sched/dl/Documentation: Split Section 3 (6aaa1025) · Commits · e / devices / android_kernel_fairphone_FP5

Documentation/scheduler/sched-deadline.txt

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	@@ -8,6 +8,10 @@ CONTENTS
	1. Overview		1. Overview
	2. Scheduling algorithm		2. Scheduling algorithm
	3. Scheduling Real-Time Tasks		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. Bandwidth management
	4.1 System-wide settings		4.1 System-wide settings
	4.2 Task interface		4.2 Task interface
	@@ -126,6 +130,9 @@ CONTENTS
	suited for periodic or sporadic real-time tasks that need guarantees on their		suited for periodic or sporadic real-time tasks that need guarantees on their
	timing behavior, e.g., multimedia, streaming, control applications, etc.		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		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		(task instances, or jobs) which are activated on a periodic or sporadic
	fashion.		fashion.
	@@ -166,6 +173,9 @@ CONTENTS
	is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum		is the minimum WCET, and U_max = max{WCET_i/P_i} is the maximum
	utilization[12].		utilization[12].

			3.2 Schedulability Analysis for Uniprocessor Systems
			------------------------

	If M=1 (uniprocessor system), or in case of partitioned scheduling (each		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		real-time task is statically assigned to one and only one CPU), it is
	possible to formally check if all the deadlines are respected.		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		time-consuming to be performed on-line. Hence, as explained in Section
	4 Linux uses an admission test based on the tasks' utilizations.		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		On multiprocessor systems with global EDF scheduling (non partitioned
	systems), a sufficient test for schedulability can not be based on the		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		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 total utilization is smaller or equal than M then the response times of
	the tasks are limited.		the tasks are limited.

			3.4 Relationship with SCHED_DEADLINE Parameters
			------------------------

	Finally, it is important to understand the relationship between the		Finally, it is important to understand the relationship between the
	SCHED_DEADLINE scheduling parameters described in Section 2 (runtime,		SCHED_DEADLINE scheduling parameters described in Section 2 (runtime,
	deadline and period) and the real-time task parameters (WCET, D, P)		deadline and period) and the real-time task parameters (WCET, D, P)