/*
* Completely Fair Scheduling (CFS) Class (SCHED_NORMAL/SCHED_BATCH)
*
* Copyright (C) 2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
*
* Interactivity improvements by Mike Galbraith
* (C) 2007 Mike Galbraith <efault@gmx.de>
*
* Various enhancements by Dmitry Adamushko.
* (C) 2007 Dmitry Adamushko <dmitry.adamushko@gmail.com>
*
* Group scheduling enhancements by Srivatsa Vaddagiri
* Copyright IBM Corporation, 2007
* Author: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
*
* Scaled math optimizations by Thomas Gleixner
* Copyright (C) 2007, Thomas Gleixner <tglx@linutronix.de>
*/
/*
* Preemption granularity:
* (default: 2 msec, units: nanoseconds)
*
* NOTE: this granularity value is not the same as the concept of
* 'timeslice length' - timeslices in CFS will typically be somewhat
* larger than this value. (to see the precise effective timeslice
* length of your workload, run vmstat and monitor the context-switches
* field)
*
* On SMP systems the value of this is multiplied by the log2 of the
* number of CPUs. (i.e. factor 2x on 2-way systems, 3x on 4-way
* systems, 4x on 8-way systems, 5x on 16-way systems, etc.)
*/
unsigned int sysctl_sched_granularity __read_mostly = 2000000000ULL/HZ;
/*
* SCHED_BATCH wake-up granularity.
* (default: 10 msec, units: nanoseconds)
*
* This option delays the preemption effects of decoupled workloads
* and reduces their over-scheduling. Synchronous workloads will still
* have immediate wakeup/sleep latencies.
*/
unsigned int sysctl_sched_batch_wakeup_granularity __read_mostly =
10000000000ULL/HZ;
/*
* SCHED_OTHER wake-up granularity.
* (default: 1 msec, units: nanoseconds)
*
* This option delays the preemption effects of decoupled workloads
* and reduces their over-scheduling. Synchronous workloads will still
* have immediate wakeup/sleep latencies.
*/
unsigned int sysctl_sched_wakeup_granularity __read_mostly = 1000000000ULL/HZ;
unsigned int sysctl_sched_stat_granularity __read_mostly;
/*
* Initialized in sched_init_granularity():
*/
unsigned int sysctl_sched_runtime_limit __read_mostly;
/*
* Debugging: various feature bits
*/
enum {
SCHED_FEAT_FAIR_SLEEPERS = 1,
SCHED_FEAT_SLEEPER_AVG = 2,
SCHED_FEAT_SLEEPER_LOAD_AVG = 4,
SCHED_FEAT_PRECISE_CPU_LOAD = 8,
SCHED_FEAT_START_DEBIT = 16,
SCHED_FEAT_SKIP_INITIAL = 32,
};
unsigned int sysctl_sched_features __read_mostly =
SCHED_FEAT_FAIR_SLEEPERS *1 |
SCHED_FEAT_SLEEPER_AVG *1 |
SCHED_FEAT_SLEEPER_LOAD_AVG *1 |
SCHED_FEAT_PRECISE_CPU_LOAD *1 |
SCHED_FEAT_START_DEBIT *1 |
SCHED_FEAT_SKIP_INITIAL *0;
extern struct sched_class fair_sched_class;
/**************************************************************
* CFS operations on generic schedulable entities:
*/
#ifdef CONFIG_FAIR_GROUP_SCHED
/* cpu runqueue to which this cfs_rq is attached */
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
return cfs_rq->rq;
}
/* currently running entity (if any) on this cfs_rq */
static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
{
return cfs_rq->curr;
}
/* An entity is a task if it doesn't "own" a runqueue */
#define entity_is_task(se) (!se->my_q)
static inline void
set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
cfs_rq->curr = se;
}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
{
return container_of(cfs_rq, struct rq, cfs);
}
static inline struct sched_entity *cfs_rq_curr(struct cfs_rq *cfs_rq)
{
struct rq *rq = rq_of(cfs_rq);
if (unlikely(rq->curr->sched_class != &fair_sched_class))
return NULL;
return &rq->curr->se;
}
#define entity_is_task(se) 1
static inline void
set_cfs_rq_curr(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif /* CONFIG_FAIR_GROUP_SCHED */
static inline struct task_struct *task_of(struct sched_entity *se)
{
return container_of(se, struct task_struct, se);
}
/**************************************************************
* Scheduling class tree data structure manipulation methods:
*/
/*
* Enqueue an entity into the rb-tree:
*/
static inline void
__enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
struct rb_node **link = &cfs_rq->tasks_timeline.rb_node;
struct rb_node *parent = NULL;
struct sched_entity *entry;
s64 key = se->fair_key;
int leftmost = 1;
/*
* Find the right place in the rbtree:
*/
while (*link) {
parent = *link;
entry = rb_entry(parent, struct sched_entity, run_node);
/*
* We dont care about collisions. Nodes with
* the same key stay together.
