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Subject[GIT PULL] scheduler changes for v4.5
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: 0905f04eb21fc1c2e690bed5d0418a061d56c225 sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task()

The main changes in this cycle were:

- tickless load average calculation enhancements (Byungchul Park)

- vtime handling enhancements (Frederic Weisbecker)

- scalability improvement via properly aligning a key structure field (Jiri Olsa)

- various stop_machine() fixes (Oleg Nesterov)

- sched/numa enhancement (Rik van Riel)

- various fixes and improvements (Andi Kleen, Dietmar Eggemann, Geliang
Tang, Hiroshi Shimamoto, Joonwoo Park, Peter Zijlstra, Waiman Long,
Wanpeng Li, Yuyang Du)

Thanks,

Ingo

------------------>
Andi Kleen (1):
sched/core: Move the sched_to_prio[] arrays out of line

Byungchul Park (4):
sched/fair: Prepare __update_cpu_load() to handle active tickless
sched/fair: Consider missed ticks in NOHZ_FULL in update_cpu_load_nohz()
sched/fair: Modify the comment about lock assumptions in migrate_task_rq_fair()
sched/fair: Make it possible to account fair load avg consistently

Dietmar Eggemann (1):
sched/fair: Remove empty idle enter and exit functions

Frederic Weisbecker (5):
sched/cputime: Clarify vtime symbols and document them
sched/cputime: Correctly handle task guest time on housekeepers
sched/cputime: Rename vtime_accounting_enabled() to vtime_accounting_cpu_enabled()
sched/cputime: Introduce vtime accounting check for readers
sched/cputime: Convert vtime_seqlock to seqcount

Geliang Tang (1):
sched/core: Use list_is_singular() in sched_can_stop_tick()

Hiroshi Shimamoto (1):
sched/cputime: Remove extra cost in task_cputime()

Jiri Olsa (2):
x86/fpu: Properly align size in CHECK_MEMBER_AT_END_OF() macro
sched/core: Move sched_entity::avg into separate cache line

Joonwoo Park (1):
sched/core: Fix incorrect wait time and wait count statistics

Oleg Nesterov (8):
stop_machine: Fix possible cpu_stopper_thread() crash
stop_machine: Don't disable preemption in stop_two_cpus()
stop_machine: Make cpu_stop_queue_work() and stop_one_cpu_nowait() return bool
stop_machine: Change stop_one_cpu() to rely on cpu_stop_queue_work()
stop_machine: Change __stop_cpus() to rely on cpu_stop_queue_work()
stop_machine: Kill cpu_stop_done->executed
stop_machine: Shift the 'done != NULL' check from cpu_stop_signal_done() to callers
stop_machine: Clean up the usage of the preemption counter in cpu_stopper_thread()

Peter Zijlstra (2):
sched/wait: Document waitqueue_active()
sched/fair: Clean up the explanation around decaying load update misses

Rik van Riel (1):
sched/numa: Cap PTE scanning overhead to 3% of run time

Waiman Long (3):
sched/fair: Avoid redundant idle_cpu() call in update_sg_lb_stats()
sched/fair: Move the cache-hot 'load_avg' variable into its own cacheline
sched/fair: Disable the task group load_avg update for the root_task_group

Wanpeng Li (1):
sched/deadline: Fix the earliest_dl.next logic

Yuyang Du (1):
sched/fair: Fix new task's load avg removed from source CPU in wake_up_new_task()


arch/x86/kernel/fpu/init.c | 13 +-
include/linux/context_tracking.h | 4 +-
include/linux/init_task.h | 2 +-
include/linux/sched.h | 20 ++-
include/linux/stop_machine.h | 7 +-
include/linux/vtime.h | 25 +++-
include/linux/wait.h | 30 ++++
kernel/fork.c | 4 +-
kernel/sched/auto_group.c | 2 +-
kernel/sched/core.c | 76 +++++++++-
kernel/sched/cputime.c | 74 ++++++----
kernel/sched/deadline.c | 59 +-------
kernel/sched/fair.c | 312 +++++++++++++++++++++++++++------------
kernel/sched/idle_task.c | 1 -
kernel/sched/sched.h | 68 +++------
kernel/stop_machine.c | 84 +++++------
kernel/time/tick-sched.c | 10 +-
17 files changed, 485 insertions(+), 306 deletions(-)

diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c
index be39b5fde4b9..8e839e7f5e2f 100644
--- a/arch/x86/kernel/fpu/init.c
+++ b/arch/x86/kernel/fpu/init.c
@@ -143,9 +143,18 @@ static void __init fpu__init_system_generic(void)
unsigned int xstate_size;
EXPORT_SYMBOL_GPL(xstate_size);

