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Subject[GIT PULL] scheduler changes for v4.1
Linus,

Please pull the latest sched-core-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched-core-for-linus

# HEAD: 62a935b256f68a71697716595347209fb5275426 sched/core: Drop debugging leftover trace_printk call

Major changes:

- Reworked CPU capacity code, for better SMP load balancing on
systems with assymetric CPUs. (Vincent Guittot, Morten Rasmussen)

- Reworked RT task SMP balancing to be push based instead of pull
based, to reduce latencies on large CPU count systems. (Steven Rostedt)

- SCHED_DEADLINE support updates and fixes. (Juri Lelli)

- SCHED_DEADLINE task migration support during CPU hotplug. (Wanpeng Li)

- x86 mwait-idle optimizations and fixes. (Mike Galbraith, Len Brown)

- sched/numa improvements. (Rik van Riel)

- various cleanups

Thanks,

Ingo

------------------>
Abel Vesa (1):
sched/core: Remove unused argument from init_[rt|dl]_rq()

Borislav Petkov (1):
sched/core: Drop debugging leftover trace_printk call

Jan Beulich (1):
sched/numa: Avoid some pointless iterations

Juri Lelli (2):
sched/deadline: Always enqueue on previous rq when dl_task_timer() fires
sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()

Len Brown (1):
sched/idle/x86: Restore mwait_idle() to fix boot hangs, to improve power savings and to improve performance

Mike Galbraith (1):
sched/idle/x86: Optimize unnecessary mwait_idle() resched IPIs

Morten Rasmussen (2):
sched: Track group sched_entity usage contributions
sched: Make sched entity usage tracking scale-invariant

Peter Zijlstra (1):
sched: Optimize freq invariant accounting

Preeti U Murthy (1):
sched: Improve load balancing in the presence of idle CPUs

Rik van Riel (2):
sched/numa: Do not move past the balance point if unbalanced
sched/rt/nohz: Stop scheduler tick if running realtime task

Steven Rostedt (2):
irq_work: Fix build failure when CONFIG_IRQ_WORK is not defined
sched/rt: Use IPI to trigger RT task push migration instead of pulling

Vincent Guittot (9):
sched: Add sched_avg::utilization_avg_contrib
sched: Remove frequency scaling from cpu_capacity
sched: Make scale_rt invariant with frequency
sched: Add struct rq::cpu_capacity_orig
sched: Calculate CPU's usage statistic and put it into struct sg_lb_stats::group_usage
sched: Replace capacity_factor by usage
sched: Remove unused struct sched_group_capacity::capacity_orig
sched: Add SD_PREFER_SIBLING for SMT level
sched: Move CFS tasks to CPUs with higher capacity

Wanpeng Li (4):
sched/deadline: Add rq->clock update skip for dl task yield
sched/deadline: Avoid a superfluous check
sched/deadline: Fix rt runtime corruption when dl fails its global constraints
sched/deadline: Support DL task migration during CPU hotplug


arch/x86/include/asm/mwait.h | 8 +
arch/x86/kernel/process.c | 51 ++++++
include/linux/irq_work.h | 3 +-
include/linux/sched.h | 21 ++-
kernel/sched/core.c | 96 +++++-----
kernel/sched/deadline.c | 77 ++++++--
kernel/sched/debug.c | 12 +-
kernel/sched/fair.c | 425 ++++++++++++++++++++++++++-----------------
kernel/sched/features.h | 13 ++
kernel/sched/rt.c | 181 +++++++++++++++++-
kernel/sched/sched.h | 38 +++-
11 files changed, 690 insertions(+), 235 deletions(-)

diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index a1410db38a1a..653dfa7662e1 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -30,6 +30,14 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
:: "a" (eax), "c" (ecx));
}

+static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
+{
+ trace_hardirqs_on();
+ /* "mwait %eax, %ecx;" */
+ asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
+ :: "a" (eax), "c" (ecx));
+}
+
/*
* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
* which can obviate IPI to trigger checking of need_resched.
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 046e2d620bbe..a388bb883128 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -24,6 +24,7 @@
#include <asm/syscalls.h>
#include <asm/idle.h>
#include <asm/uaccess.h>
+#include <asm/mwait.h>
#include <asm/i387.h>
#include <asm/fpu-internal.h>
#include <asm/debugreg.h>
@@ -399,6 +400,53 @@ static void amd_e400_idle(void)
default_idle();
}

+/*
+ * Intel Core2 and older machines prefer MWAIT over HALT for C1.
+ * We can't rely on cpuidle installing MWAIT, because it will not load
+ * on systems that support only C1 -- so the boot default must be MWAIT.
+ *
+ * Some AMD machines are the opposite, they depend on using HALT.
+ *
+ * So for default C1, which is used during boot until cpuidle loads,
+ * use MWAIT-C1 on Intel HW that has it, else use HALT.
+ */
+static int prefer_mwait_c1_over_halt(const struct cpuinfo_x86 *c)
+{
+ if (c->x86_vendor != X86_VENDOR_INTEL)
+ return 0;
+
+ if (!cpu_has(c, X86_FEATURE_MWAIT))
+ return 0;
+
+ return 1;
+}
+
+/*
+ * MONITOR/MWAIT with no hints, used for default default C1 state.
+ * This invokes MWAIT with interrutps enabled and no flags,
+ * which is backwards compatible with the original MWAIT implementation.
+ */
+
+static void mwait_idle(void)
+{
+ if (!current_set_polling_and_test()) {
+ if (this_cpu_has(X86_BUG_CLFLUSH_MONITOR)) {
+ smp_mb(); /* quirk */
+ clflush((void *)&current_thread_info()->flags);
+ smp_mb(); /* quirk */
+ }
+
+ __monitor((void *)&current_thread_info()->flags, 0, 0);
+ if (!need_resched())
+ __sti_mwait(0, 0);
+ else
+ local_irq_enable();
+ } else {
+ local_irq_enable();
+ }
+ __current_clr_polling();
+}
+
void select_idle_routine(const struct cpuinfo_x86 *c)
{
#ifdef CONFIG_SMP
@@ -412,6 +460,9 @@ void select_idle_routine(const struct cpuinfo_x86 *c)
/* E400: APIC timer interrupt does not wake up CPU from C1e */
pr_info("using AMD E400 aware idle routine\n");
x86_idle = amd_e400_idle;
+ } else if (prefer_mwait_c1_over_halt(c)) {
+ pr_info("using mwait in idle threads\n");
+ x86_idle = mwait_idle;
} else
x86_idle = default_idle;
}
diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
index bf3fe719c7ce..47b9ebd4a74f 100644
--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -38,16 +38,17 @@ bool irq_work_queue(struct irq_work *work);
bool irq_work_queue_on(struct irq_work *work, int cpu);
#endif

-void irq_work_run(void);
void irq_work_tick(void);
void irq_work_sync(struct irq_work *work);

#ifdef CONFIG_IRQ_WORK
#include <asm/irq_work.h>

+void irq_work_run(void);
bool irq_work_needs_cpu(void);
#else
static inline bool irq_work_needs_cpu(void) { return false; }
+static inline void irq_work_run(void) { }
#endif

#endif /* _LINUX_IRQ_WORK_H */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 6d77432e14ff..fdca05c5f812 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1115,15 +1115,28 @@ struct load_weight {
};

struct sched_avg {
+ u64 last_runnable_update;
+ s64 decay_count;
+ /*
+ * utilization_avg_contrib describes the amount of time that a
+ * sched_entity is running on a CPU. It is based on running_avg_sum
+ * and is scaled in the range [0..SCHED_LOAD_SCALE].
+ * load_avg_contrib described the amount of time that a sched_entity
+ * is runnable on a rq. It is based on both runnable_avg_sum and the
+ * weight of the task.
+ */
+ unsigned long load_avg_contrib, utilization_avg_contrib;
/*
* These sums represent an infinite geometric series and so are bound
* above by 1024/(1-y). Thus we only need a u32 to store them for all
* choices of y < 1-2^(-32)*1024.
+ * running_avg_sum reflects the time that the sched_entity is
+ * effectively running on the CPU.
+ * runnable_avg_sum represents the amount of time a sched_entity is on
+ * a runqueue which includes the running time that is monitored by
+ * running_avg_sum.
*/
- u32 runnable_avg_sum, runnable_avg_period;
- u64 last_runnable_update;
- s64 decay_count;
- unsigned long load_avg_contrib;
+ u32 runnable_avg_sum, avg_period, running_avg_sum;
};