*/
if (key - entry->fair_key < 0) {
link = &parent->rb_left;
} else {
link = &parent->rb_right;
leftmost = 0;
}
}
/*
* Maintain a cache of leftmost tree entries (it is frequently
* used):
*/
if (leftmost)
cfs_rq->rb_leftmost = &se->run_node;
rb_link_node(&se->run_node, parent, link);
rb_insert_color(&se->run_node, &cfs_rq->tasks_timeline);
update_load_add(&cfs_rq->load, se->load.weight);
cfs_rq->nr_running++;
se->on_rq = 1;
}
static inline void
__dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
if (cfs_rq->rb_leftmost == &se->run_node)
cfs_rq->rb_leftmost = rb_next(&se->run_node);
rb_erase(&se->run_node, &cfs_rq->tasks_timeline);
update_load_sub(&cfs_rq->load, se->load.weight);
cfs_rq->nr_running--;
se->on_rq = 0;
}
static inline struct rb_node *first_fair(struct cfs_rq *cfs_rq)
{
return cfs_rq->rb_leftmost;
}
static struct sched_entity *__pick_next_entity(struct cfs_rq *cfs_rq)
{
return rb_entry(first_fair(cfs_rq), struct sched_entity, run_node);
}
/**************************************************************
* Scheduling class statistics methods:
*/
/*
* We rescale the rescheduling granularity of tasks according to their
* nice level, but only linearly, not exponentially:
*/
static long
niced_granularity(struct sched_entity *curr, unsigned long granularity)
{
u64 tmp;
/*
* Negative nice levels get the same granularity as nice-0:
*/
if (likely(curr->load.weight >= NICE_0_LOAD))
return granularity;
/*
* Positive nice level tasks get linearly finer
* granularity:
*/
tmp = curr->load.weight * (u64)granularity;
/*
* It will always fit into 'long':
*/
return (long) (tmp >> NICE_0_SHIFT);
}
static inline void
limit_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
long limit = sysctl_sched_runtime_limit;
/*
* Niced tasks have the same history dynamic range as
* non-niced tasks:
*/
if (unlikely(se->wait_runtime > limit)) {
se->wait_runtime = limit;
schedstat_inc(se, wait_runtime_overruns);
schedstat_inc(cfs_rq, wait_runtime_overruns);
}
if (unlikely(se->wait_runtime < -limit)) {
se->wait_runtime = -limit;
schedstat_inc(se, wait_runtime_underruns);
schedstat_inc(cfs_rq, wait_runtime_underruns);
}
}
static inline void
__add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
{
se->wait_runtime += delta;
schedstat_add(se, sum_wait_runtime, delta);
limit_wait_runtime(cfs_rq, se);
}
static void
add_wait_runtime(struct cfs_rq *cfs_rq, struct sched_entity *se, long delta)
{
schedstat_add(cfs_rq, wait_runtime, -se->wait_runtime);
__add_wait_runtime(cfs_rq, se, delta);
schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
}
/*
* Update the current task's runtime statistics. Skip current tasks that
* are not in our scheduling class.