-/* Enforce that 'MEMBER' is the last field of 'TYPE': */
+/* Get alignment of the TYPE. */
+#define TYPE_ALIGN(TYPE) offsetof(struct { char x; TYPE test; }, test)
+
+/*
+ * Enforce that 'MEMBER' is the last field of 'TYPE'.
+ *
+ * Align the computed size with alignment of the TYPE,
+ * because that's how C aligns structs.
+ */
#define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \
- BUILD_BUG_ON(sizeof(TYPE) != offsetofend(TYPE, MEMBER))
+ BUILD_BUG_ON(sizeof(TYPE) != ALIGN(offsetofend(TYPE, MEMBER), \
+ TYPE_ALIGN(TYPE)))

/*
* We append the 'struct fpu' to the task_struct:
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 68b575afe5f5..d259274238db 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -86,7 +86,7 @@ static inline void context_tracking_init(void) { }
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
static inline void guest_enter(void)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_guest_enter(current);
else
current->flags |= PF_VCPU;
@@ -100,7 +100,7 @@ static inline void guest_exit(void)
if (context_tracking_is_enabled())
__context_tracking_exit(CONTEXT_GUEST);

- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_guest_exit(current);
else
current->flags &= ~PF_VCPU;
diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 1c1ff7e4faa4..f2cb8d45513d 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -150,7 +150,7 @@ extern struct task_group root_task_group;

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
# define INIT_VTIME(tsk) \
- .vtime_seqlock = __SEQLOCK_UNLOCKED(tsk.vtime_seqlock), \
+ .vtime_seqcount = SEQCNT_ZERO(tsk.vtime_seqcount), \
.vtime_snap = 0, \
.vtime_snap_whence = VTIME_SYS,
#else
diff --git a/include/linux/sched.h b/include/linux/sched.h
index fa39434e3fdd..0c0e78102850 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -177,9 +177,9 @@ extern void get_iowait_load(unsigned long *nr_waiters, unsigned long *load);
extern void calc_global_load(unsigned long ticks);

#if defined(CONFIG_SMP) && defined(CONFIG_NO_HZ_COMMON)
-extern void update_cpu_load_nohz(void);
+extern void update_cpu_load_nohz(int active);
#else
-static inline void update_cpu_load_nohz(void) { }
+static inline void update_cpu_load_nohz(int active) { }
#endif

extern unsigned long get_parent_ip(unsigned long addr);
@@ -1268,8 +1268,13 @@ struct sched_entity {
#endif

#ifdef CONFIG_SMP
- /* Per entity load average tracking */
- struct sched_avg avg;
+ /*
+ * Per entity load average tracking.
+ *
+ * Put into separate cache line so it does not
+ * collide with read-mostly values above.
+ */
+ struct sched_avg avg ____cacheline_aligned_in_smp;
#endif
};

@@ -1520,11 +1525,14 @@ struct task_struct {
cputime_t gtime;
struct prev_cputime prev_cputime;
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
- seqlock_t vtime_seqlock;
+ seqcount_t vtime_seqcount;
unsigned long long vtime_snap;
enum {
- VTIME_SLEEPING = 0,
+ /* Task is sleeping or running in a CPU with VTIME inactive */
+ VTIME_INACTIVE = 0,
+ /* Task runs in userspace in a CPU with VTIME active */
VTIME_USER,
+ /* Task runs in kernelspace in a CPU with VTIME active */
VTIME_SYS,
} vtime_snap_whence;
#endif
diff --git a/include/linux/stop_machine.h b/include/linux/stop_machine.h
index 0e1b1540597a..3cc9632dcc2a 100644
--- a/include/linux/stop_machine.h
+++ b/include/linux/stop_machine.h
@@ -29,7 +29,7 @@ struct cpu_stop_work {

int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg);
int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *arg);
-void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf);
int stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
int try_stop_cpus(const struct cpumask *cpumask, cpu_stop_fn_t fn, void *arg);
@@ -65,7 +65,7 @@ static void stop_one_cpu_nowait_workfn(struct work_struct *work)
preempt_enable();
}

