1424 lines
34 KiB
C
1424 lines
34 KiB
C
/*
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* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
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*
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* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
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*
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* Interactivity improvements by Mike Galbraith
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* (C) 2007 Mike Galbraith <efault@gmx.de>
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*
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* Various enhancements by Dmitry Adamushko.
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* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
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*
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* Group scheduling enhancements by Srivatsa Vaddagiri
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* Copyright IBM Corporation, 2007
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* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
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*
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* Scaled math optimizations by Thomas Gleixner
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* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
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*
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* Adaptive scheduling granularity, math enhancements by Peter Zijlstra
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* Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
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*/
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#include <linux/latencytop.h>
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/*
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* Targeted preemption latency for CPU-bound tasks:
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* (default: 20ms * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* NOTE: this latency value is not the same as the concept of
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* 'timeslice length' - timeslices in CFS are of variable length
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* and have no persistent notion like in traditional, time-slice
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* based scheduling concepts.
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*
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* (to see the precise effective timeslice length of your workload,
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* run vmstat and monitor the context-switches (cs) field)
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*/
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unsigned int sysctl_sched_latency = 20000000ULL;
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/*
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* Minimal preemption granularity for CPU-bound tasks:
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* (default: 4 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*/
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unsigned int sysctl_sched_min_granularity = 4000000ULL;
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/*
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* is kept at sysctl_sched_latency / sysctl_sched_min_granularity
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*/
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static unsigned int sched_nr_latency = 5;
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/*
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* After fork, child runs first. (default) If set to 0 then
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* parent will (try to) run first.
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*/
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const_debug unsigned int sysctl_sched_child_runs_first = 1;
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/*
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* sys_sched_yield() compat mode
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*
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* This option switches the agressive yield implementation of the
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* old scheduler back on.
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*/
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unsigned int __read_mostly sysctl_sched_compat_yield;
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/*
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* SCHED_BATCH wake-up granularity.
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* (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*/
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unsigned int sysctl_sched_batch_wakeup_granularity = 10000000UL;
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/*
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* SCHED_OTHER wake-up granularity.
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* (default: 10 msec * (1 + ilog(ncpus)), units: nanoseconds)
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*
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* This option delays the preemption effects of decoupled workloads
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* and reduces their over-scheduling. Synchronous workloads will still
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* have immediate wakeup/sleep latencies.
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*/
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unsigned int sysctl_sched_wakeup_granularity = 10000000UL;
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const_debug unsigned int sysctl_sched_migration_cost = 500000UL;
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/**************************************************************
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* CFS operations on generic schedulable entities:
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*/
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/* cpu runqueue to which this cfs_rq is attached */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return cfs_rq->rq;
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}
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/* An entity is a task if it doesn't "own" a runqueue */
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#define entity_is_task(se) (!se->my_q)
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#else /* CONFIG_FAIR_GROUP_SCHED */
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static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
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{
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return container_of(cfs_rq, struct rq, cfs);
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}
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#define entity_is_task(se) 1
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#endif /* CONFIG_FAIR_GROUP_SCHED */
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static inline struct task_struct *task_of(struct sched_entity *se)
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{
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return container_of(se, struct task_struct, se);
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}
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/**************************************************************
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* Scheduling class tree data structure manipulation methods:
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*/
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static inline u64 max_vruntime(u64 min_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta > 0)
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min_vruntime = vruntime;
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return min_vruntime;
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}
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static inline u64 min_vruntime(u64 min_vruntime, u64 vruntime)
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{
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s64 delta = (s64)(vruntime - min_vruntime);
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if (delta < 0)
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min_vruntime = vruntime;
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return min_vruntime;
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}
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static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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return se->vruntime - cfs_rq->min_vruntime;
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}
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/*
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* Enqueue an entity into the rb-tree:
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*/
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static void __enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
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struct rb_node *parent = NULL;
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struct sched_entity *entry;
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s64 key = entity_key(cfs_rq, se);
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int leftmost = 1;
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/*
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* Find the right place in the rbtree:
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*/
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while (*link) {
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parent = *link;
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entry = rb_entry(parent, struct sched_entity, run_node);
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/*
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* We dont care about collisions. Nodes with
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* the same key stay together.
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*/
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if (key < entity_key(cfs_rq, entry)) {
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link = &parent->rb_left;
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} else {
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link = &parent->rb_right;
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leftmost = 0;
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}
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}
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/*
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* Maintain a cache of leftmost tree entries (it is frequently
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* used):
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*/
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if (leftmost) {
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cfs_rq->rb_leftmost = &se->run_node;
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/*
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* maintain cfs_rq->min_vruntime to be a monotonic increasing
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* value tracking the leftmost vruntime in the tree.
