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| -rw-r--r-- | Documentation/scheduler/sched-deadline.txt | 16 |
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 | ||
| 133 | 3.1 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 | ||
| 176 | 3.2 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 | ||
| 217 | 3.3 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 | ||
| 265 | 3.4 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) |