#ifdef CONFIG_SCHEDSTATS
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 62671f53202a..8027cfd699d0 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -690,6 +690,23 @@ static inline bool got_nohz_idle_kick(void)
bool sched_can_stop_tick(void)
{
/*
+ * FIFO realtime policy runs the highest priority task. Other runnable
+ * tasks are of a lower priority. The scheduler tick does nothing.
+ */
+ if (current->policy == SCHED_FIFO)
+ return true;
+
+ /*
+ * Round-robin realtime tasks time slice with other tasks at the same
+ * realtime priority. Is this task the only one at this priority?
+ */
+ if (current->policy == SCHED_RR) {
+ struct sched_rt_entity *rt_se = &current->rt;
+
+ return rt_se->run_list.prev == rt_se->run_list.next;
+ }
+
+ /*
* More than one running task need preemption.
* nr_running update is assumed to be visible
* after IPI is sent from wakers.
@@ -5320,36 +5337,13 @@ static int sched_cpu_active(struct notifier_block *nfb,
static int sched_cpu_inactive(struct notifier_block *nfb,
unsigned long action, void *hcpu)
{
- unsigned long flags;
- long cpu = (long)hcpu;
- struct dl_bw *dl_b;
-
switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
- set_cpu_active(cpu, false);
-
- /* explicitly allow suspend */
- if (!(action & CPU_TASKS_FROZEN)) {
- bool overflow;
- int cpus;
-
- rcu_read_lock_sched();
- dl_b = dl_bw_of(cpu);
-
- raw_spin_lock_irqsave(&dl_b->lock, flags);
- cpus = dl_bw_cpus(cpu);
- overflow = __dl_overflow(dl_b, cpus, 0, 0);
- raw_spin_unlock_irqrestore(&dl_b->lock, flags);
-
- rcu_read_unlock_sched();
-
- if (overflow)
- return notifier_from_errno(-EBUSY);
- }
+ set_cpu_active((long)hcpu, false);
return NOTIFY_OK;
+ default:
+ return NOTIFY_DONE;
}
-
- return NOTIFY_DONE;
}

static int __init migration_init(void)
@@ -5430,17 +5424,6 @@ static int sched_domain_debug_one(struct sched_domain *sd, int cpu, int level,
break;
}

- /*
- * Even though we initialize ->capacity to something semi-sane,
- * we leave capacity_orig unset. This allows us to detect if
- * domain iteration is still funny without causing /0 traps.
- */
- if (!group->sgc->capacity_orig) {
- printk(KERN_CONT "\n");
- printk(KERN_ERR "ERROR: domain->cpu_capacity not set\n");
- break;
- }
-
if (!cpumask_weight(sched_group_cpus(group))) {
printk(KERN_CONT "\n");
printk(KERN_ERR "ERROR: empty group\n");
@@ -5924,7 +5907,6 @@ build_overlap_sched_groups(struct sched_domain *sd, int cpu)
* die on a /0 trap.
*/
sg->sgc->capacity = SCHED_CAPACITY_SCALE * cpumask_weight(sg_span);
- sg->sgc->capacity_orig = sg->sgc->capacity;

/*
* Make sure the first group of this domain contains the
@@ -6235,6 +6217,7 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
*/

if (sd->flags & SD_SHARE_CPUCAPACITY) {
+ sd->flags |= SD_PREFER_SIBLING;
sd->imbalance_pct = 110;
sd->smt_gain = 1178; /* ~15% */

@@ -7000,7 +6983,6 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
*/

case CPU_ONLINE:
- case CPU_DOWN_FAILED:
cpuset_update_active_cpus(true);
break;
default:
@@ -7012,8 +6994,30 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
void *hcpu)
{
- switch (action) {
+ unsigned long flags;
+ long cpu = (long)hcpu;
+ struct dl_bw *dl_b;
+
+ switch (action & ~CPU_TASKS_FROZEN) {
case CPU_DOWN_PREPARE:
+ /* explicitly allow suspend */
+ if (!(action & CPU_TASKS_FROZEN)) {
+ bool overflow;
+ int cpus;
+
+ rcu_read_lock_sched();
+ dl_b = dl_bw_of(cpu);
+
+ raw_spin_lock_irqsave(&dl_b->lock, flags);
+ cpus = dl_bw_cpus(cpu);
+ overflow = __dl_overflow(dl_b, cpus, 0, 0);
+ raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+
+ rcu_read_unlock_sched();
+
+ if (overflow)
+ return notifier_from_errno(-EBUSY);
+ }
cpuset_update_active_cpus(false);
break;
case CPU_DOWN_PREPARE_FROZEN:
@@ -7158,8 +7162,8 @@ void __init sched_init(void)
rq->calc_load_active = 0;
rq->calc_load_update = jiffies + LOAD_FREQ;
init_cfs_rq(&rq->cfs);
- init_rt_rq(&rq->rt, rq);
- init_dl_rq(&rq->dl, rq);
+ init_rt_rq(&rq->rt);
+ init_dl_rq(&rq->dl);
#ifdef CONFIG_FAIR_GROUP_SCHED
root_task_group.shares = ROOT_TASK_GROUP_LOAD;
INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
@@ -7199,7 +7203,7 @@ void __init sched_init(void)
#ifdef CONFIG_SMP
rq->sd = NULL;
rq->rd = NULL;
- rq->cpu_capacity = SCHED_CAPACITY_SCALE;
+ rq->cpu_capacity = rq->cpu_capacity_orig = SCHED_CAPACITY_SCALE;
rq->post_schedule = 0;
rq->active_balance = 0;
rq->next_balance = jiffies;
@@ -7798,7 +7802,7 @@ static int sched_rt_global_constraints(void)
}
#endif /* CONFIG_RT_GROUP_SCHED */

-static int sched_dl_global_constraints(void)
+static int sched_dl_global_validate(void)
{
u64 runtime = global_rt_runtime();
u64 period = global_rt_period();
@@ -7899,11 +7903,11 @@ int sched_rt_handler(struct ctl_table *table, int write,
if (ret)
goto undo;

- ret = sched_rt_global_constraints();
+ ret = sched_dl_global_validate();
if (ret)
goto undo;

- ret = sched_dl_global_constraints();
+ ret = sched_rt_global_constraints();
if (ret)
goto undo;

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 3fa8fa6d9403..5e95145088fd 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -69,7 +69,7 @@ void init_dl_bw(struct dl_bw *dl_b)
dl_b->total_bw = 0;
}

-void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq)
+void init_dl_rq(struct dl_rq *dl_rq)
{
dl_rq->rb_root = RB_ROOT;

@@ -218,6 +218,52 @@ static inline void set_post_schedule(struct rq *rq)
rq->post_schedule = has_pushable_dl_tasks(rq);
}

+static struct rq *find_lock_later_rq(struct task_struct *task, struct rq *rq);
+
+static void dl_task_offline_migration(struct rq *rq, struct task_struct *p)
+{
+ struct rq *later_rq = NULL;
+ bool fallback = false;
+
+ later_rq = find_lock_later_rq(p, rq);
+
+ if (!later_rq) {
+ int cpu;
+
+ /*
+ * If we cannot preempt any rq, fall back to pick any
+ * online cpu.
+ */
+ fallback = true;
+ cpu = cpumask_any_and(cpu_active_mask, tsk_cpus_allowed(p));
+ if (cpu >= nr_cpu_ids) {
+ /*
+ * Fail to find any suitable cpu.
+ * The task will never come back!
+ */
+ BUG_ON(dl_bandwidth_enabled());
+
+ /*
+ * If admission control is disabled we
+ * try a little harder to let the task
+ * run.
+ */
+ cpu = cpumask_any(cpu_active_mask);
+ }
+ later_rq = cpu_rq(cpu);
+ double_lock_balance(rq, later_rq);
+ }
+
+ deactivate_task(rq, p, 0);
+ set_task_cpu(p, later_rq->cpu);
+ activate_task(later_rq, p, ENQUEUE_REPLENISH);
+
+ if (!fallback)
+ resched_curr(later_rq);
+
+ double_unlock_balance(rq, later_rq);
+}
+
#else

static inline
@@ -514,7 +560,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
unsigned long flags;
struct rq *rq;