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*/
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cfs_rq->min_vruntime =
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max_vruntime(cfs_rq->min_vruntime, se->vruntime);
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}
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rb_link_node(&se->run_node, parent, link);
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rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
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}
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static void __dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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if (cfs_rq->rb_leftmost == &se->run_node) {
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struct rb_node *next_node;
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struct sched_entity *next;
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next_node = rb_next(&se->run_node);
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cfs_rq->rb_leftmost = next_node;
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if (next_node) {
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next = rb_entry(next_node,
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struct sched_entity, run_node);
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cfs_rq->min_vruntime =
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max_vruntime(cfs_rq->min_vruntime,
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next->vruntime);
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}
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}
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rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
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}
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static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
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{
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return cfs_rq->rb_leftmost;
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}
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static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
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{
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return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
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}
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static inline struct sched_entity *__pick_last_entity(struct cfs_rq *cfs_rq)
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{
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struct rb_node *last = rb_last(&cfs_rq->tasks_timeline);
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if (!last)
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return NULL;
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return rb_entry(last, struct sched_entity, run_node);
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}
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/**************************************************************
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* Scheduling class statistics methods:
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*/
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#ifdef CONFIG_SCHED_DEBUG
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int sched_nr_latency_handler(struct ctl_table *table, int write,
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struct file *filp, void __user *buffer, size_t *lenp,
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loff_t *ppos)
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{
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int ret = proc_dointvec_minmax(table, write, filp, buffer, lenp, ppos);
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if (ret || !write)
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return ret;
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sched_nr_latency = DIV_ROUND_UP(sysctl_sched_latency,
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sysctl_sched_min_granularity);
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return 0;
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}
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#endif
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/*
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* The idea is to set a period in which each task runs once.
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*
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* When there are too many tasks (sysctl_sched_nr_latency) we have to stretch
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* this period because otherwise the slices get too small.
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*
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* p = (nr <= nl) ? l : l*nr/nl
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*/
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static u64 __sched_period(unsigned long nr_running)
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{
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u64 period = sysctl_sched_latency;
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unsigned long nr_latency = sched_nr_latency;
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if (unlikely(nr_running > nr_latency)) {
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period = sysctl_sched_min_granularity;
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period *= nr_running;
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}
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return period;
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}
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/*
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* We calculate the wall-time slice from the period by taking a part
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* proportional to the weight.
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*
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* s = p*w/rw
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*/
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static u64 sched_slice(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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u64 slice = __sched_period(cfs_rq->nr_running);
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slice *= se->load.weight;
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do_div(slice, cfs_rq->load.weight);
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return slice;
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}
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/*
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* We calculate the vruntime slice.
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*
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* vs = s/w = p/rw
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*/
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static u64 __sched_vslice(unsigned long rq_weight, unsigned long nr_running)
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{
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u64 vslice = __sched_period(nr_running);
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vslice *= NICE_0_LOAD;
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do_div(vslice, rq_weight);
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return vslice;
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}
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static u64 sched_vslice(struct cfs_rq *cfs_rq)
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{
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return __sched_vslice(cfs_rq->load.weight, cfs_rq->nr_running);
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}
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static u64 sched_vslice_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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return __sched_vslice(cfs_rq->load.weight + se->load.weight,
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cfs_rq->nr_running + 1);
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}
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/*
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* Update the current task's runtime statistics. Skip current tasks that
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* are not in our scheduling class.
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*/
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static inline void
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__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
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unsigned long delta_exec)
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{
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unsigned long delta_exec_weighted;
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schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
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curr->sum_exec_runtime += delta_exec;
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schedstat_add(cfs_rq, exec_clock, delta_exec);
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delta_exec_weighted = delta_exec;
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if (unlikely(curr->load.weight != NICE_0_LOAD)) {
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delta_exec_weighted = calc_delta_fair(delta_exec_weighted,
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&curr->load);
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}
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curr->vruntime += delta_exec_weighted;
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}
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static void update_curr(struct cfs_rq *cfs_rq)
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{
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struct sched_entity *curr = cfs_rq->curr;
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u64 now = rq_of(cfs_rq)->clock;
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unsigned long delta_exec;
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if (unlikely(!curr))
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return;
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/*
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* Get the amount of time the current task was running
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* since the last time we changed load (this cannot
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* overflow on 32 bits):
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*/
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delta_exec = (unsigned long)(now - curr->exec_start);
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__update_curr(cfs_rq, curr, delta_exec);
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curr->exec_start = now;
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if (entity_is_task(curr)) {
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struct task_struct *curtask = task_of(curr);
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cpuacct_charge(curtask, delta_exec);
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}
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}
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static inline void
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update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
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}
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/*
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* Task is being enqueued - update stats:
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*/
