diff options
Diffstat (limited to 'kernel/sched/sched.h')
| -rw-r--r-- | kernel/sched/sched.h | 44 |
1 files changed, 40 insertions, 4 deletions
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index eb971151e7e4..de53be905739 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2966,16 +2966,52 @@ static inline unsigned long cpu_util_dl(struct rq *rq) return READ_ONCE(rq->avg_dl.util_avg); } -static inline unsigned long cpu_util_cfs(struct rq *rq) +/** + * cpu_util_cfs() - Estimates the amount of CPU capacity used by CFS tasks. + * @cpu: the CPU to get the utilization for. + * + * The unit of the return value must be the same as the one of CPU capacity + * so that CPU utilization can be compared with CPU capacity. + * + * CPU utilization is the sum of running time of runnable tasks plus the + * recent utilization of currently non-runnable tasks on that CPU. + * It represents the amount of CPU capacity currently used by CFS tasks in + * the range [0..max CPU capacity] with max CPU capacity being the CPU + * capacity at f_max. + * + * The estimated CPU utilization is defined as the maximum between CPU + * utilization and sum of the estimated utilization of the currently + * runnable tasks on that CPU. It preserves a utilization "snapshot" of + * previously-executed tasks, which helps better deduce how busy a CPU will + * be when a long-sleeping task wakes up. The contribution to CPU utilization + * of such a task would be significantly decayed at this point of time. + * + * CPU utilization can be higher than the current CPU capacity + * (f_curr/f_max * max CPU capacity) or even the max CPU capacity because + * of rounding errors as well as task migrations or wakeups of new tasks. + * CPU utilization has to be capped to fit into the [0..max CPU capacity] + * range. Otherwise a group of CPUs (CPU0 util = 121% + CPU1 util = 80%) + * could be seen as over-utilized even though CPU1 has 20% of spare CPU + * capacity. CPU utilization is allowed to overshoot current CPU capacity + * though since this is useful for predicting the CPU capacity required + * after task migrations (scheduler-driven DVFS). + * + * Return: (Estimated) utilization for the specified CPU. + */ +static inline unsigned long cpu_util_cfs(int cpu) { - unsigned long util = READ_ONCE(rq->cfs.avg.util_avg); + struct cfs_rq *cfs_rq; + unsigned long util; + + cfs_rq = &cpu_rq(cpu)->cfs; + util = READ_ONCE(cfs_rq->avg.util_avg); if (sched_feat(UTIL_EST)) { util = max_t(unsigned long, util, - READ_ONCE(rq->cfs.avg.util_est.enqueued)); + READ_ONCE(cfs_rq->avg.util_est.enqueued)); } - return util; + return min(util, capacity_orig_of(cpu)); } static inline unsigned long cpu_util_rt(struct rq *rq) |