- rq = task_rq_lock(current, &flags);
+ rq = task_rq_lock(p, &flags);

/*
* We need to take care of several possible races here:
@@ -536,6 +582,17 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
sched_clock_tick();
update_rq_clock(rq);

+#ifdef CONFIG_SMP
+ /*
+ * If we find that the rq the task was on is no longer
+ * available, we need to select a new rq.
+ */
+ if (unlikely(!rq->online)) {
+ dl_task_offline_migration(rq, p);
+ goto unlock;
+ }
+#endif
+
/*
* If the throttle happened during sched-out; like:
*
@@ -569,7 +626,7 @@ static enum hrtimer_restart dl_task_timer(struct hrtimer *timer)
push_dl_task(rq);
#endif
unlock:
- task_rq_unlock(rq, current, &flags);
+ task_rq_unlock(rq, p, &flags);

return HRTIMER_NORESTART;
}
@@ -914,6 +971,12 @@ static void yield_task_dl(struct rq *rq)
}
update_rq_clock(rq);
update_curr_dl(rq);
+ /*
+ * Tell update_rq_clock() that we've just updated,
+ * so we don't do microscopic update in schedule()
+ * and double the fastpath cost.
+ */
+ rq_clock_skip_update(rq, true);
}

#ifdef CONFIG_SMP
@@ -1659,14 +1722,6 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
{
int check_resched = 1;

- /*
- * If p is throttled, don't consider the possibility
- * of preempting rq->curr, the check will be done right
- * after its runtime will get replenished.
- */
- if (unlikely(p->dl.dl_throttled))
- return;
-
if (task_on_rq_queued(p) && rq->curr != p) {
#ifdef CONFIG_SMP
if (p->nr_cpus_allowed > 1 && rq->dl.overloaded &&
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 8baaf858d25c..a245c1fc6f0a 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -71,7 +71,7 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
if (!se) {
struct sched_avg *avg = &cpu_rq(cpu)->avg;
P(avg->runnable_avg_sum);
- P(avg->runnable_avg_period);
+ P(avg->avg_period);
return;
}

@@ -94,8 +94,10 @@ static void print_cfs_group_stats(struct seq_file *m, int cpu, struct task_group
P(se->load.weight);
#ifdef CONFIG_SMP
P(se->avg.runnable_avg_sum);
- P(se->avg.runnable_avg_period);
+ P(se->avg.running_avg_sum);
+ P(se->avg.avg_period);
P(se->avg.load_avg_contrib);
+ P(se->avg.utilization_avg_contrib);
P(se->avg.decay_count);
#endif
#undef PN
@@ -214,6 +216,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq)
cfs_rq->runnable_load_avg);
SEQ_printf(m, " .%-30s: %ld\n", "blocked_load_avg",
cfs_rq->blocked_load_avg);
+ SEQ_printf(m, " .%-30s: %ld\n", "utilization_load_avg",
+ cfs_rq->utilization_load_avg);
#ifdef CONFIG_FAIR_GROUP_SCHED
SEQ_printf(m, " .%-30s: %ld\n", "tg_load_contrib",
cfs_rq->tg_load_contrib);
@@ -636,8 +640,10 @@ void proc_sched_show_task(struct task_struct *p, struct seq_file *m)
P(se.load.weight);
#ifdef CONFIG_SMP
P(se.avg.runnable_avg_sum);
- P(se.avg.runnable_avg_period);
+ P(se.avg.running_avg_sum);
+ P(se.avg.avg_period);
P(se.avg.load_avg_contrib);
+ P(se.avg.utilization_avg_contrib);
P(se.avg.decay_count);
#endif
P(policy);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 7ce18f3c097a..46855d06666a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -670,6 +670,7 @@ static int select_idle_sibling(struct task_struct *p, int cpu);
static unsigned long task_h_load(struct task_struct *p);

static inline void __update_task_entity_contrib(struct sched_entity *se);
+static inline void __update_task_entity_utilization(struct sched_entity *se);

/* Give new task start runnable values to heavy its load in infant time */
void init_task_runnable_average(struct task_struct *p)
@@ -677,9 +678,10 @@ void init_task_runnable_average(struct task_struct *p)
u32 slice;

slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
- p->se.avg.runnable_avg_sum = slice;
- p->se.avg.runnable_avg_period = slice;
+ p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = slice;
+ p->se.avg.avg_period = slice;
__update_task_entity_contrib(&p->se);
+ __update_task_entity_utilization(&p->se);
}
#else
void init_task_runnable_average(struct task_struct *p)
@@ -1196,9 +1198,11 @@ static void task_numa_assign(struct task_numa_env *env,
static bool load_too_imbalanced(long src_load, long dst_load,
struct task_numa_env *env)
{
- long imb, old_imb;
- long orig_src_load, orig_dst_load;
long src_capacity, dst_capacity;
+ long orig_src_load;
+ long load_a, load_b;
+ long moved_load;
+ long imb;

/*
* The load is corrected for the CPU capacity available on each node.
@@ -1211,30 +1215,39 @@ static bool load_too_imbalanced(long src_load, long dst_load,
dst_capacity = env->dst_stats.compute_capacity;

/* We care about the slope of the imbalance, not the direction. */
- if (dst_load < src_load)
- swap(dst_load, src_load);
+ load_a = dst_load;
+ load_b = src_load;
+ if (load_a < load_b)
+ swap(load_a, load_b);

/* Is the difference below the threshold? */
- imb = dst_load * src_capacity * 100 -
- src_load * dst_capacity * env->imbalance_pct;
+ imb = load_a * src_capacity * 100 -
+ load_b * dst_capacity * env->imbalance_pct;
if (imb <= 0)
return false;

/*
* The imbalance is above the allowed threshold.
- * Compare it with the old imbalance.
+ * Allow a move that brings us closer to a balanced situation,
+ * without moving things past the point of balance.
*/
orig_src_load = env->src_stats.load;
- orig_dst_load = env->dst_stats.load;

- if (orig_dst_load < orig_src_load)
- swap(orig_dst_load, orig_src_load);
-
- old_imb = orig_dst_load * src_capacity * 100 -
- orig_src_load * dst_capacity * env->imbalance_pct;
+ /*
+ * In a task swap, there will be one load moving from src to dst,
+ * and another moving back. This is the net sum of both moves.
+ * A simple task move will always have a positive value.
+ * Allow the move if it brings the system closer to a balanced
+ * situation, without crossing over the balance point.
+ */
+ moved_load = orig_src_load - src_load;

- /* Would this change make things worse? */
- return (imb > old_imb);
+ if (moved_load > 0)
+ /* Moving src -> dst. Did we overshoot balance? */
+ return src_load * dst_capacity < dst_load * src_capacity;
+ else
+ /* Moving dst -> src. Did we overshoot balance? */
+ return dst_load * src_capacity < src_load * dst_capacity;
}

/*
@@ -1673,7 +1686,7 @@ static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
*period = now - p->last_task_numa_placement;
} else {
delta = p->se.avg.runnable_avg_sum;
- *period = p->se.avg.runnable_avg_period;
+ *period = p->se.avg.avg_period;
}

p->last_sum_exec_runtime = runtime;
@@ -1763,6 +1776,8 @@ static int preferred_group_nid(struct task_struct *p, int nid)
}
}
/* Next round, evaluate the nodes within max_group. */
+ if (!max_faults)
+ break;
nodes = max_group;
}
return nid;
@@ -2497,13 +2512,15 @@ static u32 __compute_runnable_contrib(u64 n)
* load_avg = u_0` + y*(u_0 + u_1*y + u_2*y^2 + ... )
* = u_0 + u_1*y + u_2*y^2 + ... [re-labeling u_i --> u_{i+1}]
*/
-static __always_inline int __update_entity_runnable_avg(u64 now,
+static __always_inline int __update_entity_runnable_avg(u64 now, int cpu,
struct sched_avg *sa,
- int runnable)
+ int runnable,
+ int running)
{
u64 delta, periods;
u32 runnable_contrib;
int delta_w, decayed = 0;
+ unsigned long scale_freq = arch_scale_freq_capacity(NULL, cpu);

delta = now - sa->last_runnable_update;
/*
@@ -2525,7 +2542,7 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
sa->last_runnable_update = now;