*/
static inline void
__update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
unsigned long delta, delta_exec, delta_fair, delta_mine;
struct load_weight *lw = &cfs_rq->load;
unsigned long load = lw->weight;
delta_exec = curr->delta_exec;
schedstat_set(curr->exec_max, max((u64)delta_exec, curr->exec_max));
curr->sum_exec_runtime += delta_exec;
cfs_rq->exec_clock += delta_exec;
if (unlikely(!load))
return;
delta_fair = calc_delta_fair(delta_exec, lw);
delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
if (cfs_rq->sleeper_bonus > sysctl_sched_granularity) {
delta = calc_delta_mine(cfs_rq->sleeper_bonus,
curr->load.weight, lw);
if (unlikely(delta > cfs_rq->sleeper_bonus))
delta = cfs_rq->sleeper_bonus;
cfs_rq->sleeper_bonus -= delta;
delta_mine -= delta;
}
cfs_rq->fair_clock += delta_fair;
/*
* We executed delta_exec amount of time on the CPU,
* but we were only entitled to delta_mine amount of
* time during that period (if nr_running == 1 then
* the two values are equal)
* [Note: delta_mine - delta_exec is negative]:
*/
add_wait_runtime(cfs_rq, curr, delta_mine - delta_exec);
}
static void update_curr(struct cfs_rq *cfs_rq)
{
struct sched_entity *curr = cfs_rq_curr(cfs_rq);
unsigned long delta_exec;
if (unlikely(!curr))
return;
/*
* Get the amount of time the current task was running
* since the last time we changed load (this cannot
* overflow on 32 bits):
*/
delta_exec = (unsigned long)(rq_of(cfs_rq)->clock - curr->exec_start);
curr->delta_exec += delta_exec;
if (unlikely(curr->delta_exec > sysctl_sched_stat_granularity)) {
__update_curr(cfs_rq, curr);
curr->delta_exec = 0;
}
curr->exec_start = rq_of(cfs_rq)->clock;
}
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
se->wait_start_fair = cfs_rq->fair_clock;
schedstat_set(se->wait_start, rq_of(cfs_rq)->clock);
}
/*
* We calculate fair deltas here, so protect against the random effects
* of a multiplication overflow by capping it to the runtime limit:
*/
#if BITS_PER_LONG == 32
static inline unsigned long
calc_weighted(unsigned long delta, unsigned long weight, int shift)
{
u64 tmp = (u64)delta * weight >> shift;
if (unlikely(tmp > sysctl_sched_runtime_limit*2))
return sysctl_sched_runtime_limit*2;
return tmp;
}
#else
static inline unsigned long
calc_weighted(unsigned long delta, unsigned long weight, int shift)
{
return delta * weight >> shift;
}
#endif
/*
* Task is being enqueued - update stats:
*/
static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
s64 key;
/*
* Are we enqueueing a waiting task? (for current tasks
* a dequeue/enqueue event is a NOP)
*/
if (se != cfs_rq_curr(cfs_rq))
update_stats_wait_start(cfs_rq, se);
/*
* Update the key:
*/
key = cfs_rq->fair_clock;
/*
* Optimize the common nice 0 case:
*/
if (likely(se->load.weight == NICE_0_LOAD)) {
key -= se->wait_runtime;
} else {
u64 tmp;
if (se->wait_runtime < 0) {
tmp = -se->wait_runtime;
key += (tmp * se->load.inv_weight) >>
(WMULT_SHIFT - NICE_0_SHIFT);
} else {
tmp = se->wait_runtime;
key -= (tmp * se->load.weight) >> NICE_0_SHIFT;
}
}
se->fair_key = key;
}
/*
* Note: must be called with a freshly updated rq->fair_clock.
