#include <asm/irq_regs.h>
#include "sched_cpupri.h"
+#include "workqueue_sched.h"
#define CREATE_TRACE_POINTS
#include <trace/events/sched.h>
unsigned long nr_running;
#define CPU_LOAD_IDX_MAX 5
unsigned long cpu_load[CPU_LOAD_IDX_MAX];
+ unsigned long last_load_update_tick;
#ifdef CONFIG_NO_HZ
u64 nohz_stamp;
- unsigned char in_nohz_recently;
+ unsigned char nohz_balance_kick;
#endif
unsigned int skip_clock_update;
}
#ifdef CONFIG_NO_HZ
+/*
+ * In the semi idle case, use the nearest busy cpu for migrating timers
+ * from an idle cpu. This is good for power-savings.
+ *
+ * We don't do similar optimization for completely idle system, as
+ * selecting an idle cpu will add more delays to the timers than intended
+ * (as that cpu's timer base may not be uptodate wrt jiffies etc).
+ */
+int get_nohz_timer_target(void)
+{
+ int cpu = smp_processor_id();
+ int i;
+ struct sched_domain *sd;
+
+ for_each_domain(cpu, sd) {
+ for_each_cpu(i, sched_domain_span(sd))
+ if (!idle_cpu(i))
+ return i;
+ }
+ return cpu;
+}
/*
* When add_timer_on() enqueues a timer into the timer wheel of an
* idle CPU then this timer might expire before the next timer event
if (root_task_group_empty())
return;
- now = cpu_clock(raw_smp_processor_id());
+ now = local_clock();
elapsed = now - sd->last_update;
if (elapsed >= (s64)(u64)sysctl_sched_shares_ratelimit) {
static void calc_load_account_idle(struct rq *this_rq);
static void update_sysctl(void);
static int get_update_sysctl_factor(void);
+static void update_cpu_load(struct rq *this_rq);
static inline void __set_task_cpu(struct task_struct *p, unsigned int cpu)
{
}
#endif
-/***
+static inline void ttwu_activate(struct task_struct *p, struct rq *rq,
+ bool is_sync, bool is_migrate, bool is_local,
+ unsigned long en_flags)
+{
+ schedstat_inc(p, se.statistics.nr_wakeups);
+ if (is_sync)
+ schedstat_inc(p, se.statistics.nr_wakeups_sync);
+ if (is_migrate)
+ schedstat_inc(p, se.statistics.nr_wakeups_migrate);
+ if (is_local)
+ schedstat_inc(p, se.statistics.nr_wakeups_local);
+ else
+ schedstat_inc(p, se.statistics.nr_wakeups_remote);
+
+ activate_task(rq, p, en_flags);
+}
+
+static inline void ttwu_post_activation(struct task_struct *p, struct rq *rq,
+ int wake_flags, bool success)
+{
+ trace_sched_wakeup(p, success);
+ check_preempt_curr(rq, p, wake_flags);
+
+ p->state = TASK_RUNNING;
+#ifdef CONFIG_SMP
+ if (p->sched_class->task_woken)
+ p->sched_class->task_woken(rq, p);
+
+ if (unlikely(rq->idle_stamp)) {
+ u64 delta = rq->clock - rq->idle_stamp;
+ u64 max = 2*sysctl_sched_migration_cost;
+
+ if (delta > max)
+ rq->avg_idle = max;
+ else
+ update_avg(&rq->avg_idle, delta);
+ rq->idle_stamp = 0;
+ }
+#endif
+ /* if a worker is waking up, notify workqueue */
+ if ((p->flags & PF_WQ_WORKER) && success)
+ wq_worker_waking_up(p, cpu_of(rq));
+}
+
+/**
* try_to_wake_up - wake up a thread
- * @p: the to-be-woken-up thread
+ * @p: the thread to be awakened
* @state: the mask of task states that can be woken
- * @sync: do a synchronous wakeup?
+ * @wake_flags: wake modifier flags (WF_*)
*
* Put it on the run-queue if it's not already there. The "current"
* thread is always on the run-queue (except when the actual
* the simpler "current->state = TASK_RUNNING" to mark yourself
* runnable without the overhead of this.