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static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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/*
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* Are we enqueueing a waiting task? (for current tasks
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* a dequeue/enqueue event is a NOP)
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*/
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if (se != cfs_rq->curr)
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update_stats_wait_start(cfs_rq, se);
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}
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static void
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update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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schedstat_set(se->wait_max, max(se->wait_max,
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rq_of(cfs_rq)->clock - se->wait_start));
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schedstat_set(se->wait_count, se->wait_count + 1);
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schedstat_set(se->wait_sum, se->wait_sum +
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rq_of(cfs_rq)->clock - se->wait_start);
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schedstat_set(se->wait_start, 0);
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}
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static inline void
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update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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/*
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* Mark the end of the wait period if dequeueing a
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* waiting task:
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*/
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if (se != cfs_rq->curr)
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update_stats_wait_end(cfs_rq, se);
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}
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/*
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* We are picking a new current task - update its stats:
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*/
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static inline void
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update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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/*
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* We are starting a new run period:
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*/
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se->exec_start = rq_of(cfs_rq)->clock;
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}
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/**************************************************
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* Scheduling class queueing methods:
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*/
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static void
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account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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update_load_add(&cfs_rq->load, se->load.weight);
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cfs_rq->nr_running++;
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se->on_rq = 1;
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}
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static void
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account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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update_load_sub(&cfs_rq->load, se->load.weight);
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cfs_rq->nr_running--;
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se->on_rq = 0;
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}
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static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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#ifdef CONFIG_SCHEDSTATS
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if (se->sleep_start) {
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u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
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struct task_struct *tsk = task_of(se);
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if ((s64)delta < 0)
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delta = 0;
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if (unlikely(delta > se->sleep_max))
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se->sleep_max = delta;
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se->sleep_start = 0;
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se->sum_sleep_runtime += delta;
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account_scheduler_latency(tsk, delta >> 10, 1);
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}
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if (se->block_start) {
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u64 delta = rq_of(cfs_rq)->clock - se->block_start;
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struct task_struct *tsk = task_of(se);
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if ((s64)delta < 0)
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delta = 0;
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if (unlikely(delta > se->block_max))
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se->block_max = delta;
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se->block_start = 0;
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se->sum_sleep_runtime += delta;
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/*
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* Blocking time is in units of nanosecs, so shift by 20 to
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* get a milliseconds-range estimation of the amount of
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* time that the task spent sleeping:
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*/
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if (unlikely(prof_on == SLEEP_PROFILING)) {
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profile_hits(SLEEP_PROFILING, (void *)get_wchan(tsk),
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delta >> 20);
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}
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account_scheduler_latency(tsk, delta >> 10, 0);
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}
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#endif
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}
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static void check_spread(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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#ifdef CONFIG_SCHED_DEBUG
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s64 d = se->vruntime - cfs_rq->min_vruntime;
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if (d < 0)
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d = -d;
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if (d > 3*sysctl_sched_latency)
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schedstat_inc(cfs_rq, nr_spread_over);
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#endif
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}
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static void
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place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
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{
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u64 vruntime;
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if (first_fair(cfs_rq)) {
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vruntime = min_vruntime(cfs_rq->min_vruntime,
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__pick_next_entity(cfs_rq)->vruntime);
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} else
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vruntime = cfs_rq->min_vruntime;
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|
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if (sched_feat(TREE_AVG)) {
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struct sched_entity *last = __pick_last_entity(cfs_rq);
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if (last) {
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vruntime += last->vruntime;
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vruntime >>= 1;
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}
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} else if (sched_feat(APPROX_AVG) && cfs_rq->nr_running)
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vruntime += sched_vslice(cfs_rq)/2;
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|
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/*
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* The 'current' period is already promised to the current tasks,
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* however the extra weight of the new task will slow them down a
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* little, place the new task so that it fits in the slot that
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* stays open at the end.
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*/
|
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if (initial && sched_feat(START_DEBIT))
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vruntime += sched_vslice_add(cfs_rq, se);
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|
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if (!initial) {
|
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/* sleeps upto a single latency don't count. */
|
|
if (sched_feat(NEW_FAIR_SLEEPERS))
|
|
vruntime -= sysctl_sched_latency;
|
|
|
|
/* ensure we never gain time by being placed backwards. */
|
|
vruntime = max_vruntime(se->vruntime, vruntime);
|
|
}
|
|
|
|
se->vruntime = vruntime;
|
|
}
|
|
|
|
static void
|
|
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
if (wakeup) {
|
|
place_entity(cfs_rq, se, 0);
|
|
enqueue_sleeper(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_enqueue(cfs_rq, se);
|
|
check_spread(cfs_rq, se);
|
|
if (se != cfs_rq->curr)
|
|
__enqueue_entity(cfs_rq, se);
|
|
account_entity_enqueue(cfs_rq, se);
|
|
}
|
|
|
|
static void
|
|
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int sleep)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
update_stats_dequeue(cfs_rq, se);
|
|
if (sleep) {
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
if (entity_is_task(se)) {
|
|
struct task_struct *tsk = task_of(se);
|
|
|
|
if (tsk->state & TASK_INTERRUPTIBLE)
|
|
se->sleep_start = rq_of(cfs_rq)->clock;
|
|
if (tsk->state & TASK_UNINTERRUPTIBLE)
|
|
se->block_start = rq_of(cfs_rq)->clock;
|
|
}
|
|
#endif
|
|
}
|
|
|
|
if (se != cfs_rq->curr)
|
|
__dequeue_entity(cfs_rq, se);
|
|
account_entity_dequeue(cfs_rq, se);
|
|
}
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void
|
|
check_preempt_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
|
|
{
|
|
unsigned long ideal_runtime, delta_exec;
|
|
|
|
ideal_runtime = sched_slice(cfs_rq, curr);
|
|
delta_exec = curr->sum_exec_runtime - curr->prev_sum_exec_runtime;
|
|
if (delta_exec > ideal_runtime)
|
|
resched_task(rq_of(cfs_rq)->curr);
|
|
}
|
|
|
|
static void
|
|
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
|
|
{
|
|
/* 'current' is not kept within the tree. */
|
|
if (se->on_rq) {
|
|
/*
|
|
* Any task has to be enqueued before it get to execute on
|
|
* a CPU. So account for the time it spent waiting on the
|
|
* runqueue.
