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Commit 6aaa1025 authored by Luca Abeni's avatar Luca Abeni Committed by Ingo Molnar
Browse files

sched/dl/Documentation: Split Section 3 



Introduce 4 subsections to make Section 3 more readable.

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/1431954032-16473-10-git-send-email-luca.abeni@unitn.it


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 78740858

Documentation/scheduler/sched-deadline.txt

+16 −0
Original line number Diff line number Diff line
@@ -8,6 +8,10 @@ CONTENTS 
 1. Overview

 2. Scheduling algorithm

 3. Scheduling Real-Time Tasks

   3.1 Definitions

   3.2 Schedulability Analysis for Uniprocessor Systems

   3.3 Schedulability Analysis for Multiprocessor Systems

   3.4 Relationship with SCHED_DEADLINE Parameters

 4. Bandwidth management

   4.1 System-wide settings

   4.2 Task interface
@@ -126,6 +130,9 @@ CONTENTS 
 suited for periodic or sporadic real-time tasks that need guarantees on their

 timing behavior, e.g., multimedia, streaming, control applications, etc.



3.1 Definitions

------------------------



 A typical real-time task is composed of a repetition of computation phases

 (task instances, or jobs) which are activated on a periodic or sporadic

 fashion.
@@ -166,6 +173,9 @@ CONTENTS 
 is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum

 utilization[12].



3.2 Schedulability Analysis for Uniprocessor Systems

------------------------



 If M=1 (uniprocessor system), or in case of partitioned scheduling (each

 real-time task is statically assigned to one and only one CPU), it is

 possible to formally check if all the deadlines are respected.
@@ -204,6 +214,9 @@ CONTENTS 
 time-consuming to be performed on-line. Hence, as explained in Section

 4 Linux uses an admission test based on the tasks' utilizations.



3.3 Schedulability Analysis for Multiprocessor Systems

------------------------



 On multiprocessor systems with global EDF scheduling (non partitioned

 systems), a sufficient test for schedulability can not be based on the

 utilizations or densities: it can be shown that even if D_i = P_i task
@@ -249,6 +262,9 @@ CONTENTS 
 the total utilization is smaller or equal than M then the response times of

 the tasks are limited.



3.4 Relationship with SCHED_DEADLINE Parameters

------------------------



 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)