/* delta_w is the amount already accumulated against our next period */
- delta_w = sa->runnable_avg_period % 1024;
+ delta_w = sa->avg_period % 1024;
if (delta + delta_w >= 1024) {
/* period roll-over */
decayed = 1;
@@ -2538,7 +2555,10 @@ static __always_inline int __update_entity_runnable_avg(u64 now,
delta_w = 1024 - delta_w;
if (runnable)
sa->runnable_avg_sum += delta_w;
- sa->runnable_avg_period += delta_w;
+ if (running)
+ sa->running_avg_sum += delta_w * scale_freq
+ >> SCHED_CAPACITY_SHIFT;
+ sa->avg_period += delta_w;

delta -= delta_w;

@@ -2548,20 +2568,28 @@ static __always_inline int __update_entity_runnable_avg(u64 now,

sa->runnable_avg_sum = decay_load(sa->runnable_avg_sum,
periods + 1);
- sa->runnable_avg_period = decay_load(sa->runnable_avg_period,
+ sa->running_avg_sum = decay_load(sa->running_avg_sum,
+ periods + 1);
+ sa->avg_period = decay_load(sa->avg_period,
periods + 1);

/* Efficiently calculate \sum (1..n_period) 1024*y^i */
runnable_contrib = __compute_runnable_contrib(periods);
if (runnable)
sa->runnable_avg_sum += runnable_contrib;
- sa->runnable_avg_period += runnable_contrib;
+ if (running)
+ sa->running_avg_sum += runnable_contrib * scale_freq
+ >> SCHED_CAPACITY_SHIFT;
+ sa->avg_period += runnable_contrib;
}

/* Remainder of delta accrued against u_0` */
if (runnable)
sa->runnable_avg_sum += delta;
- sa->runnable_avg_period += delta;
+ if (running)
+ sa->running_avg_sum += delta * scale_freq
+ >> SCHED_CAPACITY_SHIFT;
+ sa->avg_period += delta;

return decayed;
}
@@ -2578,6 +2606,8 @@ static inline u64 __synchronize_entity_decay(struct sched_entity *se)
return 0;

se->avg.load_avg_contrib = decay_load(se->avg.load_avg_contrib, decays);
+ se->avg.utilization_avg_contrib =
+ decay_load(se->avg.utilization_avg_contrib, decays);

return decays;
}
@@ -2613,7 +2643,7 @@ static inline void __update_tg_runnable_avg(struct sched_avg *sa,

/* The fraction of a cpu used by this cfs_rq */
contrib = div_u64((u64)sa->runnable_avg_sum << NICE_0_SHIFT,
- sa->runnable_avg_period + 1);
+ sa->avg_period + 1);
contrib -= cfs_rq->tg_runnable_contrib;

if (abs(contrib) > cfs_rq->tg_runnable_contrib / 64) {
@@ -2666,7 +2696,8 @@ static inline void __update_group_entity_contrib(struct sched_entity *se)

static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
{
- __update_entity_runnable_avg(rq_clock_task(rq), &rq->avg, runnable);
+ __update_entity_runnable_avg(rq_clock_task(rq), cpu_of(rq), &rq->avg,
+ runnable, runnable);
__update_tg_runnable_avg(&rq->avg, &rq->cfs);
}
#else /* CONFIG_FAIR_GROUP_SCHED */
@@ -2684,7 +2715,7 @@ static inline void __update_task_entity_contrib(struct sched_entity *se)

/* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
contrib = se->avg.runnable_avg_sum * scale_load_down(se->load.weight);
- contrib /= (se->avg.runnable_avg_period + 1);
+ contrib /= (se->avg.avg_period + 1);
se->avg.load_avg_contrib = scale_load(contrib);
}

@@ -2703,6 +2734,30 @@ static long __update_entity_load_avg_contrib(struct sched_entity *se)
return se->avg.load_avg_contrib - old_contrib;
}

+
+static inline void __update_task_entity_utilization(struct sched_entity *se)
+{
+ u32 contrib;
+
+ /* avoid overflowing a 32-bit type w/ SCHED_LOAD_SCALE */
+ contrib = se->avg.running_avg_sum * scale_load_down(SCHED_LOAD_SCALE);
+ contrib /= (se->avg.avg_period + 1);
+ se->avg.utilization_avg_contrib = scale_load(contrib);
+}
+
+static long __update_entity_utilization_avg_contrib(struct sched_entity *se)
+{
+ long old_contrib = se->avg.utilization_avg_contrib;
+
+ if (entity_is_task(se))
+ __update_task_entity_utilization(se);
+ else
+ se->avg.utilization_avg_contrib =
+ group_cfs_rq(se)->utilization_load_avg;
+
+ return se->avg.utilization_avg_contrib - old_contrib;
+}
+
static inline void subtract_blocked_load_contrib(struct cfs_rq *cfs_rq,
long load_contrib)
{
@@ -2719,7 +2774,8 @@ static inline void update_entity_load_avg(struct sched_entity *se,
int update_cfs_rq)
{
struct cfs_rq *cfs_rq = cfs_rq_of(se);
- long contrib_delta;
+ long contrib_delta, utilization_delta;
+ int cpu = cpu_of(rq_of(cfs_rq));
u64 now;

/*
@@ -2731,18 +2787,22 @@ static inline void update_entity_load_avg(struct sched_entity *se,
else
now = cfs_rq_clock_task(group_cfs_rq(se));

- if (!__update_entity_runnable_avg(now, &se->avg, se->on_rq))
+ if (!__update_entity_runnable_avg(now, cpu, &se->avg, se->on_rq,
+ cfs_rq->curr == se))
return;

contrib_delta = __update_entity_load_avg_contrib(se);
+ utilization_delta = __update_entity_utilization_avg_contrib(se);

if (!update_cfs_rq)
return;

- if (se->on_rq)
+ if (se->on_rq) {
cfs_rq->runnable_load_avg += contrib_delta;
- else
+ cfs_rq->utilization_load_avg += utilization_delta;
+ } else {
subtract_blocked_load_contrib(cfs_rq, -contrib_delta);
+ }
}

/*
@@ -2817,6 +2877,7 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
}

cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
+ cfs_rq->utilization_load_avg += se->avg.utilization_avg_contrib;
/* we force update consideration on load-balancer moves */
update_cfs_rq_blocked_load(cfs_rq, !wakeup);
}
@@ -2835,6 +2896,7 @@ static inline void dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
update_cfs_rq_blocked_load(cfs_rq, !sleep);

cfs_rq->runnable_load_avg -= se->avg.load_avg_contrib;
+ cfs_rq->utilization_load_avg -= se->avg.utilization_avg_contrib;
if (sleep) {
cfs_rq->blocked_load_avg += se->avg.load_avg_contrib;
se->avg.decay_count = atomic64_read(&cfs_rq->decay_counter);
@@ -3172,6 +3234,7 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
*/
update_stats_wait_end(cfs_rq, se);
__dequeue_entity(cfs_rq, se);
+ update_entity_load_avg(se, 1);
}

update_stats_curr_start(cfs_rq, se);
@@ -4298,6 +4361,11 @@ static unsigned long capacity_of(int cpu)
return cpu_rq(cpu)->cpu_capacity;
}