|
|
*/
|
|
update_stats_wait_end(cfs_rq, se);
|
|
__dequeue_entity(cfs_rq, se);
|
|
}
|
|
|
|
update_stats_curr_start(cfs_rq, se);
|
|
cfs_rq->curr = se;
|
|
#ifdef CONFIG_SCHEDSTATS
|
|
/*
|
|
* Track our maximum slice length, if the CPU's load is at
|
|
* least twice that of our own weight (i.e. dont track it
|
|
* when there are only lesser-weight tasks around):
|
|
*/
|
|
if (rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
|
|
se->slice_max = max(se->slice_max,
|
|
se->sum_exec_runtime - se->prev_sum_exec_runtime);
|
|
}
|
|
#endif
|
|
se->prev_sum_exec_runtime = se->sum_exec_runtime;
|
|
}
|
|
|
|
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *se = NULL;
|
|
|
|
if (first_fair(cfs_rq)) {
|
|
se = __pick_next_entity(cfs_rq);
|
|
set_next_entity(cfs_rq, se);
|
|
}
|
|
|
|
return se;
|
|
}
|
|
|
|
static void put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev)
|
|
{
|
|
/*
|
|
* If still on the runqueue then deactivate_task()
|
|
* was not called and update_curr() has to be done:
|
|
*/
|
|
if (prev->on_rq)
|
|
update_curr(cfs_rq);
|
|
|
|
check_spread(cfs_rq, prev);
|
|
if (prev->on_rq) {
|
|
update_stats_wait_start(cfs_rq, prev);
|
|
/* Put 'current' back into the tree. */
|
|
__enqueue_entity(cfs_rq, prev);
|
|
}
|
|
cfs_rq->curr = NULL;
|
|
}
|
|
|
|
static void
|
|
entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr, int queued)
|
|
{
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
/*
|
|
* queued ticks are scheduled to match the slice, so don't bother
|
|
* validating it and just reschedule.
|
|
*/
|
|
if (queued)
|
|
return resched_task(rq_of(cfs_rq)->curr);
|
|
/*
|
|
* don't let the period tick interfere with the hrtick preemption
|
|
*/
|
|
if (!sched_feat(DOUBLE_TICK) &&
|
|
hrtimer_active(&rq_of(cfs_rq)->hrtick_timer))
|
|
return;
|
|
#endif
|
|
|
|
if (cfs_rq->nr_running > 1 || !sched_feat(WAKEUP_PREEMPT))
|
|
check_preempt_tick(cfs_rq, curr);
|
|
}
|
|
|
|
/**************************************************
|
|
* CFS operations on tasks:
|
|
*/
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
|
|
/* Walk up scheduling entities hierarchy */
|
|
#define for_each_sched_entity(se) \
|
|
for (; se; se = se->parent)
|
|
|
|
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
|
|
{
|
|
return p->se.cfs_rq;
|
|
}
|
|
|
|
/* runqueue on which this entity is (to be) queued */
|
|
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
|
|
{
|
|
return se->cfs_rq;
|
|
}
|
|
|
|
/* runqueue "owned" by this group */
|
|
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
|
|
{
|
|
return grp->my_q;
|
|
}
|
|
|
|
/* Given a group's cfs_rq on one cpu, return its corresponding cfs_rq on
|
|
* another cpu ('this_cpu')
|
|
*/
|
|
static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
|
|
{
|
|
return cfs_rq->tg->cfs_rq[this_cpu];
|
|
}
|
|
|
|
/* Iterate thr' all leaf cfs_rq's on a runqueue */
|
|
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
|
|
list_for_each_entry_rcu(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
|
|
|
|
/* Do the two (enqueued) entities belong to the same group ? */
|
|
static inline int
|
|
is_same_group(struct sched_entity *se, struct sched_entity *pse)
|
|
{
|
|
if (se->cfs_rq == pse->cfs_rq)
|
|
return 1;
|
|
|
|
return 0;
|
|
}
|
|
|
|
static inline struct sched_entity *parent_entity(struct sched_entity *se)
|
|
{
|
|
return se->parent;
|
|
}
|
|
|
|
#else /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
#define for_each_sched_entity(se) \
|
|
for (; se; se = NULL)
|
|
|
|
static inline struct cfs_rq *task_cfs_rq(struct task_struct *p)
|
|
{
|
|
return &task_rq(p)->cfs;
|
|
}
|
|
|
|
static inline struct cfs_rq *cfs_rq_of(struct sched_entity *se)
|
|
{
|
|
struct task_struct *p = task_of(se);
|
|
struct rq *rq = task_rq(p);
|
|
|
|
return &rq->cfs;
|
|
}
|
|
|
|
/* runqueue "owned" by this group */
|
|
static inline struct cfs_rq *group_cfs_rq(struct sched_entity *grp)
|
|
{
|
|
return NULL;
|
|
}
|
|
|
|
static inline struct cfs_rq *cpu_cfs_rq(struct cfs_rq *cfs_rq, int this_cpu)
|
|
{
|
|
return &cpu_rq(this_cpu)->cfs;
|
|
}
|
|
|
|
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
|
|
for (cfs_rq = &rq->cfs; cfs_rq; cfs_rq = NULL)
|
|
|
|
static inline int
|
|
is_same_group(struct sched_entity *se, struct sched_entity *pse)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
static inline struct sched_entity *parent_entity(struct sched_entity *se)
|
|
{
|
|
return NULL;
|
|
}
|
|
|
|
#endif /* CONFIG_FAIR_GROUP_SCHED */
|
|
|
|
#ifdef CONFIG_SCHED_HRTICK
|
|
static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
int requeue = rq->curr == p;
|
|
struct sched_entity *se = &p->se;
|
|
struct cfs_rq *cfs_rq = cfs_rq_of(se);
|
|
|
|
WARN_ON(task_rq(p) != rq);
|
|
|
|
if (hrtick_enabled(rq) && cfs_rq->nr_running > 1) {
|
|
u64 slice = sched_slice(cfs_rq, se);
|
|
u64 ran = se->sum_exec_runtime - se->prev_sum_exec_runtime;
|
|
s64 delta = slice - ran;
|
|
|
|
if (delta < 0) {
|
|
if (rq->curr == p)
|
|
resched_task(p);
|
|
return;
|
|
}
|
|
|
|
/*
|
|
* Don't schedule slices shorter than 10000ns, that just
|
|
* doesn't make sense. Rely on vruntime for fairness.
