* 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_attr) is meant at describing a so-called
- * sporadic time-constrained task. In such model a task is specified by:
+ * This variant (sched_attr) allows to define additional attributes to
+ * improve the scheduler knowledge about task requirements.
+ *
+ * Scheduling Class Attributes
+ * ===========================
+ *
+ * A subset of sched_attr attributes specifies the
+ * scheduling policy and relative POSIX attributes:
+ *
+ * @size size of the structure, for fwd/bwd compat.
+ *
+ * @sched_policy task's scheduling policy
+ * @sched_nice task's nice value (SCHED_NORMAL/BATCH)
+ * @sched_priority task's static priority (SCHED_FIFO/RR)
+ *
+ * Certain more advanced scheduling features can be controlled by a
+ * predefined set of flags via the attribute:
+ *
+ * @sched_flags for customizing the scheduler behaviour
+ *
+ * Sporadic Time-Constrained Tasks Attributes
+ * ==========================================
+ *
+ * A subset of sched_attr attributes allows to describe 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;
* 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_attr structure:
+ * This is reflected by the following fields of the sched_attr structure:
*
- * @size size of the structure, for fwd/bwd compat.
- *
- * @sched_policy task's scheduling policy
- * @sched_flags for customizing the scheduler behaviour
- * @sched_nice task's nice value (SCHED_NORMAL/BATCH)
- * @sched_priority task's static priority (SCHED_FIFO/RR)
* @sched_deadline representative of the task's deadline
* @sched_runtime representative of the task's runtime
* @sched_period representative of the task's period
* As of now, the SCHED_DEADLINE policy (sched_dl scheduling class) is the
* only user of this new interface. More information about the algorithm
* available in the scheduling class file or in Documentation/.
+ *
+ * Task Utilization Attributes
+ * ===========================
+ *
+ * A subset of sched_attr attributes allows to specify the utilization which
+ * should be expected by a task. These attributes allows to inform the
+ * scheduler about the utilization boundaries within which is safe to schedule
+ * the task. These utilization boundaries are valuable information to support
+ * scheduler decisions on both task placement and frequencies selection.
+ *
+ * @sched_util_min represents the minimum utilization
+ * @sched_util_max represents the maximum utilization
+ *
+ * Utilization is a value in the range [0..SCHED_CAPACITY_SCALE] which
+ * represents the percentage of CPU time used by a task when running at the
+ * maximum frequency on the highest capacity CPU of the system. Thus, for
+ * example, a 20% utilization task is a task running for 2ms every 10ms.
+ *
+ * A task with a min utilization value bigger then 0 is more likely to be
+ * scheduled on a CPU which can provide that bandwidth.
+ * A task with a max utilization value smaller then 1024 is more likely to be
+ * scheduled on a CPU which do not provide more then the required bandwidth.
*/
struct sched_attr {
__u32 size;
__u64 sched_runtime;
__u64 sched_deadline;
__u64 sched_period;
+
+ /* Utilization hints */
+ __u32 sched_util_min;
+ __u32 sched_util_max;
+
};
#endif /* _UAPI_LINUX_SCHED_TYPES_H */
config GENERIC_SCHED_CLOCK
bool
+menu "Scheduler features"
+
+config UCLAMP_TASK
+ bool "Enable utilization clamping for RT/FAIR tasks"
+ depends on CPU_FREQ_GOV_SCHEDUTIL
+ default false
+ help
+ This feature enables the scheduler to track the clamped utilization
+ of each CPU based on RUNNABLE tasks currently scheduled on that CPU.
+
+ When this option is enabled, the user can specify a min and max CPU
+ bandwidth which is allowed for a task.
+ The max bandwidth allows to clamp the maximum frequency a task can
+ use, while the min bandwidth allows to define a minimum frequency a
+ task will always use.
+
+ If in doubt, say N.
+
+endmenu
#
# For architectures that want to enable the support for NUMA-affine scheduler
# balancing logic:
}
}
+#ifdef CONFIG_UCLAMP_TASK
+static inline int __setscheduler_uclamp(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ if (attr->sched_util_min > attr->sched_util_max)
+ return -EINVAL;
+ if (attr->sched_util_max > SCHED_CAPACITY_SCALE)
+ return -EINVAL;
+
+ p->uclamp[UCLAMP_MIN] = attr->sched_util_min;
+ p->uclamp[UCLAMP_MAX] = attr->sched_util_max;
+
+ return 0;
+}
+#else /* CONFIG_UCLAMP_TASK */
+static inline int __setscheduler_uclamp(struct task_struct *p,
+ const struct sched_attr *attr)
+{
+ return -EINVAL;
+}
+#endif /* CONFIG_UCLAMP_TASK */
+
static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
{
if (!(flags & ENQUEUE_NOCLOCK))
p->se.cfs_rq = NULL;
#endif
+#ifdef CONFIG_UCLAMP_TASK
+ p->uclamp[UCLAMP_MIN] = 0;
+ p->uclamp[UCLAMP_MAX] = SCHED_CAPACITY_SCALE;
+#endif
+
#ifdef CONFIG_SCHEDSTATS
/* Even if schedstat is disabled, there should not be garbage */
memset(&p->se.statistics, 0, sizeof(p->se.statistics));
return retval;
}
+ /* Configure utilization clamps for the task */
+ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) {
+ retval = __setscheduler_uclamp(p, attr);
+ if (retval)
+ return retval;
+ }
+
/*
* Make sure no PI-waiters arrive (or leave) while we are
* changing the priority of the task:
else
attr.sched_nice = task_nice(p);
+#ifdef CONFIG_UCLAMP_TASK
+ attr.sched_util_min = p->uclamp[UCLAMP_MIN];
+ attr.sched_util_max = p->uclamp[UCLAMP_MAX];
+#endif
+
rcu_read_unlock();
retval = sched_read_attr(uattr, &attr, size);
projects / platform / kernel / linux-exynos.git / commitdiff