*/
static inline void
__update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned long delta_fair = se->delta_fair_run;
schedstat_set(se->wait_max, max(se->wait_max,
rq_of(cfs_rq)->clock - se->wait_start));
if (unlikely(se->load.weight != NICE_0_LOAD))
delta_fair = calc_weighted(delta_fair, se->load.weight,
NICE_0_SHIFT);
add_wait_runtime(cfs_rq, se, delta_fair);
}
static void
update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned long delta_fair;
delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
(u64)(cfs_rq->fair_clock - se->wait_start_fair));
se->delta_fair_run += delta_fair;
if (unlikely(abs(se->delta_fair_run) >=
sysctl_sched_stat_granularity)) {
__update_stats_wait_end(cfs_rq, se);
se->delta_fair_run = 0;
}
se->wait_start_fair = 0;
schedstat_set(se->wait_start, 0);
}
static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
update_curr(cfs_rq);
/*
* Mark the end of the wait period if dequeueing a
* waiting task:
*/
if (se != cfs_rq_curr(cfs_rq))
update_stats_wait_end(cfs_rq, se);
}
/*
* We are picking a new current task - update its stats:
*/
static inline void
update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
/*
* We are starting a new run period:
*/
se->exec_start = rq_of(cfs_rq)->clock;
}
/*
* We are descheduling a task - update its stats:
*/
static inline void
update_stats_curr_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
se->exec_start = 0;
}
/**************************************************
* Scheduling class queueing methods:
*/
static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
unsigned long load = cfs_rq->load.weight, delta_fair;
long prev_runtime;
if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG)
load = rq_of(cfs_rq)->cpu_load[2];
delta_fair = se->delta_fair_sleep;
/*
* Fix up delta_fair with the effect of us running
* during the whole sleep period:
*/
if (sysctl_sched_features & SCHED_FEAT_SLEEPER_AVG)
delta_fair = div64_likely32((u64)delta_fair * load,
load + se->load.weight);
if (unlikely(se->load.weight != NICE_0_LOAD))
delta_fair = calc_weighted(delta_fair, se->load.weight,
NICE_0_SHIFT);
prev_runtime = se->wait_runtime;
__add_wait_runtime(cfs_rq, se, delta_fair);
delta_fair = se->wait_runtime - prev_runtime;
/*
* Track the amount of bonus we've given to sleepers:
*/
cfs_rq->sleeper_bonus += delta_fair;
schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
}
static void
enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
{
struct task_struct *tsk = task_of(se);
unsigned long delta_fair;
if ((entity_is_task(se) && tsk->policy == SCHED_BATCH) ||
!(sysctl_sched_features & SCHED_FEAT_FAIR_SLEEPERS))
return;
delta_fair = (unsigned long)min((u64)(2*sysctl_sched_runtime_limit),
(u64)(cfs_rq->fair_clock - se->sleep_start_fair));
se->delta_fair_sleep += delta_fair;
if (unlikely(abs(se->delta_fair_sleep) >=
sysctl_sched_stat_granularity)) {
__enqueue_sleeper(cfs_rq, se);
se->delta_fair_sleep = 0;
}
se->sleep_start_fair = 0;
#ifdef CONFIG_SCHEDSTATS
if (se->sleep_start) {
u64 delta = rq_of(cfs_rq)->clock - se->sleep_start;
if ((s64)delta < 0)
delta = 0;
if (unlikely(delta > se->sleep_max))
se->sleep_max = delta;
se->sleep_start = 0;
se->sum_sleep_runtime += delta;
}
if (se->block_start) {
u64 delta = rq_of(cfs_rq)->clock - se->block_start;
if ((s64)delta < 0)
delta = 0;
if (unlikely(delta > se->block_max))
se->block_max = delta;
se->block_start = 0;
se->sum_sleep_runtime += delta;
}
#endif
}
static void
enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
int wakeup, u64 now)
{
/*
* Update the fair clock.