+static unsigned long capacity_orig_of(int cpu)
+{
+ return cpu_rq(cpu)->cpu_capacity_orig;
+}
+
static unsigned long cpu_avg_load_per_task(int cpu)
{
struct rq *rq = cpu_rq(cpu);
@@ -4711,6 +4779,33 @@ static int select_idle_sibling(struct task_struct *p, int target)
done:
return target;
}
+/*
+ * get_cpu_usage returns the amount of capacity of a CPU that is used by CFS
+ * tasks. The unit of the return value must be the one of capacity so we can
+ * compare the usage with the capacity of the CPU that is available for CFS
+ * task (ie cpu_capacity).
+ * cfs.utilization_load_avg is the sum of running time of runnable tasks on a
+ * CPU. It represents the amount of utilization of a CPU in the range
+ * [0..SCHED_LOAD_SCALE]. The usage of a CPU can't be higher than the full
+ * capacity of the CPU because it's about the running time on this CPU.
+ * Nevertheless, cfs.utilization_load_avg can be higher than SCHED_LOAD_SCALE
+ * because of unfortunate rounding in avg_period and running_load_avg or just
+ * after migrating tasks until the average stabilizes with the new running
+ * time. So we need to check that the usage stays into the range
+ * [0..cpu_capacity_orig] and cap if necessary.
+ * Without capping the usage, a group could be seen as overloaded (CPU0 usage
+ * at 121% + CPU1 usage at 80%) whereas CPU1 has 20% of available capacity
+ */
+static int get_cpu_usage(int cpu)
+{
+ unsigned long usage = cpu_rq(cpu)->cfs.utilization_load_avg;
+ unsigned long capacity = capacity_orig_of(cpu);
+
+ if (usage >= SCHED_LOAD_SCALE)
+ return capacity;
+
+ return (usage * capacity) >> SCHED_LOAD_SHIFT;
+}

/*
* select_task_rq_fair: Select target runqueue for the waking task in domains
@@ -5837,12 +5932,12 @@ struct sg_lb_stats {
unsigned long sum_weighted_load; /* Weighted load of group's tasks */
unsigned long load_per_task;
unsigned long group_capacity;
+ unsigned long group_usage; /* Total usage of the group */
unsigned int sum_nr_running; /* Nr tasks running in the group */
- unsigned int group_capacity_factor;
unsigned int idle_cpus;
unsigned int group_weight;
enum group_type group_type;
- int group_has_free_capacity;
+ int group_no_capacity;
#ifdef CONFIG_NUMA_BALANCING
unsigned int nr_numa_running;
unsigned int nr_preferred_running;
@@ -5913,16 +6008,6 @@ static inline int get_sd_load_idx(struct sched_domain *sd,
return load_idx;
}

-static unsigned long default_scale_capacity(struct sched_domain *sd, int cpu)
-{
- return SCHED_CAPACITY_SCALE;
-}
-
-unsigned long __weak arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
-{
- return default_scale_capacity(sd, cpu);
-}
-
static unsigned long default_scale_cpu_capacity(struct sched_domain *sd, int cpu)
{
if ((sd->flags & SD_SHARE_CPUCAPACITY) && (sd->span_weight > 1))
@@ -5939,7 +6024,7 @@ unsigned long __weak arch_scale_cpu_capacity(struct sched_domain *sd, int cpu)
static unsigned long scale_rt_capacity(int cpu)
{
struct rq *rq = cpu_rq(cpu);
- u64 total, available, age_stamp, avg;
+ u64 total, used, age_stamp, avg;
s64 delta;

/*
@@ -5955,19 +6040,12 @@ static unsigned long scale_rt_capacity(int cpu)

total = sched_avg_period() + delta;

- if (unlikely(total < avg)) {
- /* Ensures that capacity won't end up being negative */
- available = 0;
- } else {
- available = total - avg;
- }
+ used = div_u64(avg, total);

- if (unlikely((s64)total < SCHED_CAPACITY_SCALE))
- total = SCHED_CAPACITY_SCALE;
+ if (likely(used < SCHED_CAPACITY_SCALE))
+ return SCHED_CAPACITY_SCALE - used;

- total >>= SCHED_CAPACITY_SHIFT;
-
- return div_u64(available, total);
+ return 1;
}

static void update_cpu_capacity(struct sched_domain *sd, int cpu)
@@ -5982,14 +6060,7 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu)

capacity >>= SCHED_CAPACITY_SHIFT;

- sdg->sgc->capacity_orig = capacity;
-
- if (sched_feat(ARCH_CAPACITY))
- capacity *= arch_scale_freq_capacity(sd, cpu);
- else
- capacity *= default_scale_capacity(sd, cpu);
-
- capacity >>= SCHED_CAPACITY_SHIFT;
+ cpu_rq(cpu)->cpu_capacity_orig = capacity;

capacity *= scale_rt_capacity(cpu);
capacity >>= SCHED_CAPACITY_SHIFT;
@@ -6005,7 +6076,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
{
struct sched_domain *child = sd->child;
struct sched_group *group, *sdg = sd->groups;
- unsigned long capacity, capacity_orig;
+ unsigned long capacity;
unsigned long interval;

interval = msecs_to_jiffies(sd->balance_interval);
@@ -6017,7 +6088,7 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
return;
}

- capacity_orig = capacity = 0;
+ capacity = 0;

if (child->flags & SD_OVERLAP) {
/*
@@ -6037,19 +6108,15 @@ void update_group_capacity(struct sched_domain *sd, int cpu)
* Use capacity_of(), which is set irrespective of domains
* in update_cpu_capacity().
*
- * This avoids capacity/capacity_orig from being 0 and
+ * This avoids capacity from being 0 and
* causing divide-by-zero issues on boot.
- *
- * Runtime updates will correct capacity_orig.
*/
if (unlikely(!rq->sd)) {
- capacity_orig += capacity_of(cpu);
capacity += capacity_of(cpu);
continue;
}

sgc = rq->sd->groups->sgc;
- capacity_orig += sgc->capacity_orig;
capacity += sgc->capacity;
}
} else {
@@ -6060,39 +6127,24 @@ void update_group_capacity(struct sched_domain *sd, int cpu)

group = child->groups;
do {
- capacity_orig += group->sgc->capacity_orig;
capacity += group->sgc->capacity;
group = group->next;
} while (group != child->groups);
}

- sdg->sgc->capacity_orig = capacity_orig;
sdg->sgc->capacity = capacity;
}

/*
- * Try and fix up capacity for tiny siblings, this is needed when
- * things like SD_ASYM_PACKING need f_b_g to select another sibling
- * which on its own isn't powerful enough.
- *
- * See update_sd_pick_busiest() and check_asym_packing().
+ * Check whether the capacity of the rq has been noticeably reduced by side
+ * activity. The imbalance_pct is used for the threshold.
+ * Return true is the capacity is reduced
*/
static inline int
-fix_small_capacity(struct sched_domain *sd, struct sched_group *group)
+check_cpu_capacity(struct rq *rq, struct sched_domain *sd)
{
- /*
- * Only siblings can have significantly less than SCHED_CAPACITY_SCALE
- */
- if (!(sd->flags & SD_SHARE_CPUCAPACITY))
- return 0;
-
- /*
- * If ~90% of the cpu_capacity is still there, we're good.
- */
- if (group->sgc->capacity * 32 > group->sgc->capacity_orig * 29)
- return 1;
-
- return 0;
+ return ((rq->cpu_capacity * sd->imbalance_pct) <
+ (rq->cpu_capacity_orig * 100));
}

/*
@@ -6130,37 +6182,56 @@ static inline int sg_imbalanced(struct sched_group *group)
}

/*
- * Compute the group capacity factor.
- *
- * Avoid the issue where N*frac(smt_capacity) >= 1 creates 'phantom' cores by
- * first dividing out the smt factor and computing the actual number of cores
- * and limit unit capacity with that.
+ * group_has_capacity returns true if the group has spare capacity that could
+ * be used by some tasks.
+ * We consider that a group has spare capacity if the * number of task is
+ * smaller than the number of CPUs or if the usage is lower than the available
+ * capacity for CFS tasks.
+ * For the latter, we use a threshold to stabilize the state, to take into
+ * account the variance of the tasks' load and to return true if the available
+ * capacity in meaningful for the load balancer.
+ * As an example, an available capacity of 1% can appear but it doesn't make
+ * any benefit for the load balance.
*/
-static inline int sg_capacity_factor(struct lb_env *env, struct sched_group *group)
+static inline bool
+group_has_capacity(struct lb_env *env, struct sg_lb_stats *sgs)
{
- unsigned int capacity_factor, smt, cpus;
- unsigned int capacity, capacity_orig;
+ if (sgs->sum_nr_running < sgs->group_weight)
+ return true;