*
- * returns failure only if the task is already active.
+ * Returns %true if @p was woken up, %false if it was already running
+ * or @state didn't match @p's state.
*/
static int try_to_wake_up(struct task_struct *p, unsigned int state,
int wake_flags)
out_activate:
#endif /* CONFIG_SMP */
- schedstat_inc(p, se.statistics.nr_wakeups);
- if (wake_flags & WF_SYNC)
- schedstat_inc(p, se.statistics.nr_wakeups_sync);
- if (orig_cpu != cpu)
- schedstat_inc(p, se.statistics.nr_wakeups_migrate);
- if (cpu == this_cpu)
- schedstat_inc(p, se.statistics.nr_wakeups_local);
- else
- schedstat_inc(p, se.statistics.nr_wakeups_remote);
- activate_task(rq, p, en_flags);
+ ttwu_activate(p, rq, wake_flags & WF_SYNC, orig_cpu != cpu,
+ cpu == this_cpu, en_flags);
success = 1;
-
out_running:
- trace_sched_wakeup(p, success);
- check_preempt_curr(rq, p, wake_flags);
-
- p->state = TASK_RUNNING;
-#ifdef CONFIG_SMP
- if (p->sched_class->task_woken)
- p->sched_class->task_woken(rq, p);
-
- if (unlikely(rq->idle_stamp)) {
- u64 delta = rq->clock - rq->idle_stamp;
- u64 max = 2*sysctl_sched_migration_cost;
-
- if (delta > max)
- rq->avg_idle = max;
- else
- update_avg(&rq->avg_idle, delta);
- rq->idle_stamp = 0;
- }
-#endif
+ ttwu_post_activation(p, rq, wake_flags, success);
out:
task_rq_unlock(rq, &flags);
put_cpu();
return success;
}
+/**
+ * try_to_wake_up_local - try to wake up a local task with rq lock held
+ * @p: the thread to be awakened
+ *
+ * Put @p on the run-queue if it's not alredy there. The caller must
+ * ensure that this_rq() is locked, @p is bound to this_rq() and not
+ * the current task. this_rq() stays locked over invocation.
+ */
+static void try_to_wake_up_local(struct task_struct *p)
+{
+ struct rq *rq = task_rq(p);
+ bool success = false;
+
+ BUG_ON(rq != this_rq());
+ BUG_ON(p == current);
+ lockdep_assert_held(&rq->lock);
+
+ if (!(p->state & TASK_NORMAL))
+ return;
+
+ if (!p->se.on_rq) {
+ if (likely(!task_running(rq, p))) {
+ schedstat_inc(rq, ttwu_count);
+ schedstat_inc(rq, ttwu_local);
+ }
+ ttwu_activate(p, rq, false, false, true, ENQUEUE_WAKEUP);
+ success = true;
+ }
+ ttwu_post_activation(p, rq, 0, success);
+}
+
/**
* wake_up_process - Wake up a specific process
* @p: The process to be woken up.
this_rq->calc_load_update += LOAD_FREQ;
}
+/*
+ * The exact cpuload at various idx values, calculated at every tick would be
+ * load = (2^idx - 1) / 2^idx * load + 1 / 2^idx * cur_load
+ *
+ * If a cpu misses updates for n-1 ticks (as it was idle) and update gets called
+ * on nth tick when cpu may be busy, then we have:
+ * load = ((2^idx - 1) / 2^idx)^(n-1) * load
+ * load = (2^idx - 1) / 2^idx) * load + 1 / 2^idx * cur_load
+ *
+ * decay_load_missed() below does efficient calculation of
+ * load = ((2^idx - 1) / 2^idx)^(n-1) * load
+ * avoiding 0..n-1 loop doing load = ((2^idx - 1) / 2^idx) * load
+ *
+ * The calculation is approximated on a 128 point scale.
+ * degrade_zero_ticks is the number of ticks after which load at any
+ * particular idx is approximated to be zero.
+ * degrade_factor is a precomputed table, a row for each load idx.
+ * Each column corresponds to degradation factor for a power of two ticks,
+ * based on 128 point scale.