*/
update_curr(cfs_rq);
if (wakeup)
enqueue_sleeper(cfs_rq, se, now);
update_stats_enqueue(cfs_rq, se);
__enqueue_entity(cfs_rq, se);
}
static void
dequeue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
int sleep, u64 now)
{
update_stats_dequeue(cfs_rq, se);
if (sleep) {
se->sleep_start_fair = cfs_rq->fair_clock;
#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;
}
cfs_rq->wait_runtime -= se->wait_runtime;
#endif
}
__dequeue_entity(cfs_rq, se);
}
/*
* Preempt the current task with a newly woken task if needed:
*/
static void
__check_preempt_curr_fair(struct cfs_rq *cfs_rq, struct sched_entity *se,
struct sched_entity *curr, unsigned long granularity)
{
s64 __delta = curr->fair_key - se->fair_key;
/*
* Take scheduling granularity into account - do not
* preempt the current task unless the best task has
* a larger than sched_granularity fairness advantage:
*/
if (__delta > niced_granularity(curr, granularity))
resched_task(rq_of(cfs_rq)->curr);
}
static inline void
set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, u64 now)
{
/*
* 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. (note, here we rely on pick_next_task() having
* done a put_prev_task_fair() shortly before this, which
* updated rq->fair_clock - used by update_stats_wait_end())
*/
update_stats_wait_end(cfs_rq, se);
update_stats_curr_start(cfs_rq, se);
set_cfs_rq_curr(cfs_rq, se);
}
static struct sched_entity *pick_next_entity(struct cfs_rq *cfs_rq, u64 now)
{
struct sched_entity *se = __pick_next_entity(cfs_rq);
set_next_entity(cfs_rq, se, now);
return se;
}
static void
put_prev_entity(struct cfs_rq *cfs_rq, struct sched_entity *prev, u64 now)
{
/*
* 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);
update_stats_curr_end(cfs_rq, prev);
if (prev->on_rq)
update_stats_wait_start(cfs_rq, prev);
set_cfs_rq_curr(cfs_rq, NULL);
}
static void entity_tick(struct cfs_rq *cfs_rq, struct sched_entity *curr)
{
struct rq *rq = rq_of(cfs_rq);
struct sched_entity *next;
u64 now;
__update_rq_clock(rq);
now = rq->clock;
/*
* Dequeue and enqueue the task to update its
* position within the tree:
*/
dequeue_entity(cfs_rq, curr, 0, now);
enqueue_entity(cfs_rq, curr, 0, now);
/*
* Reschedule if another task tops the current one.
*/
next = __pick_next_entity(cfs_rq);
if (next == curr)
return;
__check_preempt_curr_fair(cfs_rq, next, curr, sysctl_sched_granularity);
}
/**************************************************
* 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)
{
/* A later patch will take group into account */
return &cpu_rq(this_cpu)->cfs;
}
/* Iterate thr' all leaf cfs_rq's on a runqueue */
#define for_each_leaf_cfs_rq(rq, cfs_rq) \
list_for_each_entry(cfs_rq, &rq->leaf_cfs_rq_list, leaf_cfs_rq_list)
/* Do the two (enqueued) tasks belong to the same group ? */
static inline int is_same_group(struct task_struct *curr, struct task_struct *p)
{
if (curr->se.cfs_rq == p->se.cfs_rq)
return 1;
return 0;
}
#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 task_struct *curr, struct task_struct *p)
{
return 1;
}
#endif /* CONFIG_FAIR_GROUP_SCHED */
/*
* 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, u64 now)
{
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, now);
}
}
/*
* 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, u64 now)
{
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, now);
/* Don't dequeue parent if it has other entities besides us */
if (cfs_rq->load.weight)
break;
}
}
/*
* sched_yield() support is very simple - we dequeue and enqueue
*/
static void yield_task_fair(struct rq *rq, struct task_struct *p)
{
struct cfs_rq *cfs_rq = task_cfs_rq(p);
u64 now;
__update_rq_clock(rq);
now = rq->clock;
/*
* Dequeue and enqueue the task to update its
* position within the tree:
*/
dequeue_entity(cfs_rq, &p->se, 0, now);
enqueue_entity(cfs_rq, &p->se, 0, now);
}
/*
* Preempt the current task with a newly woken task if needed:
