sched/dl/Documentation: Split Section 3

Introduce 4 subsections to make Section 3 more readable.
Signed-off-by: Luca Abeni <luca.abeni@unitn.it>
Signed-off-by: Peter 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.itSigned-off-by: Ingo Molnar <mingo@kernel.org>

Documentation/scheduler/sched-deadline.txt

@@ -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)