+ * Example:
+ * row 2, col 3 (=12) says that the degradation at load idx 2 after
+ * 8 ticks is 12/128 (which is an approximation of exact factor 3^8/4^8).
+ *
+ * With this power of 2 load factors, we can degrade the load n times
+ * by looking at 1 bits in n and doing as many mult/shift instead of
+ * n mult/shifts needed by the exact degradation.
+ */
+#define DEGRADE_SHIFT 7
+static const unsigned char
+ degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
+static const unsigned char
+ degrade_factor[CPU_LOAD_IDX_MAX][DEGRADE_SHIFT + 1] = {
+ {0, 0, 0, 0, 0, 0, 0, 0},
+ {64, 32, 8, 0, 0, 0, 0, 0},
+ {96, 72, 40, 12, 1, 0, 0},
+ {112, 98, 75, 43, 15, 1, 0},
+ {120, 112, 98, 76, 45, 16, 2} };
+
+/*
+ * Update cpu_load for any missed ticks, due to tickless idle. The backlog
+ * would be when CPU is idle and so we just decay the old load without
+ * adding any new load.
+ */
+static unsigned long
+decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
+{
+ int j = 0;
+
+ if (!missed_updates)
+ return load;
+
+ if (missed_updates >= degrade_zero_ticks[idx])
+ return 0;
+
+ if (idx == 1)
+ return load >> missed_updates;
+
+ while (missed_updates) {
+ if (missed_updates % 2)
+ load = (load * degrade_factor[idx][j]) >> DEGRADE_SHIFT;
+
+ missed_updates >>= 1;
+ j++;
+ }
+ return load;
+}
+
/*
* Update rq->cpu_load[] statistics. This function is usually called every
- * scheduler tick (TICK_NSEC).
+ * scheduler tick (TICK_NSEC). With tickless idle this will not be called
+ * every tick. We fix it up based on jiffies.
*/
static void update_cpu_load(struct rq *this_rq)
{
unsigned long this_load = this_rq->load.weight;
+ unsigned long curr_jiffies = jiffies;
+ unsigned long pending_updates;
int i, scale;
this_rq->nr_load_updates++;
+ /* Avoid repeated calls on same jiffy, when moving in and out of idle */
+ if (curr_jiffies == this_rq->last_load_update_tick)
+ return;
+
+ pending_updates = curr_jiffies - this_rq->last_load_update_tick;
+ this_rq->last_load_update_tick = curr_jiffies;
+
/* Update our load: */
- for (i = 0, scale = 1; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
+ this_rq->cpu_load[0] = this_load; /* Fasttrack for idx 0 */
+ for (i = 1, scale = 2; i < CPU_LOAD_IDX_MAX; i++, scale += scale) {
unsigned long old_load, new_load;
/* scale is effectively 1 << i now, and >> i divides by scale */
old_load = this_rq->cpu_load[i];
+ old_load = decay_load_missed(old_load, pending_updates - 1, i);
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
* example.
*/
if (new_load > old_load)
- new_load += scale-1;
- this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) >> i;
+ new_load += scale - 1;
+
+ this_rq->cpu_load[i] = (old_load * (scale - 1) + new_load) >> i;
}
+}
+
+static void update_cpu_load_active(struct rq *this_rq)
+{
+ update_cpu_load(this_rq);
calc_load_account_active(this_rq);
}
raw_spin_lock(&rq->lock);
update_rq_clock(rq);
- update_cpu_load(rq);
+ update_cpu_load_active(rq);
curr->sched_class->task_tick(rq, curr, 0);
raw_spin_unlock(&rq->lock);
rq = cpu_rq(cpu);
rcu_note_context_switch(cpu);
prev = rq->curr;
- switch_count = &prev->nivcsw;
release_kernel_lock(prev);
need_resched_nonpreemptible:
raw_spin_lock_irq(&rq->lock);
clear_tsk_need_resched(prev);
+ switch_count = &prev->nivcsw;
if (prev->state && !(preempt_count() & PREEMPT_ACTIVE)) {
- if (unlikely(signal_pending_state(prev->state, prev)))
+ if (unlikely(signal_pending_state(prev->state, prev))) {
prev->state = TASK_RUNNING;
- else
+ } else {
+ /*
+ * If a worker is going to sleep, notify and
+ * ask workqueue whether it wants to wake up a
+ * task to maintain concurrency. If so, wake
+ * up the task.
