Hardware Reference
In-Depth Information
Buffer
A memory area shared by two or more tasks for exchanging data.
Capacity
The maximum amount of time dedicated by a periodic server, in each
period, to the execution of a service.
Ceiling
Priority level associated with a semaphore or a resource according to an
access protocol.
Ceiling blocking
A special form of blocking introduced by the Priority Ceiling Pro-
tocol.
Channel
A logical link through which two or more tasks exchange information by
a message-passing mechanism.
Chained blocking
A sequence of blocking experienced by a task while attempting
to access a set of shared resources.
Clairvoyance
An ideal property of a scheduling algorithm that implies the future
knowledge of the arrival times of all the tasks that are to be scheduled.
Competitive factor
A scheduling algorithm
A
is said to have a competitive factor
ϕ
A
if and only if it can guarantee a cumulative value at least
ϕ
A
times the cumula-
tive value achieved by the optimal clairvoyant scheduler.
Completion time
The time at which a job finishes executing. It is also called
finish-
ing time
.
Computation time
The amount of time required by the processor to execute a job
without interruption. It is also called
service time
or
processing time
.
Concurrent processes
Processes that overlap in time.
Context
A set of data that describes the state of the processor at a particular time,
during the execution of a task. Typically the context of a task is the set of values
taken by the processor registers at a particular instant.
Context switch
A kernel operation consisting in the suspension of the currently
executing job for assigning the processor to another ready job (typically the one
with the highest priority).
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