes before the deadline, its lateness is negative

A

Lateness Lᵢ

25
Q

Relative Deadline formula

A

Dᵢ = dᵢ - rᵢ

26
Q

Response time formula

A

Rᵢ = fᵢ - rᵢ

27
Q

Lateness formula

A

Lᵢ = fᵢ - dᵢ

28
Q

is the time a task stays active after its deadline

A

Tardiness or Exceeding time Eᵢ

29
Q

is the maximum time a task can be delayed on its activation to complete within its deadline

A

Laxity or Slack time Xᵢ

30
Q

Laxity or Slack time formula

A

Xᵢ = dᵢ - aᵢ - Cᵢ

31
Q

consist of an infinite sequence of identical activities, called instances or jobs, which are regularly activated at a constant rate

A

Periodic tasks

32
Q

consist of an infinite sequence of identical jobs (or instances); however, their activations are not regularly interleaved

A

Aperiodic tasks

33
Q

The activation time of the first periodic instance (τi,1)

A

phase

34
Q

is a situation in which two or more tasks are blocked indefinitely because
each task is waiting for a resource acquired by another blocked task.

A

Deadlock

35
Q

is a scheduling algorithm which assigns
dynamic priorities to tasks according to their absolute deadlines: the task with the
shortest deadline is assigned the highest priority

A

Earliest deadline first (EDF) algorithm

36
Q

is the variation of end-to-end transfer delay (i.e., the
difference between the maximum and minimum values of transfer delay)

A

Jitter of packet (or delay jitter)

37
Q

it is the minimum interval of time after which the schedule repeats itself. If H is the length of such an interval, then the schedule in [0,H) is the same as that in [kH, (k + 1)H], for any integer k > 0

A

Hyperperiod

38
Q

is priority level associated with a semaphore or a resource according to an access protocol.

A

Ceiling

39
Q

is a kernel data structure used to synchronize the execution of concur-rent jobs.

A

Semaphore

COE128 (7 decks)

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