*/
static void check_preempt_curr_fair(struct rq *rq, struct task_struct *p)
{
struct task_struct *curr = rq->curr;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
unsigned long gran;
if (unlikely(rt_prio(p->prio))) {
update_rq_clock(rq);
update_curr(cfs_rq);
resched_task(curr);
return;
}
gran = sysctl_sched_wakeup_granularity;
/*
* Batch tasks prefer throughput over latency:
*/
if (unlikely(p->policy == SCHED_BATCH))
gran = sysctl_sched_batch_wakeup_granularity;
if (is_same_group(curr, p))
__check_preempt_curr_fair(cfs_rq, &p->se, &curr->se, gran);
}
static struct task_struct *pick_next_task_fair(struct rq *rq, u64 now)
{
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, now);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);
return task_of(se);
}
/*
* Account for a descheduled task:
*/
static void put_prev_task_fair(struct rq *rq, struct task_struct *prev, u64 now)
{
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, now);
}
}
/**************************************************
* 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 inline 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)
return MAX_PRIO;
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_nr_move, 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;
unsigned long load_moved, total_nr_moved = 0, nr_moved;
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 imbalances;
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;
nr_moved = balance_tasks(this_rq, this_cpu, busiest,
max_nr_move, maxload, sd, idle, all_pinned,
&load_moved, this_best_prio, &cfs_rq_iterator);
total_nr_moved += nr_moved;
max_nr_move -= nr_moved;
rem_load_move -= load_moved;
if (max_nr_move <= 0 || rem_load_move <= 0)
break;
}
return max_load_move - rem_load_move;
}
/*
* scheduler tick hitting a task of our scheduling class:
*/
static void task_tick_fair(struct rq *rq, struct task_struct *curr)
{
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);
}
}
/*
* 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, u64 now)
{
struct cfs_rq *cfs_rq = task_cfs_rq(p);
struct sched_entity *se = &p->se;
sched_info_queued(p);
update_stats_enqueue(cfs_rq, se);
/*
* Child runs first: we let it run before the parent
* until it reschedules once. We set up the key so that
* it will preempt the parent:
*/
p->se.fair_key = current->se.fair_key -
niced_granularity(&rq->curr->se, sysctl_sched_granularity) - 1;
/*
* The first wait is dominated by the child-runs-first logic,
* so do not credit it with that waiting time yet:
*/
if (sysctl_sched_features & SCHED_FEAT_SKIP_INITIAL)
p->se.wait_start_fair = 0;
/*
* The statistical average of wait_runtime is about
* -granularity/2, so initialize the task with that:
*/
if (sysctl_sched_features & SCHED_FEAT_START_DEBIT)
p->se.wait_runtime = -(sysctl_sched_granularity / 2);
__enqueue_entity(cfs_rq, se);
}
#ifdef CONFIG_FAIR_GROUP_SCHED
/* 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 task_struct *curr = rq->curr;
struct sched_entity *se = &curr->se;
u64 now;
struct cfs_rq *cfs_rq;
update_rq_clock(rq);
now = rq->clock;
for_each_sched_entity(se) {
cfs_rq = cfs_rq_of(se);
set_next_entity(cfs_rq, se, now);
}
}
#else
static void set_curr_task_fair(struct rq *rq)
{
}
#endif
/*
* All the scheduling class methods:
*/
struct sched_class fair_sched_class __read_mostly = {
.enqueue_task = enqueue_task_fair,
.dequeue_task = dequeue_task_fair,
.yield_task = yield_task_fair,
.check_preempt_curr = check_preempt_curr_fair,
.pick_next_task = pick_next_task_fair,
.put_prev_task = put_prev_task_fair,
.load_balance = load_balance_fair,
.set_curr_task = set_curr_task_fair,
.task_tick = task_tick_fair,
.task_new = task_new_fair,
};
#ifdef CONFIG_SCHED_DEBUG
static void print_cfs_stats(struct seq_file *m, int cpu)
{
struct rq *rq = cpu_rq(cpu);
struct cfs_rq *cfs_rq;
for_each_leaf_cfs_rq(rq, cfs_rq)
print_cfs_rq(m, cpu, cfs_rq);
}
#endif