-static inline void stop_one_cpu_nowait(unsigned int cpu,
+static inline bool stop_one_cpu_nowait(unsigned int cpu,
cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
@@ -74,7 +74,10 @@ static inline void stop_one_cpu_nowait(unsigned int cpu,
work_buf->fn = fn;
work_buf->arg = arg;
schedule_work(&work_buf->work);
+ return true;
}
+
+ return false;
}

static inline int stop_cpus(const struct cpumask *cpumask,
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index c5165fd256f9..fa2196990f84 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -10,16 +10,27 @@
struct task_struct;

/*
- * vtime_accounting_enabled() definitions/declarations
+ * vtime_accounting_cpu_enabled() definitions/declarations
*/
#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
-static inline bool vtime_accounting_enabled(void) { return true; }
+static inline bool vtime_accounting_cpu_enabled(void) { return true; }
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
+/*
+ * Checks if vtime is enabled on some CPU. Cputime readers want to be careful
+ * in that case and compute the tickless cputime.
+ * For now vtime state is tied to context tracking. We might want to decouple
+ * those later if necessary.
+ */
static inline bool vtime_accounting_enabled(void)
{
- if (context_tracking_is_enabled()) {
+ return context_tracking_is_enabled();
+}
+
+static inline bool vtime_accounting_cpu_enabled(void)
+{
+ if (vtime_accounting_enabled()) {
if (context_tracking_cpu_is_enabled())
return true;
}
@@ -29,7 +40,7 @@ static inline bool vtime_accounting_enabled(void)
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_GEN */

#ifndef CONFIG_VIRT_CPU_ACCOUNTING
-static inline bool vtime_accounting_enabled(void) { return false; }
+static inline bool vtime_accounting_cpu_enabled(void) { return false; }
#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */


@@ -44,7 +55,7 @@ extern void vtime_task_switch(struct task_struct *prev);
extern void vtime_common_task_switch(struct task_struct *prev);
static inline void vtime_task_switch(struct task_struct *prev)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_common_task_switch(prev);
}
#endif /* __ARCH_HAS_VTIME_TASK_SWITCH */
@@ -59,7 +70,7 @@ extern void vtime_account_irq_enter(struct task_struct *tsk);
extern void vtime_common_account_irq_enter(struct task_struct *tsk);
static inline void vtime_account_irq_enter(struct task_struct *tsk)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_common_account_irq_enter(tsk);
}
#endif /* __ARCH_HAS_VTIME_ACCOUNT */
@@ -78,7 +89,7 @@ extern void vtime_gen_account_irq_exit(struct task_struct *tsk);

static inline void vtime_account_irq_exit(struct task_struct *tsk)
{
- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
vtime_gen_account_irq_exit(tsk);
}

diff --git a/include/linux/wait.h b/include/linux/wait.h
index 513b36f04dfd..d2f4ec7dba7c 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -102,6 +102,36 @@ init_waitqueue_func_entry(wait_queue_t *q, wait_queue_func_t func)
q->func = func;
}

