Messages in this thread | | | Subject | Re: [RFC][PATCH 02/22] sched: add extended scheduling interface | From | Steven Rostedt <> | Date | Fri, 12 Nov 2010 11:38:44 -0500 |
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On Fri, 2010-10-29 at 08:27 +0200, Raistlin wrote:
> +/* > + * Extended scheduling parameters data structure. > + * > + * This is needed because the original struct sched_param can not be > + * altered without introducing ABI issues with legacy applications > + * (e.g., in sched_getparam()). > + * > + * However, the possibility of specifying more than just a priority for > + * the tasks may be useful for a wide variety of application fields, e.g., > + * multimedia, streaming, automation and control, and many others. > + * > + * This variant (sched_param_ex) is meant at describing a so-called > + * sporadic time-constrained task. In such model a task is specified by: > + * - the activation period or minimum instance inter-arrival time; > + * - the maximum (or average, depending on the actual scheduling > + * discipline) computation time of all instances, a.k.a. runtime; > + * - the deadline (relative to the actual activation time) of each > + * instance. > + * Very briefly, a periodic (sporadic) task asks for the execution of > + * some specific computation --which is typically called an instance-- > + * (at most) every period. Moreover, each instance typically lasts no more > + * than the runtime and must be completed by time instant t equal to > + * the instance activation time + the deadline. > + * > + * This is reflected by the actual fields of the sched_param_ex structure: > + * > + * @sched_priority task's priority (might still be useful) > + * @sched_deadline representative of the task's deadline > + * @sched_runtime representative of the task's runtime > + * @sched_period representative of the task's period > + * @sched_flags for customizing the scheduler behaviour > + * > + * There are other fields, which may be useful for implementing (in > + * user-space) advanced scheduling behaviours, e.g., feedback scheduling: > + * > + * @curr_runtime task's currently available runtime > + * @used_runtime task's totally used runtime > + * @curr_deadline task's current absolute deadline > + * > + * Given this task model, there are a multiplicity of scheduling algorithms > + * and policies, that can be used to ensure all the tasks will make their > + * timing constraints. > + */
A while ago I implemented an EDF scheduler for a client (before working with Red Hat), and one thing they asked about was having a "soft group", which was basically: This group is guaranteed X runtime in Y period, but if the system is idle, let the group run, even if it has exhausted its X runtime.
Is this supported?
-- Steve
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