|
|
*/
|
|
if (!requeue)
|
|
delta = max(10000LL, delta);
|
|
|
|
hrtick_start(rq, delta, requeue);
|
|
}
|
|
}
|
|
#else
|
|
static inline void
|
|
hrtick_start_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* The enqueue_task method is called before nr_running is
|
|
* increased. Here we update the fair scheduling stats and
|
|
* then put the task into the rbtree:
|
|
*/
|
|
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
if (se->on_rq)
|
|
break;
|
|
cfs_rq = cfs_rq_of(se);
|
|
enqueue_entity(cfs_rq, se, wakeup);
|
|
wakeup = 1;
|
|
}
|
|
|
|
hrtick_start_fair(rq, rq->curr);
|
|
}
|
|
|
|
/*
|
|
* The dequeue_task method is called before nr_running is
|
|
* decreased. We remove the task from the rbtree and
|
|
* update the fair scheduling stats:
|
|
*/
|
|
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &p->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
dequeue_entity(cfs_rq, se, sleep);
|
|
/* Don't dequeue parent if it has other entities besides us */
|
|
if (cfs_rq->load.weight)
|
|
break;
|
|
sleep = 1;
|
|
}
|
|
|
|
hrtick_start_fair(rq, rq->curr);
|
|
}
|
|
|
|
/*
|
|
* sched_yield() support is very simple - we dequeue and enqueue.
|
|
*
|
|
* If compat_yield is turned on then we requeue to the end of the tree.
|
|
*/
|
|
static void yield_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
struct sched_entity *rightmost, *se = &curr->se;
|
|
|
|
/*
|
|
* Are we the only task in the tree?
|
|
*/
|
|
if (unlikely(cfs_rq->nr_running == 1))
|
|
return;
|
|
|
|
if (likely(!sysctl_sched_compat_yield) && curr->policy != SCHED_BATCH) {
|
|
__update_rq_clock(rq);
|
|
/*
|
|
* Update run-time statistics of the 'current'.
|
|
*/
|
|
update_curr(cfs_rq);
|
|
|
|
return;
|
|
}
|
|
/*
|
|
* Find the rightmost entry in the rbtree:
|
|
*/
|
|
rightmost = __pick_last_entity(cfs_rq);
|
|
/*
|
|
* Already in the rightmost position?
|
|
*/
|
|
if (unlikely(rightmost->vruntime < se->vruntime))
|
|
return;
|
|
|
|
/*
|
|
* Minimally necessary key value to be last in the tree:
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
se->vruntime = rightmost->vruntime + 1;
|
|
}
|
|
|
|
/*
|
|
* wake_idle() will wake a task on an idle cpu if task->cpu is
|
|
* not idle and an idle cpu is available. The span of cpus to
|
|
* search starts with cpus closest then further out as needed,
|
|
* so we always favor a closer, idle cpu.
|
|
*
|
|
* Returns the CPU we should wake onto.
|
|
*/
|
|
#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
|
|
static int wake_idle(int cpu, struct task_struct *p)
|
|
{
|
|
cpumask_t tmp;
|
|
struct sched_domain *sd;
|
|
int i;
|
|
|
|
/*
|
|
* If it is idle, then it is the best cpu to run this task.
|
|
*
|
|
* This cpu is also the best, if it has more than one task already.
|
|
* Siblings must be also busy(in most cases) as they didn't already
|
|
* pickup the extra load from this cpu and hence we need not check
|
|
* sibling runqueue info. This will avoid the checks and cache miss
|
|
* penalities associated with that.