+ */
+ if (prev->flags & PF_WQ_WORKER) {
+ struct task_struct *to_wakeup;
+
+ to_wakeup = wq_worker_sleeping(prev, cpu);
+ if (to_wakeup)
+ try_to_wake_up_local(to_wakeup);
+ }
deactivate_task(rq, prev, DEQUEUE_SLEEP);
+ }
switch_count = &prev->nvcsw;
}
context_switch(rq, prev, next); /* unlocks the rq */
/*
- * the context switch might have flipped the stack from under
- * us, hence refresh the local variables.
+ * The context switch have flipped the stack from under us
+ * and restored the local variables which were saved when
+ * this task called schedule() in the past. prev == current
+ * is still correct, but it can be moved to another cpu/rq.
*/
cpu = smp_processor_id();
rq = cpu_rq(cpu);
post_schedule(rq);
- if (unlikely(reacquire_kernel_lock(current) < 0)) {
- prev = rq->curr;
- switch_count = &prev->nivcsw;
+ if (unlikely(reacquire_kernel_lock(prev)))
goto need_resched_nonpreemptible;
- }
preempt_enable_no_resched();
if (need_resched())
*/
if (user && !capable(CAP_SYS_NICE)) {
if (rt_policy(policy)) {
- unsigned long rlim_rtprio;
-
- if (!lock_task_sighand(p, &flags))
- return -ESRCH;
- rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO);
- unlock_task_sighand(p, &flags);
+ unsigned long rlim_rtprio =
+ task_rlimit(p, RLIMIT_RTPRIO);
/* can't set/change the rt policy */
if (policy != p->policy && !rlim_rtprio)
*/
static struct notifier_block __cpuinitdata migration_notifier = {
.notifier_call = migration_call,
- .priority = 10
+ .priority = CPU_PRI_MIGRATION,
};
+static int __cpuinit sched_cpu_active(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_ONLINE:
+ case CPU_DOWN_FAILED:
+ set_cpu_active((long)hcpu, true);
+ return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
+}
+
+static int __cpuinit sched_cpu_inactive(struct notifier_block *nfb,
+ unsigned long action, void *hcpu)
+{
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_DOWN_PREPARE:
+ set_cpu_active((long)hcpu, false);
+ return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
+}
+
static int __init migration_init(void)
{
void *cpu = (void *)(long)smp_processor_id();
int err;
- /* Start one for the boot CPU: */
+ /* Initialize migration for the boot CPU */
err = migration_call(&migration_notifier, CPU_UP_PREPARE, cpu);
BUG_ON(err == NOTIFY_BAD);
migration_call(&migration_notifier, CPU_ONLINE, cpu);
register_cpu_notifier(&migration_notifier);
+ /* Register cpu active notifiers */
+ cpu_notifier(sched_cpu_active, CPU_PRI_SCHED_ACTIVE);
+ cpu_notifier(sched_cpu_inactive, CPU_PRI_SCHED_INACTIVE);
+
return 0;
}
early_initcall(migration_init);
free_rootdomain(old_rd);
}
-static int init_rootdomain(struct root_domain *rd, bool bootmem)
+static int init_rootdomain(struct root_domain *rd)
{
- gfp_t gfp = GFP_KERNEL;
-
memset(rd, 0, sizeof(*rd));
- if (bootmem)
- gfp = GFP_NOWAIT;
-
- if (!alloc_cpumask_var(&rd->span, gfp))
+ if (!alloc_cpumask_var(&rd->span, GFP_KERNEL))
goto out;
- if (!alloc_cpumask_var(&rd->online, gfp))
+ if (!alloc_cpumask_var(&rd->online, GFP_KERNEL))
goto free_span;
- if (!alloc_cpumask_var(&rd->rto_mask, gfp))
+ if (!alloc_cpumask_var(&rd->rto_mask, GFP_KERNEL))
goto free_online;
- if (cpupri_init(&rd->cpupri, bootmem) != 0)
+ if (cpupri_init(&rd->cpupri) != 0)
goto free_rto_mask;
return 0;
static void init_defrootdomain(void)
{
- init_rootdomain(&def_root_domain, true);
+ init_rootdomain(&def_root_domain);
atomic_set(&def_root_domain.refcount, 1);
}
if (!rd)
return NULL;
- if (init_rootdomain(rd, false) != 0) {
+ if (init_rootdomain(rd) != 0) {
kfree(rd);
return NULL;
}
}
#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
-#ifndef CONFIG_CPUSETS
/*
- * Add online and remove offline CPUs from the scheduler domains.