- capacity = group->sgc->capacity;
- capacity_orig = group->sgc->capacity_orig;
- cpus = group->group_weight;
+ if ((sgs->group_capacity * 100) >
+ (sgs->group_usage * env->sd->imbalance_pct))
+ return true;

- /* smt := ceil(cpus / capacity), assumes: 1 < smt_capacity < 2 */
- smt = DIV_ROUND_UP(SCHED_CAPACITY_SCALE * cpus, capacity_orig);
- capacity_factor = cpus / smt; /* cores */
+ return false;
+}
+
+/*
+ * group_is_overloaded returns true if the group has more tasks than it can
+ * handle.
+ * group_is_overloaded is not equals to !group_has_capacity because a group
+ * with the exact right number of tasks, has no more spare capacity but is not
+ * overloaded so both group_has_capacity and group_is_overloaded return
+ * false.
+ */
+static inline bool
+group_is_overloaded(struct lb_env *env, struct sg_lb_stats *sgs)
+{
+ if (sgs->sum_nr_running <= sgs->group_weight)
+ return false;

- capacity_factor = min_t(unsigned,
- capacity_factor, DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE));
- if (!capacity_factor)
- capacity_factor = fix_small_capacity(env->sd, group);
+ if ((sgs->group_capacity * 100) <
+ (sgs->group_usage * env->sd->imbalance_pct))
+ return true;

- return capacity_factor;
+ return false;
}

-static enum group_type
-group_classify(struct sched_group *group, struct sg_lb_stats *sgs)
+static enum group_type group_classify(struct lb_env *env,
+ struct sched_group *group,
+ struct sg_lb_stats *sgs)
{
- if (sgs->sum_nr_running > sgs->group_capacity_factor)
+ if (sgs->group_no_capacity)
return group_overloaded;

if (sg_imbalanced(group))
@@ -6198,6 +6269,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
load = source_load(i, load_idx);

sgs->group_load += load;
+ sgs->group_usage += get_cpu_usage(i);
sgs->sum_nr_running += rq->cfs.h_nr_running;

if (rq->nr_running > 1)
@@ -6220,11 +6292,9 @@ static inline void update_sg_lb_stats(struct lb_env *env,
sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;

sgs->group_weight = group->group_weight;
- sgs->group_capacity_factor = sg_capacity_factor(env, group);
- sgs->group_type = group_classify(group, sgs);

- if (sgs->group_capacity_factor > sgs->sum_nr_running)
- sgs->group_has_free_capacity = 1;
+ sgs->group_no_capacity = group_is_overloaded(env, sgs);
+ sgs->group_type = group_classify(env, group, sgs);
}

/**
@@ -6346,18 +6416,19 @@ static inline void update_sd_lb_stats(struct lb_env *env, struct sd_lb_stats *sd

/*
* In case the child domain prefers tasks go to siblings
- * first, lower the sg capacity factor to one so that we'll try
+ * first, lower the sg capacity so that we'll try
* and move all the excess tasks away. We lower the capacity
* of a group only if the local group has the capacity to fit
- * these excess tasks, i.e. nr_running < group_capacity_factor. The
- * extra check prevents the case where you always pull from the
- * heaviest group when it is already under-utilized (possible
- * with a large weight task outweighs the tasks on the system).
+ * these excess tasks. The extra check prevents the case where
+ * you always pull from the heaviest group when it is already
+ * under-utilized (possible with a large weight task outweighs
+ * the tasks on the system).
*/
if (prefer_sibling && sds->local &&
- sds->local_stat.group_has_free_capacity) {
- sgs->group_capacity_factor = min(sgs->group_capacity_factor, 1U);
- sgs->group_type = group_classify(sg, sgs);
+ group_has_capacity(env, &sds->local_stat) &&
+ (sgs->sum_nr_running > 1)) {
+ sgs->group_no_capacity = 1;
+ sgs->group_type = group_overloaded;
}

if (update_sd_pick_busiest(env, sds, sg, sgs)) {
@@ -6537,11 +6608,12 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
*/
if (busiest->group_type == group_overloaded &&
local->group_type == group_overloaded) {
- load_above_capacity =
- (busiest->sum_nr_running - busiest->group_capacity_factor);
-
- load_above_capacity *= (SCHED_LOAD_SCALE * SCHED_CAPACITY_SCALE);
- load_above_capacity /= busiest->group_capacity;
+ load_above_capacity = busiest->sum_nr_running *
+ SCHED_LOAD_SCALE;
+ if (load_above_capacity > busiest->group_capacity)
+ load_above_capacity -= busiest->group_capacity;
+ else
+ load_above_capacity = ~0UL;
}

/*
@@ -6604,6 +6676,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
local = &sds.local_stat;
busiest = &sds.busiest_stat;

+ /* ASYM feature bypasses nice load balance check */
if ((env->idle == CPU_IDLE || env->idle == CPU_NEWLY_IDLE) &&
check_asym_packing(env, &sds))
return sds.busiest;
@@ -6624,8 +6697,8 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
goto force_balance;

/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
- if (env->idle == CPU_NEWLY_IDLE && local->group_has_free_capacity &&
- !busiest->group_has_free_capacity)
+ if (env->idle == CPU_NEWLY_IDLE && group_has_capacity(env, local) &&
+ busiest->group_no_capacity)
goto force_balance;

/*
@@ -6684,7 +6757,7 @@ static struct rq *find_busiest_queue(struct lb_env *env,
int i;

for_each_cpu_and(i, sched_group_cpus(group), env->cpus) {
- unsigned long capacity, capacity_factor, wl;
+ unsigned long capacity, wl;
enum fbq_type rt;

rq = cpu_rq(i);
@@ -6713,9 +6786,6 @@ static struct rq *find_busiest_queue(struct lb_env *env,
continue;

capacity = capacity_of(i);
- capacity_factor = DIV_ROUND_CLOSEST(capacity, SCHED_CAPACITY_SCALE);
- if (!capacity_factor)
- capacity_factor = fix_small_capacity(env->sd, group);

wl = weighted_cpuload(i);

@@ -6723,7 +6793,9 @@ static struct rq *find_busiest_queue(struct lb_env *env,
* When comparing with imbalance, use weighted_cpuload()
* which is not scaled with the cpu capacity.
*/
- if (capacity_factor && rq->nr_running == 1 && wl > env->imbalance)
+
+ if (rq->nr_running == 1 && wl > env->imbalance &&
+ !check_cpu_capacity(rq, env->sd))
continue;

/*
@@ -6771,6 +6843,19 @@ static int need_active_balance(struct lb_env *env)
return 1;
}

+ /*
+ * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
+ * It's worth migrating the task if the src_cpu's capacity is reduced
+ * because of other sched_class or IRQs if more capacity stays
+ * available on dst_cpu.
+ */
+ if ((env->idle != CPU_NOT_IDLE) &&
+ (env->src_rq->cfs.h_nr_running == 1)) {
+ if ((check_cpu_capacity(env->src_rq, sd)) &&
+ (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
+ return 1;
+ }
+
return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
}

@@ -6870,6 +6955,9 @@ static int load_balance(int this_cpu, struct rq *this_rq,

schedstat_add(sd, lb_imbalance[idle], env.imbalance);

+ env.src_cpu = busiest->cpu;
+ env.src_rq = busiest;
+
ld_moved = 0;
if (busiest->nr_running > 1) {
/*
@@ -6879,8 +6967,6 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* correctly treated as an imbalance.
*/
env.flags |= LBF_ALL_PINNED;
- env.src_cpu = busiest->cpu;
- env.src_rq = busiest;
env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);

more_balance:
@@ -7580,22 +7666,25 @@ static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle)

