diff options
| -rw-r--r-- | include/linux/sched.h | 49 | ||||
| -rw-r--r-- | kernel/sched/debug.c | 7 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 82 | ||||
| -rw-r--r-- | kernel/sched/pelt.h | 4 |
4 files changed, 48 insertions, 94 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 8d258162deb0..03bfe9ab2951 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -415,42 +415,6 @@ struct load_weight { 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. - * - * The UTIL_AVG_UNCHANGED flag is used to synchronize util_est with util_avg - * updates. When a task is dequeued, its util_est should not be updated if its - * util_avg has not been updated in the meantime. - * This information is mapped into the MSB bit of util_est.enqueued at dequeue - * time. Since max value of util_est.enqueued for a task is 1024 (PELT util_avg - * for a task) it is safe to use MSB. - */ -struct util_est { - unsigned int enqueued; - unsigned int ewma; -#define UTIL_EST_WEIGHT_SHIFT 2 -#define UTIL_AVG_UNCHANGED 0x80000000 -} __attribute__((__aligned__(sizeof(u64)))); - /* * The load/runnable/util_avg accumulates an infinite geometric series * (see __update_load_avg_cfs_rq() in kernel/sched/pelt.c). @@ -505,9 +469,20 @@ struct sched_avg { unsigned long load_avg; unsigned long runnable_avg; unsigned long util_avg; - struct util_est util_est; + unsigned int util_est; } ____cacheline_aligned; +/* + * The UTIL_AVG_UNCHANGED flag is used to synchronize util_est with util_avg + * updates. When a task is dequeued, its util_est should not be updated if its + * util_avg has not been updated in the meantime. + * This information is mapped into the MSB bit of util_est at dequeue time. + * Since max value of util_est for a task is 1024 (PELT util_avg for a task) + * it is safe to use MSB. + */ +#define UTIL_EST_WEIGHT_SHIFT 2 +#define UTIL_AVG_UNCHANGED 0x80000000 + struct sched_statistics { #ifdef CONFIG_SCHEDSTATS u64 wait_start; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 168eecc209b4..8d5d98a5834d 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -684,8 +684,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) cfs_rq->avg.runnable_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: %u\n", "util_est", + cfs_rq->avg.util_est); SEQ_printf(m, " .%-30s: %ld\n", "removed.load_avg", cfs_rq->removed.load_avg); SEQ_printf(m, " .%-30s: %ld\n", "removed.util_avg", @@ -1075,8 +1075,7 @@ void proc_sched_show_task(struct task_struct *p, struct pid_namespace *ns, P(se.avg.runnable_avg); P(se.avg.util_avg); P(se.avg.last_update_time); - P(se.avg.util_est.ewma); - PM(se.avg.util_est.enqueued, ~UTIL_AVG_UNCHANGED); + PM(se.avg.util_est, ~UTIL_AVG_UNCHANGED); #endif #ifdef CONFIG_UCLAMP_TASK __PS("uclamp.min", p->uclamp_req[UCLAMP_MIN].value); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index e94d65da8d66..823dd76d0546 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4781,9 +4781,7 @@ static inline unsigned long task_runnable(struct task_struct *p) 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 & ~UTIL_AVG_UNCHANGED)); + return READ_ONCE(p->se.avg.util_est) & ~UTIL_AVG_UNCHANGED; } static inline unsigned long task_util_est(struct task_struct *p) @@ -4800,9 +4798,9 @@ static inline void util_est_enqueue(struct cfs_rq *cfs_rq, return; /* Update root cfs_rq's estimated utilization */ - enqueued = cfs_rq->avg.util_est.enqueued; + enqueued = cfs_rq->avg.util_est; enqueued += _task_util_est(p); - WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); + WRITE_ONCE(cfs_rq->avg.util_est, enqueued); trace_sched_util_est_cfs_tp(cfs_rq); } @@ -4816,34 +4814,20 @@ static inline void util_est_dequeue(struct cfs_rq *cfs_rq, return; /* Update root cfs_rq's estimated utilization */ - enqueued = cfs_rq->avg.util_est.enqueued; + enqueued = cfs_rq->avg.util_est; enqueued -= min_t(unsigned int, enqueued, _task_util_est(p)); - WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued); + WRITE_ONCE(cfs_rq->avg.util_est, enqueued); trace_sched_util_est_cfs_tp(cfs_rq); } #define UTIL_EST_MARGIN (SCHED_CAPACITY_SCALE / 100) -/* - * 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 + margin < INT_MAX. - */ -static inline bool within_margin(int value, int margin) -{ - return ((unsigned int)(value + margin - 1) < (2 * margin - 1)); -} - static inline void util_est_update(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) { - long last_ewma_diff, last_enqueued_diff; - struct util_est ue; + unsigned int ewma, dequeued, last_ewma_diff; if (!sched_feat(UTIL_EST)) return; @@ -4855,23 +4839,25 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, if (!task_sleep) return; + /* Get current estimate of utilization */ + ewma = READ_ONCE(p->se.avg.util_est); + /* * If the PELT values haven't changed since enqueue time, * skip the util_est update. */ - ue = p->se.avg.util_est; - if (ue.enqueued & UTIL_AVG_UNCHANGED) + if (ewma & UTIL_AVG_UNCHANGED) return; - last_enqueued_diff = ue.enqueued; + /* Get utilization at dequeue */ + dequeued = task_util(p); /* * Reset EWMA on utilization increases, the moving average is used only * to smooth utilization decreases. */ - ue.enqueued = task_util(p); - if (ue.ewma < ue.enqueued) { - ue.ewma = ue.enqueued; + if (ewma <= dequeued) { + ewma = dequeued; goto done; } @@ -4879,27 +4865,22 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, * Skip update of task's estimated utilization when its members are * already ~1% close to its last activation value. */ - last_ewma_diff = ue.enqueued - ue.ewma; - last_enqueued_diff -= ue.enqueued; - if (within_margin(last_ewma_diff, UTIL_EST_MARGIN)) { - if (!within_margin(last_enqueued_diff, UTIL_EST_MARGIN)) - goto done; - - return; - } + last_ewma_diff = ewma - dequeued; + if (last_ewma_diff < UTIL_EST_MARGIN) + goto done; /* * To avoid overestimation of actual task utilization, skip updates if * we cannot grant there is idle time in this CPU. */ - if (task_util(p) > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)))) + if (dequeued > arch_scale_cpu_capacity(cpu_of(rq_of(cfs_rq)))) return; /* * To avoid underestimate of task utilization, skip updates of EWMA if * we cannot grant that thread got all CPU time it wanted. */ - if ((ue.enqueued + UTIL_EST_MARGIN) < task_runnable(p)) + if ((dequeued + UTIL_EST_MARGIN) < task_runnable(p)) goto done; @@ -4907,25 +4888,24 @@ static inline void util_est_update(struct cfs_rq *cfs_rq, * 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): + * of the task size. This is done 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) + * = 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; + ewma <<= UTIL_EST_WEIGHT_SHIFT; + ewma -= last_ewma_diff; + ewma >>= UTIL_EST_WEIGHT_SHIFT; done: - ue.enqueued |= UTIL_AVG_UNCHANGED; - WRITE_ONCE(p->se.avg.util_est, ue); + ewma |= UTIL_AVG_UNCHANGED; + WRITE_ONCE(p->se.avg.util_est, ewma); trace_sched_util_est_se_tp(&p->se); } @@ -7653,16 +7633,16 @@ cpu_util(int cpu, struct task_struct *p, int dst_cpu, int boost) if (sched_feat(UTIL_EST)) { unsigned long util_est; - util_est = READ_ONCE(cfs_rq->avg.util_est.enqueued); + util_est = READ_ONCE(cfs_rq->avg.util_est); /* * During wake-up @p isn't enqueued yet and doesn't contribute - * to any cpu_rq(cpu)->cfs.avg.util_est.enqueued. + * to any cpu_rq(cpu)->cfs.avg.util_est. * If @dst_cpu == @cpu add it to "simulate" cpu_util after @p * has been enqueued. * * During exec (@dst_cpu = -1) @p is enqueued and does - * contribute to cpu_rq(cpu)->cfs.util_est.enqueued. + * contribute to cpu_rq(cpu)->cfs.util_est. * Remove it to "simulate" cpu_util without @p's contribution. * * Despite the task_on_rq_queued(@p) check there is still a diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h index 3a0e0dc28721..9e1083465fbc 100644 --- a/kernel/sched/pelt.h +++ b/kernel/sched/pelt.h @@ -52,13 +52,13 @@ static inline void cfs_se_util_change(struct sched_avg *avg) return; /* Avoid store if the flag has been already reset */ - enqueued = avg->util_est.enqueued; + enqueued = avg->util_est; if (!(enqueued & UTIL_AVG_UNCHANGED)) return; /* Reset flag to report util_avg has been updated */ enqueued &= ~UTIL_AVG_UNCHANGED; - WRITE_ONCE(avg->util_est.enqueued, enqueued); + WRITE_ONCE(avg->util_est, enqueued); } static inline u64 rq_clock_pelt(struct rq *rq) |