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authorIngo Molnar <mingo@elte.hu>2009-09-19 11:27:32 +0200
committerIngo Molnar <mingo@elte.hu>2009-09-19 11:28:41 +0200
commit929bf0d0156562ce631728b6fa53d68004d456d2 (patch)
tree739063990a8077b29ef97e69d73bce94573daae4 /kernel/sched_fair.c
parentdef0a9b2573e00ab0b486cb5382625203ab4c4a6 (diff)
parent202c4675c55ddf6b443c7e057d2dff6b42ef71aa (diff)
Merge branch 'linus' into perfcounters/core
Merge reason: Bring in tracing changes we depend on. Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
-rw-r--r--kernel/sched_fair.c414
1 files changed, 261 insertions, 153 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index a097e909e80f..990b188803ce 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -712,7 +712,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
if (!initial) {
/* sleeps upto a single latency don't count. */
- if (sched_feat(NEW_FAIR_SLEEPERS)) {
+ if (sched_feat(FAIR_SLEEPERS)) {
unsigned long thresh = sysctl_sched_latency;
/*
@@ -726,6 +726,13 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
task_of(se)->policy != SCHED_IDLE))
thresh = calc_delta_fair(thresh, se);
+ /*
+ * Halve their sleep time's effect, to allow
+ * for a gentler effect of sleepers:
+ */
+ if (sched_feat(GENTLE_FAIR_SLEEPERS))
+ thresh >>= 1;
+
vruntime -= thresh;
}
}
@@ -758,10 +765,10 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int wakeup)
static void __clear_buddies(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- if (cfs_rq->last == se)
+ if (!se || cfs_rq->last == se)
cfs_rq->last = NULL;
- if (cfs_rq->next == se)
+ if (!se || cfs_rq->next == se)
cfs_rq->next = NULL;
}
@@ -1063,83 +1070,6 @@ static void yield_task_fair(struct rq *rq)
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.
- * Domains may include CPUs that are not usable for migration,
- * hence we need to mask them out (rq->rd->online)
- *
- * Returns the CPU we should wake onto.
- */
-#if defined(ARCH_HAS_SCHED_WAKE_IDLE)
-
-#define cpu_rd_active(cpu, rq) cpumask_test_cpu(cpu, rq->rd->online)
-
-static int wake_idle(int cpu, struct task_struct *p)
-{
- struct sched_domain *sd;
- int i;
- unsigned int chosen_wakeup_cpu;
- int this_cpu;
- struct rq *task_rq = task_rq(p);
-
- /*
- * At POWERSAVINGS_BALANCE_WAKEUP level, if both this_cpu and prev_cpu
- * are idle and this is not a kernel thread and this task's affinity
- * allows it to be moved to preferred cpu, then just move!
- */
-
- this_cpu = smp_processor_id();
- chosen_wakeup_cpu =
- cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu;
-
- if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP &&
- idle_cpu(cpu) && idle_cpu(this_cpu) &&
- p->mm && !(p->flags & PF_KTHREAD) &&
- cpu_isset(chosen_wakeup_cpu, p->cpus_allowed))
- return chosen_wakeup_cpu;
-
- /*
- * 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)->cfs.nr_running > 1)
- return cpu;
-
- for_each_domain(cpu, sd) {
- if ((sd->flags & SD_WAKE_IDLE)
- || ((sd->flags & SD_WAKE_IDLE_FAR)
- && !task_hot(p, task_rq->clock, sd))) {
- for_each_cpu_and(i, sched_domain_span(sd),
- &p->cpus_allowed) {
- if (cpu_rd_active(i, task_rq) && idle_cpu(i)) {
- if (i != task_cpu(p)) {
- schedstat_inc(p,
- se.nr_wakeups_idle);
- }
- return i;
- }
- }
- } else {
- break;
- }
- }
- return cpu;
-}
-#else /* !ARCH_HAS_SCHED_WAKE_IDLE*/
-static inline int wake_idle(int cpu, struct task_struct *p)
-{
- return cpu;