|
|
*/
|
|
if (idle_cpu(cpu) || cpu_rq(cpu)->nr_running > 1)
|
|
return cpu;
|
|
|
|
for_each_domain(cpu, sd) {
|
|
if (sd->flags & SD_WAKE_IDLE) {
|
|
cpus_and(tmp, sd->span, p->cpus_allowed);
|
|
for_each_cpu_mask(i, tmp) {
|
|
if (idle_cpu(i)) {
|
|
if (i != task_cpu(p)) {
|
|
schedstat_inc(p,
|
|
se.nr_wakeups_idle);
|
|
}
|
|
return i;
|
|
}
|
|
}
|
|
} else {
|
|
break;
|
|
}
|
|
}
|
|
return cpu;
|
|
}
|
|
#else
|
|
static inline int wake_idle(int cpu, struct task_struct *p)
|
|
{
|
|
return cpu;
|
|
}
|
|
#endif
|
|
|
|
#ifdef CONFIG_SMP
|
|
static int select_task_rq_fair(struct task_struct *p, int sync)
|
|
{
|
|
int cpu, this_cpu;
|
|
struct rq *rq;
|
|
struct sched_domain *sd, *this_sd = NULL;
|
|
int new_cpu;
|
|
|
|
cpu = task_cpu(p);
|
|
rq = task_rq(p);
|
|
this_cpu = smp_processor_id();
|
|
new_cpu = cpu;
|
|
|
|
if (cpu == this_cpu)
|
|
goto out_set_cpu;
|
|
|
|
for_each_domain(this_cpu, sd) {
|
|
if (cpu_isset(cpu, sd->span)) {
|
|
this_sd = sd;
|
|
break;
|
|
}
|
|
}
|
|
|
|
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
|
|
goto out_set_cpu;
|
|
|
|
/*
|
|
* Check for affine wakeup and passive balancing possibilities.
|
|
*/
|
|
if (this_sd) {
|
|
int idx = this_sd->wake_idx;
|
|
unsigned int imbalance;
|
|
unsigned long load, this_load;
|
|
|
|
imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
|
|
|
|
load = source_load(cpu, idx);
|
|
this_load = target_load(this_cpu, idx);
|
|
|
|
new_cpu = this_cpu; /* Wake to this CPU if we can */
|
|
|
|
if (this_sd->flags & SD_WAKE_AFFINE) {
|
|
unsigned long tl = this_load;
|
|
unsigned long tl_per_task;
|
|
|
|
/*
|
|
* Attract cache-cold tasks on sync wakeups:
|
|
*/
|
|
if (sync && !task_hot(p, rq->clock, this_sd))
|
|
goto out_set_cpu;
|
|
|
|
schedstat_inc(p, se.nr_wakeups_affine_attempts);
|
|
tl_per_task = cpu_avg_load_per_task(this_cpu);
|
|
|
|
/*
|
|
* If sync wakeup then subtract the (maximum possible)
|
|
* effect of the currently running task from the load
|
|
* of the current CPU:
|
|
*/
|
|
if (sync)
|
|
tl -= current->se.load.weight;
|
|
|
|
if ((tl <= load &&
|
|
tl + target_load(cpu, idx) <= tl_per_task) ||
|
|
100*(tl + p->se.load.weight) <= imbalance*load) {
|
|
/*
|
|
* This domain has SD_WAKE_AFFINE and
|
|
* p is cache cold in this domain, and
|
|
* there is no bad imbalance.
|
|
*/
|
|
schedstat_inc(this_sd, ttwu_move_affine);
|
|
schedstat_inc(p, se.nr_wakeups_affine);
|
|
goto out_set_cpu;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Start passive balancing when half the imbalance_pct
|
|
* limit is reached.
|
|
*/
|
|
if (this_sd->flags & SD_WAKE_BALANCE) {
|
|
if (imbalance*this_load <= 100*load) {
|
|
schedstat_inc(this_sd, ttwu_move_balance);
|
|
schedstat_inc(p, se.nr_wakeups_passive);
|
|
goto out_set_cpu;
|
|
}
|
|
}
|
|
}
|
|
|
|
new_cpu = cpu; /* Could not wake to this_cpu. Wake to cpu instead */
|
|
out_set_cpu:
|
|
return wake_idle(new_cpu, p);
|
|
}
|
|
#endif /* CONFIG_SMP */
|
|
|
|
|
|
/*
|
|
* Preempt the current task with a newly woken task if needed:
|
|
*/
|
|
static void check_preempt_wakeup(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct task_struct *curr = rq->curr;
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
|
|
struct sched_entity *se = &curr->se, *pse = &p->se;
|
|
unsigned long gran;
|
|
|
|
if (unlikely(rt_prio(p->prio))) {
|
|
update_rq_clock(rq);
|
|
update_curr(cfs_rq);
|
|
resched_task(curr);
|
|
return;
|
|
}
|
|
/*
|
|
* Batch tasks do not preempt (their preemption is driven by
|
|
* the tick):
|
|
*/
|
|
if (unlikely(p->policy == SCHED_BATCH))
|
|
return;
|
|
|
|
if (!sched_feat(WAKEUP_PREEMPT))
|
|
return;
|
|
|
|
while (!is_same_group(se, pse)) {
|
|
se = parent_entity(se);
|
|
pse = parent_entity(pse);
|
|
}
|
|
|
|
gran = sysctl_sched_wakeup_granularity;
|
|
/*
|
|
* More easily preempt - nice tasks, while not making
|
|
* it harder for + nice tasks.
