u32 inv_weight;
};
+/**
+ * struct util_est - Estimation utilization of FAIR tasks
+ * @enqueued: instantaneous estimated utilization of a task/cpu
+ * @ewma: the Exponential Weighted Moving Average (EWMA)
+ * utilization of a task
+ *
+ * Support data structure to track an Exponential Weighted Moving Average
+ * (EWMA) of a FAIR task's utilization. New samples are added to the moving
+ * average each time a task completes an activation. Sample's weight is chosen
+ * so that the EWMA will be relatively insensitive to transient changes to the
+ * task's workload.
+ *
+ * The enqueued attribute has a slightly different meaning for tasks and cpus:
+ * - task: the task's util_avg at last task dequeue time
+ * - cfs_rq: the sum of util_est.enqueued for each RUNNABLE task on that CPU
+ * Thus, the util_est.enqueued of a task represents the contribution on the
+ * estimated utilization of the CPU where that task is currently enqueued.
+ *
+ * Only for tasks we track a moving average of the past instantaneous
+ * estimated utilization. This allows to absorb sporadic drops in utilization
+ * of an otherwise almost periodic task.
+ */
+struct util_est {
+ unsigned int enqueued;
+ unsigned int ewma;
+#define UTIL_EST_WEIGHT_SHIFT 2
+};
+
/*
* The load_avg/util_avg accumulates an infinite geometric series
* (see __update_load_avg() in kernel/sched/fair.c).
unsigned long load_avg;
unsigned long runnable_load_avg;
unsigned long util_avg;
+ struct util_est util_est;
};
struct sched_statistics {
cfs_rq->avg.runnable_load_avg);
SEQ_printf(m, " .%-30s: %lu\n", "util_avg",
cfs_rq->avg.util_avg);
+ SEQ_printf(m, " .%-30s: %u\n", "util_est_enqueued",
+ cfs_rq->avg.util_est.enqueued);
SEQ_printf(m, " .%-30s: %ld\n", "removed.load_avg",
cfs_rq->removed.load_avg);
SEQ_printf(m, " .%-30s: %ld\n", "removed.util_avg",
P(se.avg.runnable_load_avg);
P(se.avg.util_avg);
P(se.avg.last_update_time);
+ P(se.avg.util_est.ewma);
+ P(se.avg.util_est.enqueued);
#endif
P(policy);
P(prio);
static int idle_balance(struct rq *this_rq, struct rq_flags *rf);
+static inline unsigned long task_util(struct task_struct *p)
+{
+ return READ_ONCE(p->se.avg.util_avg);
+}
+
+static inline unsigned long _task_util_est(struct task_struct *p)
+{
+ struct util_est ue = READ_ONCE(p->se.avg.util_est);
+
+ return max(ue.ewma, ue.enqueued);
+}
+
+static inline unsigned long task_util_est(struct task_struct *p)
+{
+ return max(task_util(p), _task_util_est(p));
+}
+
+static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
+ struct task_struct *p)
+{
+ unsigned int enqueued;
+
+ if (!sched_feat(UTIL_EST))
+ return;
+
+ /* Update root cfs_rq's estimated utilization */
+ enqueued = cfs_rq->avg.util_est.enqueued;
+ enqueued += _task_util_est(p);
+ WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
+}
+
+/*
+ * Check if a (signed) value is within a specified (unsigned) margin,
+ * based on the observation that:
+ *
+ * abs(x) < y := (unsigned)(x + y - 1) < (2 * y - 1)
+ *
+ * NOTE: this only works when value + maring < INT_MAX.
+ */
+static inline bool within_margin(int value, int margin)
+{
+ return ((unsigned int)(value + margin - 1) < (2 * margin - 1));
+}
+
+static void
+util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
+{
+ long last_ewma_diff;
+ struct util_est ue;
+
+ if (!sched_feat(UTIL_EST))
+ return;
+
+ /*
+ * Update root cfs_rq's estimated utilization
+ *
+ * If *p is the last task then the root cfs_rq's estimated utilization
+ * of a CPU is 0 by definition.
+ */
+ ue.enqueued = 0;
+ if (cfs_rq->nr_running) {
+ ue.enqueued = cfs_rq->avg.util_est.enqueued;
+ ue.enqueued -= min_t(unsigned int, ue.enqueued,
+ _task_util_est(p));
+ }
+ WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
+
+ /*
+ * Skip update of task's estimated utilization when the task has not
+ * yet completed an activation, e.g. being migrated.
+ */
+ if (!task_sleep)
+ return;
+
+ /*
+ * Skip update of task's estimated utilization when its EWMA is
+ * already ~1% close to its last activation value.
+ */
+ ue = p->se.avg.util_est;
+ ue.enqueued = task_util(p);
+ last_ewma_diff = ue.enqueued - ue.ewma;
+ if (within_margin(last_ewma_diff, (SCHED_CAPACITY_SCALE / 100)))
+ return;
+
+ /*
+ * Update Task's estimated utilization
+ *
+ * When *p completes an activation we can consolidate another sample
+ * of the task size. This is done by storing the current PELT value
+ * as ue.enqueued and by using this value to update the Exponential
+ * Weighted Moving Average (EWMA):
+ *
+ * ewma(t) = w * task_util(p) + (1-w) * ewma(t-1)
+ * = w * task_util(p) + ewma(t-1) - w * ewma(t-1)
+ * = w * (task_util(p) - ewma(t-1)) + ewma(t-1)
+ * = w * ( last_ewma_diff ) + ewma(t-1)
+ * = w * (last_ewma_diff + ewma(t-1) / w)
+ *
+ * Where 'w' is the weight of new samples, which is configured to be
+ * 0.25, thus making w=1/4 ( >>= UTIL_EST_WEIGHT_SHIFT)
+ */
+ ue.ewma <<= UTIL_EST_WEIGHT_SHIFT;
+ ue.ewma += last_ewma_diff;
+ ue.ewma >>= UTIL_EST_WEIGHT_SHIFT;
+ WRITE_ONCE(p->se.avg.util_est, ue);
+}
+
#else /* CONFIG_SMP */
static inline int
return 0;
}
+static inline void
+util_est_enqueue(struct cfs_rq *cfs_rq, struct task_struct *p) {}
+
+static inline void
+util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p,
+ bool task_sleep) {}
+
#endif /* CONFIG_SMP */
static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
if (!se)
add_nr_running(rq, 1);
+ util_est_enqueue(&rq->cfs, p);
hrtick_update(rq);
}
if (!se)
sub_nr_running(rq, 1);
+ util_est_dequeue(&rq->cfs, p, task_sleep);
hrtick_update(rq);
}
return target;
}
-static inline unsigned long task_util(struct task_struct *p);
static unsigned long cpu_util_wake(int cpu, struct task_struct *p);
static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
return (util >= capacity) ? capacity : util;
}
-static inline unsigned long task_util(struct task_struct *p)
-{
- return p->se.avg.util_avg;
-}
-
/*
* cpu_util_wake: Compute CPU utilization with any contributions from
* the waking task p removed.
projects / users / hch / configfs.git / commitdiff