-}
-#endif
-
#ifdef CONFIG_SMP
#ifdef CONFIG_FAIR_GROUP_SCHED
@@ -1226,25 +1156,34 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu,
#endif
-static int
-wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
- struct task_struct *p, int prev_cpu, int this_cpu, int sync,
- int idx, unsigned long load, unsigned long this_load,
- unsigned int imbalance)
+static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
{
- struct task_struct *curr = this_rq->curr;
- struct task_group *tg;
- unsigned long tl = this_load;
+ struct task_struct *curr = current;
+ unsigned long this_load, load;
+ int idx, this_cpu, prev_cpu;
unsigned long tl_per_task;
+ unsigned int imbalance;
+ struct task_group *tg;
unsigned long weight;
int balanced;
- if (!(this_sd->flags & SD_WAKE_AFFINE) || !sched_feat(AFFINE_WAKEUPS))
- return 0;
+ idx = sd->wake_idx;
+ this_cpu = smp_processor_id();
+ prev_cpu = task_cpu(p);
+ load = source_load(prev_cpu, idx);
+ this_load = target_load(this_cpu, idx);
- if (sync && (curr->se.avg_overlap > sysctl_sched_migration_cost ||
- p->se.avg_overlap > sysctl_sched_migration_cost))
- sync = 0;
+ if (sync) {
+ if (sched_feat(SYNC_LESS) &&
+ (curr->se.avg_overlap > sysctl_sched_migration_cost ||
+ p->se.avg_overlap > sysctl_sched_migration_cost))
+ sync = 0;
+ } else {
+ if (sched_feat(SYNC_MORE) &&
+ (curr->se.avg_overlap < sysctl_sched_migration_cost &&
+ p->se.avg_overlap < sysctl_sched_migration_cost))
+ sync = 1;
+ }
/*
* If sync wakeup then subtract the (maximum possible)
@@ -1255,24 +1194,26 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
tg = task_group(current);
weight = current->se.load.weight;
- tl += effective_load(tg, this_cpu, -weight, -weight);
+ this_load += effective_load(tg, this_cpu, -weight, -weight);
load += effective_load(tg, prev_cpu, 0, -weight);
}
tg = task_group(p);
weight = p->se.load.weight;
+ imbalance = 100 + (sd->imbalance_pct - 100) / 2;
+
/*
* In low-load situations, where prev_cpu is idle and this_cpu is idle
- * due to the sync cause above having dropped tl to 0, we'll always have
- * an imbalance, but there's really nothing you can do about that, so
- * that's good too.
+ * due to the sync cause above having dropped this_load to 0, we'll
+ * always have an imbalance, but there's really nothing you can do
+ * about that, so that's good too.
*
* Otherwise check if either cpus are near enough in load to allow this
* task to be woken on this_cpu.
*/
- balanced = !tl ||
- 100*(tl + effective_load(tg, this_cpu, weight, weight)) <=
+ balanced = !this_load ||
+ 100*(this_load + effective_load(tg, this_cpu, weight, weight)) <=
imbalance*(load + effective_load(tg, prev_cpu, 0, weight));
/*
@@ -1286,14 +1227,15 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
schedstat_inc(p, se.nr_wakeups_affine_attempts);
tl_per_task = cpu_avg_load_per_task(this_cpu);
- if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=
- tl_per_task)) {
+ if (balanced ||
+ (this_load <= load &&
+ this_load + target_load(prev_cpu, idx) <= tl_per_task)) {
/*
* 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(sd, ttwu_move_affine);
schedstat_inc(p, se.nr_wakeups_affine);
return 1;
@@ -1301,65 +1243,215 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
return 0;
}
-static int select_task_rq_fair(struct task_struct *p, int sync)
+/*
+ * find_idlest_group finds and returns the least busy CPU group within the
+ * domain.