+/**
+ * waitqueue_active -- locklessly test for waiters on the queue
+ * @q: the waitqueue to test for waiters
+ *
+ * returns true if the wait list is not empty
+ *
+ * NOTE: this function is lockless and requires care, incorrect usage _will_
+ * lead to sporadic and non-obvious failure.
+ *
+ * Use either while holding wait_queue_head_t::lock or when used for wakeups
+ * with an extra smp_mb() like:
+ *
+ * CPU0 - waker CPU1 - waiter
+ *
+ * for (;;) {
+ * @cond = true; prepare_to_wait(&wq, &wait, state);
+ * smp_mb(); // smp_mb() from set_current_state()
+ * if (waitqueue_active(wq)) if (@cond)
+ * wake_up(wq); break;
+ * schedule();
+ * }
+ * finish_wait(&wq, &wait);
+ *
+ * Because without the explicit smp_mb() it's possible for the
+ * waitqueue_active() load to get hoisted over the @cond store such that we'll
+ * observe an empty wait list while the waiter might not observe @cond.
+ *
+ * Also note that this 'optimization' trades a spin_lock() for an smp_mb(),
+ * which (when the lock is uncontended) are of roughly equal cost.
+ */
static inline int waitqueue_active(wait_queue_head_t *q)
{
return !list_empty(&q->task_list);
diff --git a/kernel/fork.c b/kernel/fork.c
index 1155eac61687..291b08cc817b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1349,9 +1349,9 @@ static struct task_struct *copy_process(unsigned long clone_flags,
prev_cputime_init(&p->prev_cputime);

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_GEN
- seqlock_init(&p->vtime_seqlock);
+ seqcount_init(&p->vtime_seqcount);
p->vtime_snap = 0;
- p->vtime_snap_whence = VTIME_SLEEPING;
+ p->vtime_snap_whence = VTIME_INACTIVE;
#endif

#if defined(SPLIT_RSS_COUNTING)
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index 750ed601ddf7..a5d966cb8891 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -212,7 +212,7 @@ int proc_sched_autogroup_set_nice(struct task_struct *p, int nice)
ag = autogroup_task_get(p);

down_write(&ag->lock);
- err = sched_group_set_shares(ag->tg, prio_to_weight[nice + 20]);
+ err = sched_group_set_shares(ag->tg, sched_prio_to_weight[nice + 20]);
if (!err)
ag->nice = nice;
up_write(&ag->lock);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 732e993b564b..1315cec45882 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -731,7 +731,7 @@ bool sched_can_stop_tick(void)
if (current->policy == SCHED_RR) {
struct sched_rt_entity *rt_se = &current->rt;

- return rt_se->run_list.prev == rt_se->run_list.next;
+ return list_is_singular(&rt_se->run_list);
}

/*
@@ -823,8 +823,8 @@ static void set_load_weight(struct task_struct *p)
return;
}

- load->weight = scale_load(prio_to_weight[prio]);
- load->inv_weight = prio_to_wmult[prio];
+ load->weight = scale_load(sched_prio_to_weight[prio]);
+ load->inv_weight = sched_prio_to_wmult[prio];
}

static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
@@ -1071,8 +1071,8 @@ static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new
{
lockdep_assert_held(&rq->lock);

- dequeue_task(rq, p, 0);
p->on_rq = TASK_ON_RQ_MIGRATING;
+ dequeue_task(rq, p, 0);
set_task_cpu(p, new_cpu);
raw_spin_unlock(&rq->lock);

@@ -1080,8 +1080,8 @@ static struct rq *move_queued_task(struct rq *rq, struct task_struct *p, int new

raw_spin_lock(&rq->lock);
BUG_ON(task_cpu(p) != new_cpu);
- p->on_rq = TASK_ON_RQ_QUEUED;
enqueue_task(rq, p, 0);
+ p->on_rq = TASK_ON_RQ_QUEUED;
check_preempt_curr(rq, p, 0);

return rq;
@@ -1274,6 +1274,15 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
!p->on_rq);

+ /*
+ * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING,
+ * because schedstat_wait_{start,end} rebase migrating task's wait_start
+ * time relying on p->on_rq.
+ */
+ WARN_ON_ONCE(p->state == TASK_RUNNING &&
+ p->sched_class == &fair_sched_class &&
+ (p->on_rq && !task_on_rq_migrating(p)));
+
#ifdef CONFIG_LOCKDEP
/*
* The caller should hold either p->pi_lock or rq->lock, when changing
@@ -1310,9 +1319,11 @@ static void __migrate_swap_task(struct task_struct *p, int cpu)
src_rq = task_rq(p);
dst_rq = cpu_rq(cpu);

