diff options
Diffstat (limited to 'c-user/rate-monotonic/background.rst')
| -rw-r--r-- | c-user/rate-monotonic/background.rst | 15 |
1 files changed, 9 insertions, 6 deletions
diff --git a/c-user/rate-monotonic/background.rst b/c-user/rate-monotonic/background.rst index 9ca7dff..af54591 100644 --- a/c-user/rate-monotonic/background.rst +++ b/c-user/rate-monotonic/background.rst @@ -112,7 +112,9 @@ less than its period. For example, a periodic task's requirements may state that it should execute for 10 milliseconds every 100 milliseconds. Although the execution time may be the average, worst, or best case, the worst-case execution time is more appropriate for use when analyzing system behavior under -transient overload conditions... index:: aperiodic task, definition +transient overload conditions. + +.. index:: aperiodic task, definition In contrast, an aperiodic task executes at irregular intervals and has only a soft deadline. In other words, the deadlines for aperiodic tasks are not @@ -220,8 +222,9 @@ assumptions: - The execution time for each task without preemption or interruption is constant and does not vary. -- Any non-periodic tasks in the system are special. These tasks displace - periodic tasks while executing and do not have hard, critical deadlines. +- Any non-periodic tasks in the system are special. These tasks should not + displace periodic tasks while executing and do not have hard, critical + deadlines. Once the basic schedulability analysis is understood, some of the above assumptions can be relaxed and the side-effects accounted for. @@ -288,9 +291,9 @@ by the Processor Utilization Rule, they can still be guaranteed to meet all their deadlines by application of the First Deadline Rule. This rule can be stated as follows: -For a given set of independent periodic tasks, if each task meets its first -deadline when all tasks are started at the same time, then the deadlines will -always be met for any combination of start times. + For a given set of independent periodic tasks, if each task meets its first + deadline when all tasks are started at the same time, then the + deadlines will always be met for any combination of start times. A key point with this rule is that ALL periodic tasks are assumed to start at the exact same instant in time. Although this assumption may seem to be |