+ */
+static struct sched_group *
+find_idlest_group(struct sched_domain *sd, struct task_struct *p,
+ int this_cpu, int load_idx)
{
- struct sched_domain *sd, *this_sd = NULL;
- int prev_cpu, this_cpu, new_cpu;
- unsigned long load, this_load;
- struct rq *this_rq;
- unsigned int imbalance;
- int idx;
+ struct sched_group *idlest = NULL, *this = NULL, *group = sd->groups;
+ unsigned long min_load = ULONG_MAX, this_load = 0;
+ int imbalance = 100 + (sd->imbalance_pct-100)/2;
- prev_cpu = task_cpu(p);
- this_cpu = smp_processor_id();
- this_rq = cpu_rq(this_cpu);
- new_cpu = prev_cpu;
+ do {
+ unsigned long load, avg_load;
+ int local_group;
+ int i;
- /*
- * 'this_sd' is the first domain that both
- * this_cpu and prev_cpu are present in:
- */
- for_each_domain(this_cpu, sd) {
- if (cpumask_test_cpu(prev_cpu, sched_domain_span(sd))) {
- this_sd = sd;
- break;
+ /* Skip over this group if it has no CPUs allowed */
+ if (!cpumask_intersects(sched_group_cpus(group),
+ &p->cpus_allowed))
+ continue;
+
+ local_group = cpumask_test_cpu(this_cpu,
+ sched_group_cpus(group));
+
+ /* Tally up the load of all CPUs in the group */
+ avg_load = 0;
+
+ for_each_cpu(i, sched_group_cpus(group)) {
+ /* Bias balancing toward cpus of our domain */
+ if (local_group)
+ load = source_load(i, load_idx);
+ else
+ load = target_load(i, load_idx);
+
+ avg_load += load;
+ }
+
+ /* Adjust by relative CPU power of the group */
+ avg_load = (avg_load * SCHED_LOAD_SCALE) / group->cpu_power;
+
+ if (local_group) {
+ this_load = avg_load;
+ this = group;
+ } else if (avg_load < min_load) {
+ min_load = avg_load;
+ idlest = group;
+ }
+ } while (group = group->next, group != sd->groups);
+
+ if (!idlest || 100*this_load < imbalance*min_load)
+ return NULL;
+ return idlest;
+}
+
+/*
+ * find_idlest_cpu - find the idlest cpu among the cpus in group.
+ */
+static int
+find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
+{
+ unsigned long load, min_load = ULONG_MAX;
+ int idlest = -1;
+ int i;
+
+ /* Traverse only the allowed CPUs */
+ for_each_cpu_and(i, sched_group_cpus(group), &p->cpus_allowed) {
+ load = weighted_cpuload(i);
+
+ if (load < min_load || (load == min_load && i == this_cpu)) {
+ min_load = load;
+ idlest = i;
}
}
- if (unlikely(!cpumask_test_cpu(this_cpu, &p->cpus_allowed)))
- goto out;
+ return idlest;
+}
- /*
- * Check for affine wakeup and passive balancing possibilities.
- */
- if (!this_sd)
+/*
+ * sched_balance_self: balance the current task (running on cpu) in domains
+ * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
+ * SD_BALANCE_EXEC.
+ *
+ * Balance, ie. select the least loaded group.
+ *
+ * Returns the target CPU number, or the same CPU if no balancing is needed.
+ *
+ * preempt must be disabled.
+ */
+static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags)
+{
+ struct sched_domain *tmp, *affine_sd = NULL, *sd = NULL;
+ int cpu = smp_processor_id();
+ int prev_cpu = task_cpu(p);
+ int new_cpu = cpu;
+ int want_affine = 0;
+ int want_sd = 1;
+ int sync = wake_flags & WF_SYNC;
+
+ if (sd_flag & SD_BALANCE_WAKE) {
+ if (sched_feat(AFFINE_WAKEUPS))
+ want_affine = 1;
+ new_cpu = prev_cpu;
+ }
+
+ rcu_read_lock();
+ for_each_domain(cpu, tmp) {
+ /*
+ * If power savings logic is enabled for a domain, see if we
+ * are not overloaded, if so, don't balance wider.