|
|
*/
|
|
if (unlikely(se->load.weight > NICE_0_LOAD))
|
|
gran = calc_delta_fair(gran, &se->load);
|
|
|
|
if (pse->vruntime + gran < se->vruntime)
|
|
resched_task(curr);
|
|
}
|
|
|
|
static struct task_struct *pick_next_task_fair(struct rq *rq)
|
|
{
|
|
struct task_struct *p;
|
|
struct cfs_rq *cfs_rq = &rq->cfs;
|
|
struct sched_entity *se;
|
|
|
|
if (unlikely(!cfs_rq->nr_running))
|
|
return NULL;
|
|
|
|
do {
|
|
se = pick_next_entity(cfs_rq);
|
|
cfs_rq = group_cfs_rq(se);
|
|
} while (cfs_rq);
|
|
|
|
p = task_of(se);
|
|
hrtick_start_fair(rq, p);
|
|
|
|
return p;
|
|
}
|
|
|
|
/*
|
|
* Account for a descheduled task:
|
|
*/
|
|
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev)
|
|
{
|
|
struct sched_entity *se = &prev->se;
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
put_prev_entity(cfs_rq, se);
|
|
}
|
|
}
|
|
|
|
#ifdef CONFIG_SMP
|
|
/**************************************************
|
|
* Fair scheduling class load-balancing methods:
|
|
*/
|
|
|
|
/*
|
|
* Load-balancing iterator. Note: while the runqueue stays locked
|
|
* during the whole iteration, the current task might be
|
|
* dequeued so the iterator has to be dequeue-safe. Here we
|
|
* achieve that by always pre-iterating before returning
|
|
* the current task:
|
|
*/
|
|
static struct task_struct *
|
|
__load_balance_iterator(struct cfs_rq *cfs_rq, struct rb_node *curr)
|
|
{
|
|
struct task_struct *p;
|
|
|
|
if (!curr)
|
|
return NULL;
|
|
|
|
p = rb_entry(curr, struct task_struct, se.run_node);
|
|
cfs_rq->rb_load_balance_curr = rb_next(curr);
|
|
|
|
return p;
|
|
}
|
|
|
|
static struct task_struct *load_balance_start_fair(void *arg)
|
|
{
|
|
struct cfs_rq *cfs_rq = arg;
|
|
|
|
return __load_balance_iterator(cfs_rq, first_fair(cfs_rq));
|
|
}
|
|
|
|
static struct task_struct *load_balance_next_fair(void *arg)
|
|
{
|
|
struct cfs_rq *cfs_rq = arg;
|
|
|
|
return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
|
|
{
|
|
struct sched_entity *curr;
|
|
struct task_struct *p;
|
|
|
|
if (!cfs_rq->nr_running || !first_fair(cfs_rq))
|
|
return MAX_PRIO;
|
|
|
|
curr = cfs_rq->curr;
|
|
if (!curr)
|
|
curr = __pick_next_entity(cfs_rq);
|
|
|
|
p = task_of(curr);
|
|
|
|
return p->prio;
|
|
}
|
|
#endif
|
|
|
|
static unsigned long
|
|
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
unsigned long max_load_move,
|
|
struct sched_domain *sd, enum cpu_idle_type idle,
|
|
int *all_pinned, int *this_best_prio)
|
|
{
|
|
struct cfs_rq *busy_cfs_rq;
|
|
long rem_load_move = max_load_move;
|
|
struct rq_iterator cfs_rq_iterator;
|
|
|
|
cfs_rq_iterator.start = load_balance_start_fair;
|
|
cfs_rq_iterator.next = load_balance_next_fair;
|
|
|
|
for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
struct cfs_rq *this_cfs_rq;
|
|
long imbalance;
|
|
unsigned long maxload;
|
|
|
|
this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);
|
|
|
|
imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
|
|
/* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
|
|
if (imbalance <= 0)
|
|
continue;
|
|
|
|
/* Don't pull more than imbalance/2 */
|
|
imbalance /= 2;
|
|
maxload = min(rem_load_move, imbalance);
|
|
|
|
*this_best_prio = cfs_rq_best_prio(this_cfs_rq);
|
|
#else
|
|
# define maxload rem_load_move
|
|
#endif
|
|
/*
|
|
* pass busy_cfs_rq argument into
|
|
* load_balance_[start|next]_fair iterators
|
|
*/
|
|
cfs_rq_iterator.arg = busy_cfs_rq;
|
|
rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
|
|
maxload, sd, idle, all_pinned,
|
|
this_best_prio,
|
|
&cfs_rq_iterator);
|
|
|
|
if (rem_load_move <= 0)
|
|
break;
|
|
}
|
|
|
|
return max_load_move - rem_load_move;
|
|
}
|
|
|
|
static int
|
|
move_one_task_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
|
|
struct sched_domain *sd, enum cpu_idle_type idle)
|
|
{
|
|
struct cfs_rq *busy_cfs_rq;
|
|
struct rq_iterator cfs_rq_iterator;
|
|
|
|
cfs_rq_iterator.start = load_balance_start_fair;
|
|
cfs_rq_iterator.next = load_balance_next_fair;
|
|
|
|
for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
|
|
/*
|
|
* pass busy_cfs_rq argument into
|
|
* load_balance_[start|next]_fair iterators
|
|
*/
|
|
cfs_rq_iterator.arg = busy_cfs_rq;
|
|
if (iter_move_one_task(this_rq, this_cpu, busiest, sd, idle,
|
|
&cfs_rq_iterator))
|
|
return 1;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* scheduler tick hitting a task of our scheduling class:
|
|
*/
|
|
static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
struct sched_entity *se = &curr->se;
|
|
|
|
for_each_sched_entity(se) {
|
|
cfs_rq = cfs_rq_of(se);
|
|
entity_tick(cfs_rq, se, queued);
|
|
}
|
|
}
|
|
|
|
#define swap(a, b) do { typeof(a) tmp = (a); (a) = (b); (b) = tmp; } while (0)
|
|
|
|
/*
|
|
* Share the fairness runtime between parent and child, thus the
|
|
* total amount of pressure for CPU stays equal - new tasks
|
|
* get a chance to run but frequent forkers are not allowed to
|
|
* monopolize the CPU. Note: the parent runqueue is locked,
|
|
* the child is not running yet.
