From: Luca Abeni Date: Mon, 18 May 2015 13:00:31 +0000 (+0200) Subject: sched/dl/Documentation: Clarify the relationship between tasks' deadlines and absolut... X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=78740858903460d4b926b9a90c705fcb6103da54;p=linux-beck.git 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: Luca Abeni Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner 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: Ingo Molnar --- diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt index 984a01d3c68f..2a924e19912a 100644 --- a/Documentation/scheduler/sched-deadline.txt +++ b/Documentation/scheduler/sched-deadline.txt @@ -249,9 +249,17 @@ CONTENTS the total utilization is smaller or equal than M then the response times of the tasks are limited. - SCHED_DEADLINE can be used to schedule real-time tasks guaranteeing that - the jobs' deadlines of a task are respected. In order to do this, a task - must be scheduled by setting: + Finally, it is important to understand the relationship between the + SCHED_DEADLINE scheduling parameters described in Section 2 (runtime, + 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 - deadline = D