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Commit 78740858 authored by Luca Abeni's avatar Luca Abeni Committed by Ingo Molnar
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sched/dl/Documentation: Clarify the relationship between tasks' deadlines and... 


sched/dl/Documentation: Clarify the relationship between tasks' deadlines and absolute scheduling deadlines

Clarify what is the relationship between tasks' parameters and scheduling
parameters, explaining how to set the scheduling parameters so that all the
absolute deadlines of a task are respected.

Signed-off-by: default avatarLuca Abeni <luca.abeni@unitn.it>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: henrik@austad.us
Cc: juri.lelli@gmail.com
Cc: raistlin@linux.it
Link: http://lkml.kernel.org/r/1431954032-16473-9-git-send-email-luca.abeni@unitn.it


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 134136c4

Documentation/scheduler/sched-deadline.txt

+11 −3
Original line number Original line Diff line number Diff line
@@ -249,9 +249,17 @@ CONTENTS 
 the total utilization is smaller or equal than M then the response times of

 the total utilization is smaller or equal than M then the response times of

 the tasks are limited.

 the tasks are limited.





 SCHED_DEADLINE can be used to schedule real-time tasks guaranteeing that

 Finally, it is important to understand the relationship between the

 the jobs' deadlines of a task are respected. In order to do this, a task

 SCHED_DEADLINE scheduling parameters described in Section 2 (runtime,

 must be scheduled by setting:

 deadline and period) and the real-time task parameters (WCET, D, P)

 described in this section. Note that the tasks' temporal constraints are

 represented by its absolute deadlines d_j = r_j + D described above, while

 SCHED_DEADLINE schedules the tasks according to scheduling deadlines (see

 Section 2).

 If an admission test is used to guarantee that the scheduling deadlines

 are respected, then SCHED_DEADLINE can be used to schedule real-time tasks

 guaranteeing that all the jobs' deadlines of a task are respected.

 In order to do this, a task must be scheduled by setting:





  - runtime >= WCET

  - runtime >= WCET

  - deadline = D

  - deadline = D