- * When cpusets are enabled they take over this function.
+ * Update cpusets according to cpu_active mask. If cpusets are
+ * disabled, cpuset_update_active_cpus() becomes a simple wrapper
+ * around partition_sched_domains().
*/
-static int update_sched_domains(struct notifier_block *nfb,
- unsigned long action, void *hcpu)
+static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
+ void *hcpu)
{
- switch (action) {
+ switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
- case CPU_ONLINE_FROZEN:
- case CPU_DOWN_PREPARE:
- case CPU_DOWN_PREPARE_FROZEN:
case CPU_DOWN_FAILED:
- case CPU_DOWN_FAILED_FROZEN:
- partition_sched_domains(1, NULL, NULL);
+ cpuset_update_active_cpus();
return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
+ }
+}
+static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
+ void *hcpu)
+{
+ switch (action & ~CPU_TASKS_FROZEN) {
+ case CPU_DOWN_PREPARE:
+ cpuset_update_active_cpus();
+ return NOTIFY_OK;
default:
return NOTIFY_DONE;
}
}
-#endif
static int update_runtime(struct notifier_block *nfb,
unsigned long action, void *hcpu)
mutex_unlock(&sched_domains_mutex);
put_online_cpus();
-#ifndef CONFIG_CPUSETS
- /* XXX: Theoretical race here - CPU may be hotplugged now */
- hotcpu_notifier(update_sched_domains, 0);
-#endif
+ hotcpu_notifier(cpuset_cpu_active, CPU_PRI_CPUSET_ACTIVE);
+ hotcpu_notifier(cpuset_cpu_inactive, CPU_PRI_CPUSET_INACTIVE);
/* RT runtime code needs to handle some hotplug events */
hotcpu_notifier(update_runtime, 0);
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
rq->cpu_load[j] = 0;
+
+ rq->last_load_update_tick = jiffies;
+
#ifdef CONFIG_SMP
rq->sd = NULL;
rq->rd = NULL;
rq->idle_stamp = 0;
rq->avg_idle = 2*sysctl_sched_migration_cost;
rq_attach_root(rq, &def_root_domain);
+#ifdef CONFIG_NO_HZ
+ rq->nohz_balance_kick = 0;
+ init_sched_softirq_csd(&per_cpu(remote_sched_softirq_cb, i));
+#endif
#endif
init_rq_hrtick(rq);
atomic_set(&rq->nr_iowait, 0);
zalloc_cpumask_var(&nohz_cpu_mask, GFP_NOWAIT);
#ifdef CONFIG_SMP
#ifdef CONFIG_NO_HZ
- zalloc_cpumask_var(&nohz.cpu_mask, GFP_NOWAIT);
- alloc_cpumask_var(&nohz.ilb_grp_nohz_mask, GFP_NOWAIT);
+ zalloc_cpumask_var(&nohz.idle_cpus_mask, GFP_NOWAIT);
+ alloc_cpumask_var(&nohz.grp_idle_mask, GFP_NOWAIT);
+ atomic_set(&nohz.load_balancer, nr_cpu_ids);
+ atomic_set(&nohz.first_pick_cpu, nr_cpu_ids);
+ atomic_set(&nohz.second_pick_cpu, nr_cpu_ids);
#endif
/* May be allocated at isolcpus cmdline parse time */
if (cpu_isolated_map == NULL)
git://bbs.cooldavid.org / net-next-2.6.git / blobdiff