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authorLuca Abeni <luca.abeni@unitn.it>2015-05-18 09:00:32 -0400
committerIngo Molnar <mingo@kernel.org>2015-05-19 02:39:21 -0400
commit6aaa10254dfe61c8c5e87c26e21be0664782a5b4 (patch)
tree3a93ef074b6da8977ace24c00dd7533a979d3c6b /Documentation/scheduler
parent78740858903460d4b926b9a90c705fcb6103da54 (diff)
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.it Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'Documentation/scheduler')
-rw-r--r--Documentation/scheduler/sched-deadline.txt16
1 files changed, 16 insertions, 0 deletions
diff --git a/Documentation/scheduler/sched-deadline.txt b/Documentation/scheduler/sched-deadline.txt
index 2a924e19912a..e114513a2731 100644
--- a/Documentation/scheduler/sched-deadline.txt
+++ b/Documentation/scheduler/sched-deadline.txt
@@ -8,6 +8,10 @@ CONTENTS
8 1. Overview 8 1. Overview
9 2. Scheduling algorithm 9 2. Scheduling algorithm
10 3. Scheduling Real-Time Tasks 10 3. Scheduling Real-Time Tasks
11 3.1 Definitions
12 3.2 Schedulability Analysis for Uniprocessor Systems
13 3.3 Schedulability Analysis for Multiprocessor Systems
14 3.4 Relationship with SCHED_DEADLINE Parameters
11 4. Bandwidth management 15 4. Bandwidth management
12 4.1 System-wide settings 16 4.1 System-wide settings
13 4.2 Task interface 17 4.2 Task interface
@@ -126,6 +130,9 @@ CONTENTS
126 suited for periodic or sporadic real-time tasks that need guarantees on their 130 suited for periodic or sporadic real-time tasks that need guarantees on their
127 timing behavior, e.g., multimedia, streaming, control applications, etc. 131 timing behavior, e.g., multimedia, streaming, control applications, etc.
128 132
1333.1 Definitions
134------------------------
135
129 A typical real-time task is composed of a repetition of computation phases 136 A typical real-time task is composed of a repetition of computation phases
130 (task instances, or jobs) which are activated on a periodic or sporadic 137 (task instances, or jobs) which are activated on a periodic or sporadic
131 fashion. 138 fashion.
@@ -166,6 +173,9 @@ CONTENTS
166 is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum 173 is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum
167 utilization[12]. 174 utilization[12].
168 175
1763.2 Schedulability Analysis for Uniprocessor Systems
177------------------------
178
169 If M=1 (uniprocessor system), or in case of partitioned scheduling (each 179 If M=1 (uniprocessor system), or in case of partitioned scheduling (each
170 real-time task is statically assigned to one and only one CPU), it is 180 real-time task is statically assigned to one and only one CPU), it is
171 possible to formally check if all the deadlines are respected. 181 possible to formally check if all the deadlines are respected.
@@ -204,6 +214,9 @@ CONTENTS
204 time-consuming to be performed on-line. Hence, as explained in Section 214 time-consuming to be performed on-line. Hence, as explained in Section
205 4 Linux uses an admission test based on the tasks' utilizations. 215 4 Linux uses an admission test based on the tasks' utilizations.
206 216
2173.3 Schedulability Analysis for Multiprocessor Systems
218------------------------
219
207 On multiprocessor systems with global EDF scheduling (non partitioned 220 On multiprocessor systems with global EDF scheduling (non partitioned
208 systems), a sufficient test for schedulability can not be based on the 221 systems), a sufficient test for schedulability can not be based on the
209 utilizations or densities: it can be shown that even if D_i = P_i task 222 utilizations or densities: it can be shown that even if D_i = P_i task
@@ -249,6 +262,9 @@ CONTENTS
249 the total utilization is smaller or equal than M then the response times of 262 the total utilization is smaller or equal than M then the response times of
250 the tasks are limited. 263 the tasks are limited.
251 264
2653.4 Relationship with SCHED_DEADLINE Parameters
266------------------------
267
252 Finally, it is important to understand the relationship between the 268 Finally, it is important to understand the relationship between the
253 SCHED_DEADLINE scheduling parameters described in Section 2 (runtime, 269 SCHED_DEADLINE scheduling parameters described in Section 2 (runtime,
254 deadline and period) and the real-time task parameters (WCET, D, P) 270 deadline and period) and the real-time task parameters (WCET, D, P)