/*
* Current heuristic for kicking the idle load balancer in the presence
- * of an idle cpu is the system.
+ * of an idle cpu in the system.
* - This rq has more than one task.
- * - At any scheduler domain level, this cpu's scheduler group has multiple
- * busy cpu's exceeding the group's capacity.
+ * - This rq has at least one CFS task and the capacity of the CPU is
+ * significantly reduced because of RT tasks or IRQs.
+ * - At parent of LLC scheduler domain level, this cpu's scheduler group has
+ * multiple busy cpu.
* - For SD_ASYM_PACKING, if the lower numbered cpu's in the scheduler
* domain span are idle.
*/
-static inline int nohz_kick_needed(struct rq *rq)
+static inline bool nohz_kick_needed(struct rq *rq)
{
unsigned long now = jiffies;
struct sched_domain *sd;
struct sched_group_capacity *sgc;
int nr_busy, cpu = rq->cpu;
+ bool kick = false;

if (unlikely(rq->idle_balance))
- return 0;
+ return false;

/*
* We may be recently in ticked or tickless idle mode. At the first
@@ -7609,38 +7698,46 @@ static inline int nohz_kick_needed(struct rq *rq)
* balancing.
*/
if (likely(!atomic_read(&nohz.nr_cpus)))
- return 0;
+ return false;

if (time_before(now, nohz.next_balance))
- return 0;
+ return false;

if (rq->nr_running >= 2)
- goto need_kick;
+ return true;

rcu_read_lock();
sd = rcu_dereference(per_cpu(sd_busy, cpu));
-
if (sd) {
sgc = sd->groups->sgc;
nr_busy = atomic_read(&sgc->nr_busy_cpus);

- if (nr_busy > 1)
- goto need_kick_unlock;
+ if (nr_busy > 1) {
+ kick = true;
+ goto unlock;
+ }
+
}

- sd = rcu_dereference(per_cpu(sd_asym, cpu));
+ sd = rcu_dereference(rq->sd);
+ if (sd) {
+ if ((rq->cfs.h_nr_running >= 1) &&
+ check_cpu_capacity(rq, sd)) {
+ kick = true;
+ goto unlock;
+ }
+ }

+ sd = rcu_dereference(per_cpu(sd_asym, cpu));
if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
- sched_domain_span(sd)) < cpu))
- goto need_kick_unlock;
-
- rcu_read_unlock();
- return 0;
+ sched_domain_span(sd)) < cpu)) {
+ kick = true;
+ goto unlock;
+ }

-need_kick_unlock:
+unlock:
rcu_read_unlock();
-need_kick:
- return 1;
+ return kick;
}
#else
static void nohz_idle_balance(struct rq *this_rq, enum cpu_idle_type idle) { }
@@ -7656,14 +7753,16 @@ static void run_rebalance_domains(struct softirq_action *h)
enum cpu_idle_type idle = this_rq->idle_balance ?
CPU_IDLE : CPU_NOT_IDLE;

- rebalance_domains(this_rq, idle);
-
/*
* If this cpu has a pending nohz_balance_kick, then do the
* balancing on behalf of the other idle cpus whose ticks are
- * stopped.
+ * stopped. Do nohz_idle_balance *before* rebalance_domains to
+ * give the idle cpus a chance to load balance. Else we may
+ * load balance only within the local sched_domain hierarchy
+ * and abort nohz_idle_balance altogether if we pull some load.
*/
nohz_idle_balance(this_rq, idle);
+ rebalance_domains(this_rq, idle);
}

/*
diff --git a/kernel/sched/features.h b/kernel/sched/features.h
index 90284d117fe6..91e33cd485f6 100644
--- a/kernel/sched/features.h
+++ b/kernel/sched/features.h
@@ -56,6 +56,19 @@ SCHED_FEAT(NONTASK_CAPACITY, true)
*/
SCHED_FEAT(TTWU_QUEUE, true)

+#ifdef HAVE_RT_PUSH_IPI
+/*
+ * In order to avoid a thundering herd attack of CPUs that are
+ * lowering their priorities at the same time, and there being
+ * a single CPU that has an RT task that can migrate and is waiting
+ * to run, where the other CPUs will try to take that CPUs
+ * rq lock and possibly create a large contention, sending an
+ * IPI to that CPU and let that CPU push the RT task to where
+ * it should go may be a better scenario.
+ */
+SCHED_FEAT(RT_PUSH_IPI, true)
+#endif
+
SCHED_FEAT(FORCE_SD_OVERLAP, false)
SCHED_FEAT(RT_RUNTIME_SHARE, true)
SCHED_FEAT(LB_MIN, false)
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index f4d4b077eba0..575da76a3874 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -6,6 +6,7 @@
#include "sched.h"

#include <linux/slab.h>
+#include <linux/irq_work.h>

int sched_rr_timeslice = RR_TIMESLICE;

@@ -59,7 +60,11 @@ static void start_rt_bandwidth(struct rt_bandwidth *rt_b)
raw_spin_unlock(&rt_b->rt_runtime_lock);
}

-void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
+#ifdef CONFIG_SMP
+static void push_irq_work_func(struct irq_work *work);
+#endif
+
+void init_rt_rq(struct rt_rq *rt_rq)
{
struct rt_prio_array *array;
int i;
@@ -78,7 +83,14 @@ void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq)
rt_rq->rt_nr_migratory = 0;
rt_rq->overloaded = 0;
plist_head_init(&rt_rq->pushable_tasks);
+
+#ifdef HAVE_RT_PUSH_IPI
+ rt_rq->push_flags = 0;
+ rt_rq->push_cpu = nr_cpu_ids;
+ raw_spin_lock_init(&rt_rq->push_lock);
+ init_irq_work(&rt_rq->push_work, push_irq_work_func);
#endif
+#endif /* CONFIG_SMP */
/* We start is dequeued state, because no RT tasks are queued */
rt_rq->rt_queued = 0;

@@ -193,7 +205,7 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
if (!rt_se)
goto err_free_rq;

- init_rt_rq(rt_rq, cpu_rq(i));
+ init_rt_rq(rt_rq);
rt_rq->rt_runtime = tg->rt_bandwidth.rt_runtime;
init_tg_rt_entry(tg, rt_rq, rt_se, i, parent->rt_se[i]);
}
@@ -1778,6 +1790,164 @@ static void push_rt_tasks(struct rq *rq)
;
}