|
|
*/
|
|
static void task_new_fair(struct rq *rq, struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
struct sched_entity *se = &p->se, *curr = cfs_rq->curr;
|
|
int this_cpu = smp_processor_id();
|
|
|
|
sched_info_queued(p);
|
|
|
|
update_curr(cfs_rq);
|
|
place_entity(cfs_rq, se, 1);
|
|
|
|
/* 'curr' will be NULL if the child belongs to a different group */
|
|
if (sysctl_sched_child_runs_first && this_cpu == task_cpu(p) &&
|
|
curr && curr->vruntime < se->vruntime) {
|
|
/*
|
|
* Upon rescheduling, sched_class::put_prev_task() will place
|
|
* 'current' within the tree based on its new key value.
|
|
*/
|
|
swap(curr->vruntime, se->vruntime);
|
|
}
|
|
|
|
enqueue_task_fair(rq, p, 0);
|
|
resched_task(rq->curr);
|
|
}
|
|
|
|
/*
|
|
* Priority of the task has changed. Check to see if we preempt
|
|
* the current task.
|
|
*/
|
|
static void prio_changed_fair(struct rq *rq, struct task_struct *p,
|
|
int oldprio, int running)
|
|
{
|
|
/*
|
|
* Reschedule if we are currently running on this runqueue and
|
|
* our priority decreased, or if we are not currently running on
|
|
* this runqueue and our priority is higher than the current's
|
|
*/
|
|
if (running) {
|
|
if (p->prio > oldprio)
|
|
resched_task(rq->curr);
|
|
} else
|
|
check_preempt_curr(rq, p);
|
|
}
|
|
|
|
/*
|
|
* We switched to the sched_fair class.
|
|
*/
|
|
static void switched_to_fair(struct rq *rq, struct task_struct *p,
|
|
int running)
|
|
{
|
|
/*
|
|
* We were most likely switched from sched_rt, so
|
|
* kick off the schedule if running, otherwise just see
|
|
* if we can still preempt the current task.
|
|
*/
|
|
if (running)
|
|
resched_task(rq->curr);
|
|
else
|
|
check_preempt_curr(rq, p);
|
|
}
|
|
|
|
/* Account for a task changing its policy or group.
|
|
*
|
|
* This routine is mostly called to set cfs_rq->curr field when a task
|
|
* migrates between groups/classes.
|
|
*/
|
|
static void set_curr_task_fair(struct rq *rq)
|
|
{
|
|
struct sched_entity *se = &rq->curr->se;
|
|
|
|
for_each_sched_entity(se)
|
|
set_next_entity(cfs_rq_of(se), se);
|
|
}
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
static void moved_group_fair(struct task_struct *p)
|
|
{
|
|
struct cfs_rq *cfs_rq = task_cfs_rq(p);
|
|
|
|
update_curr(cfs_rq);
|
|
place_entity(cfs_rq, &p->se, 1);
|
|
}
|
|
#endif
|
|
|
|
/*
|
|
* All the scheduling class methods:
|
|
*/
|
|
static const struct sched_class fair_sched_class = {
|
|
.next = &idle_sched_class,
|
|
.enqueue_task = enqueue_task_fair,
|
|
.dequeue_task = dequeue_task_fair,
|
|
.yield_task = yield_task_fair,
|
|
#ifdef CONFIG_SMP
|
|
.select_task_rq = select_task_rq_fair,
|
|
#endif /* CONFIG_SMP */
|
|
|
|
.check_preempt_curr = check_preempt_wakeup,
|
|
|
|
.pick_next_task = pick_next_task_fair,
|
|
.put_prev_task = put_prev_task_fair,
|
|
|
|
#ifdef CONFIG_SMP
|
|
.load_balance = load_balance_fair,
|
|
.move_one_task = move_one_task_fair,
|
|
#endif
|
|
|
|
.set_curr_task = set_curr_task_fair,
|
|
.task_tick = task_tick_fair,
|
|
.task_new = task_new_fair,
|
|
|
|
.prio_changed = prio_changed_fair,
|
|
.switched_to = switched_to_fair,
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
.moved_group = moved_group_fair,
|
|
#endif
|
|
};
|
|
|
|
#ifdef CONFIG_SCHED_DEBUG
|
|
static void print_cfs_stats(struct seq_file *m, int cpu)
|
|
{
|
|
struct cfs_rq *cfs_rq;
|
|
|
|
#ifdef CONFIG_FAIR_GROUP_SCHED
|
|
print_cfs_rq(m, cpu, &cpu_rq(cpu)->cfs);
|
|
#endif
|
|
rcu_read_lock();
|
|
for_each_leaf_cfs_rq(cpu_rq(cpu), cfs_rq)
|
|
print_cfs_rq(m, cpu, cfs_rq);
|
|
rcu_read_unlock();
|
|
}
|
|
#endif
|