+ */
+ if (tmp->flags & (SD_POWERSAVINGS_BALANCE|SD_PREFER_LOCAL)) {
+ unsigned long power = 0;
+ unsigned long nr_running = 0;
+ unsigned long capacity;
+ int i;
+
+ for_each_cpu(i, sched_domain_span(tmp)) {
+ power += power_of(i);
+ nr_running += cpu_rq(i)->cfs.nr_running;
+ }
+
+ capacity = DIV_ROUND_CLOSEST(power, SCHED_LOAD_SCALE);
+
+ if (tmp->flags & SD_POWERSAVINGS_BALANCE)
+ nr_running /= 2;
+
+ if (nr_running < capacity)
+ want_sd = 0;
+ }
+
+ if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
+ cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
+
+ affine_sd = tmp;
+ want_affine = 0;
+ }
+
+ if (!want_sd && !want_affine)
+ break;
+
+ if (!(tmp->flags & sd_flag))
+ continue;
+
+ if (want_sd)
+ sd = tmp;
+ }
+
+ if (sched_feat(LB_SHARES_UPDATE)) {
+ /*
+ * Pick the largest domain to update shares over
+ */
+ tmp = sd;
+ if (affine_sd && (!tmp ||
+ cpumask_weight(sched_domain_span(affine_sd)) >
+ cpumask_weight(sched_domain_span(sd))))
+ tmp = affine_sd;
+
+ if (tmp)
+ update_shares(tmp);
+ }
+
+ if (affine_sd && wake_affine(affine_sd, p, sync)) {
+ new_cpu = cpu;
goto out;
+ }
- idx = this_sd->wake_idx;
+ while (sd) {
+ int load_idx = sd->forkexec_idx;
+ struct sched_group *group;
+ int weight;
- imbalance = 100 + (this_sd->imbalance_pct - 100) / 2;
+ if (!(sd->flags & sd_flag)) {
+ sd = sd->child;
+ continue;
+ }
- load = source_load(prev_cpu, idx);
- this_load = target_load(this_cpu, idx);
+ if (sd_flag & SD_BALANCE_WAKE)
+ load_idx = sd->wake_idx;
- if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
- load, this_load, imbalance))
- return this_cpu;
+ group = find_idlest_group(sd, p, cpu, load_idx);
+ if (!group) {
+ sd = sd->child;
+ continue;
+ }
- /*
- * 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);
- return this_cpu;
+ new_cpu = find_idlest_cpu(group, p, cpu);
+ if (new_cpu == -1 || new_cpu == cpu) {
+ /* Now try balancing at a lower domain level of cpu */
+ sd = sd->child;
+ continue;
}
+
+ /* Now try balancing at a lower domain level of new_cpu */
+ cpu = new_cpu;
+ weight = cpumask_weight(sched_domain_span(sd));
+ sd = NULL;
+ for_each_domain(cpu, tmp) {
+ if (weight <= cpumask_weight(sched_domain_span(tmp)))
+ break;
+ if (tmp->flags & sd_flag)
+ sd = tmp;
+ }
+ /* while loop will break here if sd == NULL */
}
out:
- return wake_idle(new_cpu, p);
+ rcu_read_unlock();
+ return new_cpu;
}
#endif /* CONFIG_SMP */
@@ -1472,11 +1564,12 @@ static void set_next_buddy(struct sched_entity *se)
/*
* Preempt the current task with a newly woken task if needed:
*/
-static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
+static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
{
struct task_struct *curr = rq->curr;
struct sched_entity *se = &curr->se, *pse = &p->se;
struct cfs_rq *cfs_rq = task_cfs_rq(curr);
+ int sync = wake_flags & WF_SYNC;
update_curr(cfs_rq);
@@ -1502,7 +1595,8 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
*/
if (sched_feat(LAST_BUDDY) && likely(se->on_rq && curr != rq->idle))
set_last_buddy(se);
- set_next_buddy(pse);
+ if (sched_feat(NEXT_BUDDY) && !(wake_flags & WF_FORK))
+ set_next_buddy(pse);
/*
* We can come here with TIF_NEED_RESCHED already set from new task
@@ -1524,16 +1618,25 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int sync)
return;
}
- if (!sched_feat(WAKEUP_PREEMPT))
- return;
-
- if (sched_feat(WAKEUP_OVERLAP) && (sync ||
- (se->avg_overlap < sysctl_sched_migration_cost &&
- pse->avg_overlap < sysctl_sched_migration_cost))) {
+ if ((sched_feat(WAKEUP_SYNC) && sync) ||
+ (sched_feat(WAKEUP_OVERLAP) &&
+ (se->avg_overlap < sysctl_sched_migration_cost &&
+ pse->avg_overlap < sysctl_sched_migration_cost))) {
resched_task(curr);
return;
}
+ if (sched_feat(WAKEUP_RUNNING)) {
+ if (pse->avg_running < se->avg_running) {
+ set_next_buddy(pse);
+ resched_task(curr);
+ return;
+ }
+ }
+
+ if (!sched_feat(WAKEUP_PREEMPT))
+ return;
+
find_matching_se(&se, &pse);
BUG_ON(!pse);
@@ -1556,8 +1659,13 @@ static struct task_struct *pick_next_task_fair(struct rq *rq)
/*
* If se was a buddy, clear it so that it will have to earn
* the favour again.
+ *
+ * If se was not a buddy, clear the buddies because neither
+ * was elegible to run, let them earn it again.
+ *
+ * IOW. unconditionally clear buddies.
*/
- __clear_buddies(cfs_rq, se);
+ __clear_buddies(cfs_rq, NULL);
set_next_entity(cfs_rq, se);
cfs_rq = group_cfs_rq(se);
} while (cfs_rq);