+#ifdef HAVE_RT_PUSH_IPI
+/*
+ * The search for the next cpu always starts at rq->cpu and ends
+ * when we reach rq->cpu again. It will never return rq->cpu.
+ * This returns the next cpu to check, or nr_cpu_ids if the loop
+ * is complete.
+ *
+ * rq->rt.push_cpu holds the last cpu returned by this function,
+ * or if this is the first instance, it must hold rq->cpu.
+ */
+static int rto_next_cpu(struct rq *rq)
+{
+ int prev_cpu = rq->rt.push_cpu;
+ int cpu;
+
+ cpu = cpumask_next(prev_cpu, rq->rd->rto_mask);
+
+ /*
+ * If the previous cpu is less than the rq's CPU, then it already
+ * passed the end of the mask, and has started from the beginning.
+ * We end if the next CPU is greater or equal to rq's CPU.
+ */
+ if (prev_cpu < rq->cpu) {
+ if (cpu >= rq->cpu)
+ return nr_cpu_ids;
+
+ } else if (cpu >= nr_cpu_ids) {
+ /*
+ * We passed the end of the mask, start at the beginning.
+ * If the result is greater or equal to the rq's CPU, then
+ * the loop is finished.
+ */
+ cpu = cpumask_first(rq->rd->rto_mask);
+ if (cpu >= rq->cpu)
+ return nr_cpu_ids;
+ }
+ rq->rt.push_cpu = cpu;
+
+ /* Return cpu to let the caller know if the loop is finished or not */
+ return cpu;
+}
+
+static int find_next_push_cpu(struct rq *rq)
+{
+ struct rq *next_rq;
+ int cpu;
+
+ while (1) {
+ cpu = rto_next_cpu(rq);
+ if (cpu >= nr_cpu_ids)
+ break;
+ next_rq = cpu_rq(cpu);
+
+ /* Make sure the next rq can push to this rq */
+ if (next_rq->rt.highest_prio.next < rq->rt.highest_prio.curr)
+ break;
+ }
+
+ return cpu;
+}
+
+#define RT_PUSH_IPI_EXECUTING 1
+#define RT_PUSH_IPI_RESTART 2
+
+static void tell_cpu_to_push(struct rq *rq)
+{
+ int cpu;
+
+ if (rq->rt.push_flags & RT_PUSH_IPI_EXECUTING) {
+ raw_spin_lock(&rq->rt.push_lock);
+ /* Make sure it's still executing */
+ if (rq->rt.push_flags & RT_PUSH_IPI_EXECUTING) {
+ /*
+ * Tell the IPI to restart the loop as things have
+ * changed since it started.
+ */
+ rq->rt.push_flags |= RT_PUSH_IPI_RESTART;
+ raw_spin_unlock(&rq->rt.push_lock);
+ return;
+ }
+ raw_spin_unlock(&rq->rt.push_lock);
+ }
+
+ /* When here, there's no IPI going around */
+
+ rq->rt.push_cpu = rq->cpu;
+ cpu = find_next_push_cpu(rq);
+ if (cpu >= nr_cpu_ids)
+ return;
+
+ rq->rt.push_flags = RT_PUSH_IPI_EXECUTING;
+
+ irq_work_queue_on(&rq->rt.push_work, cpu);
+}
+
+/* Called from hardirq context */
+static void try_to_push_tasks(void *arg)
+{
+ struct rt_rq *rt_rq = arg;
+ struct rq *rq, *src_rq;
+ int this_cpu;
+ int cpu;
+
+ this_cpu = rt_rq->push_cpu;
+
+ /* Paranoid check */
+ BUG_ON(this_cpu != smp_processor_id());
+
+ rq = cpu_rq(this_cpu);
+ src_rq = rq_of_rt_rq(rt_rq);
+
+again:
+ if (has_pushable_tasks(rq)) {
+ raw_spin_lock(&rq->lock);
+ push_rt_task(rq);
+ raw_spin_unlock(&rq->lock);
+ }
+
+ /* Pass the IPI to the next rt overloaded queue */
+ raw_spin_lock(&rt_rq->push_lock);
+ /*
+ * If the source queue changed since the IPI went out,
+ * we need to restart the search from that CPU again.
+ */
+ if (rt_rq->push_flags & RT_PUSH_IPI_RESTART) {
+ rt_rq->push_flags &= ~RT_PUSH_IPI_RESTART;
+ rt_rq->push_cpu = src_rq->cpu;
+ }
+
+ cpu = find_next_push_cpu(src_rq);
+
+ if (cpu >= nr_cpu_ids)
+ rt_rq->push_flags &= ~RT_PUSH_IPI_EXECUTING;
+ raw_spin_unlock(&rt_rq->push_lock);
+
+ if (cpu >= nr_cpu_ids)
+ return;
+
+ /*
+ * It is possible that a restart caused this CPU to be
+ * chosen again. Don't bother with an IPI, just see if we
+ * have more to push.
+ */
+ if (unlikely(cpu == rq->cpu))
+ goto again;
+
+ /* Try the next RT overloaded CPU */
+ irq_work_queue_on(&rt_rq->push_work, cpu);
+}
+
+static void push_irq_work_func(struct irq_work *work)
+{
+ struct rt_rq *rt_rq = container_of(work, struct rt_rq, push_work);
+
+ try_to_push_tasks(rt_rq);
+}
+#endif /* HAVE_RT_PUSH_IPI */
+
static int pull_rt_task(struct rq *this_rq)
{
int this_cpu = this_rq->cpu, ret = 0, cpu;
@@ -1793,6 +1963,13 @@ static int pull_rt_task(struct rq *this_rq)
*/
smp_rmb();

+#ifdef HAVE_RT_PUSH_IPI
+ if (sched_feat(RT_PUSH_IPI)) {
+ tell_cpu_to_push(this_rq);
+ return 0;
+ }
+#endif
+
for_each_cpu(cpu, this_rq->rd->rto_mask) {
if (this_cpu == cpu)
continue;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index dc0f435a2779..e0e129993958 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -6,6 +6,7 @@
#include <linux/mutex.h>
#include <linux/spinlock.h>
#include <linux/stop_machine.h>
+#include <linux/irq_work.h>
#include <linux/tick.h>
#include <linux/slab.h>

@@ -362,8 +363,14 @@ struct cfs_rq {
* Under CFS, load is tracked on a per-entity basis and aggregated up.
* This allows for the description of both thread and group usage (in
* the FAIR_GROUP_SCHED case).
+ * runnable_load_avg is the sum of the load_avg_contrib of the
+ * sched_entities on the rq.
+ * blocked_load_avg is similar to runnable_load_avg except that its
+ * the blocked sched_entities on the rq.
+ * utilization_load_avg is the sum of the average running time of the
+ * sched_entities on the rq.
*/
- unsigned long runnable_load_avg, blocked_load_avg;
+ unsigned long runnable_load_avg, blocked_load_avg, utilization_load_avg;
atomic64_t decay_counter;
u64 last_decay;
atomic_long_t removed_load;
@@ -418,6 +425,11 @@ static inline int rt_bandwidth_enabled(void)
return sysctl_sched_rt_runtime >= 0;
}

+/* RT IPI pull logic requires IRQ_WORK */
+#ifdef CONFIG_IRQ_WORK
+# define HAVE_RT_PUSH_IPI
+#endif
+
/* Real-Time classes' related field in a runqueue: */
struct rt_rq {
struct rt_prio_array active;
@@ -435,7 +447,13 @@ struct rt_rq {
unsigned long rt_nr_total;
int overloaded;
struct plist_head pushable_tasks;
+#ifdef HAVE_RT_PUSH_IPI
+ int push_flags;
+ int push_cpu;
+ struct irq_work push_work;
+ raw_spinlock_t push_lock;
#endif
+#endif /* CONFIG_SMP */
int rt_queued;

int rt_throttled;
@@ -597,6 +615,7 @@ struct rq {
struct sched_domain *sd;

unsigned long cpu_capacity;
+ unsigned long cpu_capacity_orig;

unsigned char idle_balance;
/* For active balancing */
@@ -807,7 +826,7 @@ struct sched_group_capacity {
* CPU capacity of this group, SCHED_LOAD_SCALE being max capacity
* for a single CPU.
*/
- unsigned int capacity, capacity_orig;
+ unsigned int capacity;
unsigned long next_update;
int imbalance; /* XXX unrelated to capacity but shared group state */
/*
@@ -1368,9 +1387,18 @@ static inline int hrtick_enabled(struct rq *rq)

#ifdef CONFIG_SMP
extern void sched_avg_update(struct rq *rq);
+
+#ifndef arch_scale_freq_capacity
+static __always_inline
+unsigned long arch_scale_freq_capacity(struct sched_domain *sd, int cpu)
+{
+ return SCHED_CAPACITY_SCALE;
+}
+#endif
+
static inline void sched_rt_avg_update(struct rq *rq, u64 rt_delta)
{
- rq->rt_avg += rt_delta;
+ rq->rt_avg += rt_delta * arch_scale_freq_capacity(NULL, cpu_of(rq));
sched_avg_update(rq);
}
#else
@@ -1643,8 +1671,8 @@ extern void print_rt_stats(struct seq_file *m, int cpu);
extern void print_dl_stats(struct seq_file *m, int cpu);

extern void init_cfs_rq(struct cfs_rq *cfs_rq);
-extern void init_rt_rq(struct rt_rq *rt_rq, struct rq *rq);
-extern void init_dl_rq(struct dl_rq *dl_rq, struct rq *rq);
+extern void init_rt_rq(struct rt_rq *rt_rq);
+extern void init_dl_rq(struct dl_rq *dl_rq);

extern void cfs_bandwidth_usage_inc(void);
extern void cfs_bandwidth_usage_dec(void);

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