+ p->on_rq = TASK_ON_RQ_MIGRATING;
deactivate_task(src_rq, p, 0);
set_task_cpu(p, cpu);
activate_task(dst_rq, p, 0);
+ p->on_rq = TASK_ON_RQ_QUEUED;
check_preempt_curr(dst_rq, p, 0);
} else {
/*
@@ -2109,6 +2120,10 @@ static void __sched_fork(unsigned long clone_flags, struct task_struct *p)
p->se.vruntime = 0;
INIT_LIST_HEAD(&p->se.group_node);

+#ifdef CONFIG_FAIR_GROUP_SCHED
+ p->se.cfs_rq = NULL;
+#endif
+
#ifdef CONFIG_SCHEDSTATS
memset(&p->se.statistics, 0, sizeof(p->se.statistics));
#endif
@@ -7355,6 +7370,9 @@ int in_sched_functions(unsigned long addr)
*/
struct task_group root_task_group;
LIST_HEAD(task_groups);
+
+/* Cacheline aligned slab cache for task_group */
+static struct kmem_cache *task_group_cache __read_mostly;
#endif

DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
@@ -7412,11 +7430,12 @@ void __init sched_init(void)
#endif /* CONFIG_RT_GROUP_SCHED */

#ifdef CONFIG_CGROUP_SCHED
+ task_group_cache = KMEM_CACHE(task_group, 0);
+
list_add(&root_task_group.list, &task_groups);
INIT_LIST_HEAD(&root_task_group.children);
INIT_LIST_HEAD(&root_task_group.siblings);
autogroup_init(&init_task);
-
#endif /* CONFIG_CGROUP_SCHED */

for_each_possible_cpu(i) {
@@ -7697,7 +7716,7 @@ static void free_sched_group(struct task_group *tg)
free_fair_sched_group(tg);
free_rt_sched_group(tg);
autogroup_free(tg);
- kfree(tg);
+ kmem_cache_free(task_group_cache, tg);
}

/* allocate runqueue etc for a new task group */
@@ -7705,7 +7724,7 @@ struct task_group *sched_create_group(struct task_group *parent)
{
struct task_group *tg;

- tg = kzalloc(sizeof(*tg), GFP_KERNEL);
+ tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO);
if (!tg)
return ERR_PTR(-ENOMEM);

@@ -8610,3 +8629,44 @@ void dump_cpu_task(int cpu)
pr_info("Task dump for CPU %d:\n", cpu);
sched_show_task(cpu_curr(cpu));
}
+
+/*
+ * Nice levels are multiplicative, with a gentle 10% change for every
+ * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
+ * nice 1, it will get ~10% less CPU time than another CPU-bound task
+ * that remained on nice 0.
+ *
+ * The "10% effect" is relative and cumulative: from _any_ nice level,
+ * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
+ * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
+ * If a task goes up by ~10% and another task goes down by ~10% then
+ * the relative distance between them is ~25%.)
+ */
+const int sched_prio_to_weight[40] = {
+ /* -20 */ 88761, 71755, 56483, 46273, 36291,
+ /* -15 */ 29154, 23254, 18705, 14949, 11916,
+ /* -10 */ 9548, 7620, 6100, 4904, 3906,
+ /* -5 */ 3121, 2501, 1991, 1586, 1277,
+ /* 0 */ 1024, 820, 655, 526, 423,
+ /* 5 */ 335, 272, 215, 172, 137,
+ /* 10 */ 110, 87, 70, 56, 45,
+ /* 15 */ 36, 29, 23, 18, 15,
+};
+
+/*
+ * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated.
+ *
+ * In cases where the weight does not change often, we can use the
+ * precalculated inverse to speed up arithmetics by turning divisions
+ * into multiplications:
+ */
+const u32 sched_prio_to_wmult[40] = {
+ /* -20 */ 48388, 59856, 76040, 92818, 118348,
+ /* -15 */ 147320, 184698, 229616, 287308, 360437,
+ /* -10 */ 449829, 563644, 704093, 875809, 1099582,
+ /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
+ /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
+ /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
+ /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
+ /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
+};
diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 05de80b48586..d5ff5c6bf829 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -466,7 +466,7 @@ void account_process_tick(struct task_struct *p, int user_tick)
cputime_t one_jiffy_scaled = cputime_to_scaled(cputime_one_jiffy);
struct rq *rq = this_rq();

- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
return;

if (sched_clock_irqtime) {
@@ -680,7 +680,7 @@ static cputime_t get_vtime_delta(struct task_struct *tsk)
{
unsigned long long delta = vtime_delta(tsk);

- WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_SLEEPING);
+ WARN_ON_ONCE(tsk->vtime_snap_whence == VTIME_INACTIVE);
tsk->vtime_snap += delta;

/* CHECKME: always safe to convert nsecs to cputime? */
@@ -696,37 +696,37 @@ static void __vtime_account_system(struct task_struct *tsk)

void vtime_account_system(struct task_struct *tsk)
{
- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
__vtime_account_system(tsk);
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}

void vtime_gen_account_irq_exit(struct task_struct *tsk)
{
- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
__vtime_account_system(tsk);
if (context_tracking_in_user())
tsk->vtime_snap_whence = VTIME_USER;
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}

void vtime_account_user(struct task_struct *tsk)
{
cputime_t delta_cpu;

- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
delta_cpu = get_vtime_delta(tsk);
tsk->vtime_snap_whence = VTIME_SYS;
account_user_time(tsk, delta_cpu, cputime_to_scaled(delta_cpu));
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}

void vtime_user_enter(struct task_struct *tsk)
{
- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
__vtime_account_system(tsk);
tsk->vtime_snap_whence = VTIME_USER;
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}

void vtime_guest_enter(struct task_struct *tsk)
@@ -738,19 +738,19 @@ void vtime_guest_enter(struct task_struct *tsk)
* synchronization against the reader (task_gtime())
* that can thus safely catch up with a tickless delta.
*/
- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
__vtime_account_system(tsk);
current->flags |= PF_VCPU;
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}
EXPORT_SYMBOL_GPL(vtime_guest_enter);

void vtime_guest_exit(struct task_struct *tsk)
{
- write_seqlock(&tsk->vtime_seqlock);
+ write_seqcount_begin(&tsk->vtime_seqcount);
__vtime_account_system(tsk);
current->flags &= ~PF_VCPU;
- write_sequnlock(&tsk->vtime_seqlock);
+ write_seqcount_end(&tsk->vtime_seqcount);
}
EXPORT_SYMBOL_GPL(vtime_guest_exit);

@@ -763,24 +763,26 @@ void vtime_account_idle(struct task_struct *tsk)

void arch_vtime_task_switch(struct task_struct *prev)
{
- write_seqlock(&prev->vtime_seqlock);
- prev->vtime_snap_whence = VTIME_SLEEPING;
- write_sequnlock(&prev->vtime_seqlock);
+ write_seqcount_begin(&prev->vtime_seqcount);
+ prev->vtime_snap_whence = VTIME_INACTIVE;
+ write_seqcount_end(&prev->vtime_seqcount);

- write_seqlock(&current->vtime_seqlock);
+ write_seqcount_begin(&current->vtime_seqcount);
current->vtime_snap_whence = VTIME_SYS;
current->vtime_snap = sched_clock_cpu(smp_processor_id());
- write_sequnlock(&current->vtime_seqlock);
+ write_seqcount_end(&current->vtime_seqcount);
}

void vtime_init_idle(struct task_struct *t, int cpu)
{
unsigned long flags;

- write_seqlock_irqsave(&t->vtime_seqlock, flags);
+ local_irq_save(flags);
+ write_seqcount_begin(&t->vtime_seqcount);
t->vtime_snap_whence = VTIME_SYS;
t->vtime_snap = sched_clock_cpu(cpu);
- write_sequnlock_irqrestore(&t->vtime_seqlock, flags);
+ write_seqcount_end(&t->vtime_seqcount);
+ local_irq_restore(flags);
}

cputime_t task_gtime(struct task_struct *t)
@@ -788,17 +790,17 @@ cputime_t task_gtime(struct task_struct *t)
unsigned int seq;
cputime_t gtime;

- if (!context_tracking_is_enabled())
+ if (!vtime_accounting_enabled())
return t->gtime;

do {
- seq = read_seqbegin(&t->vtime_seqlock);
+ seq = read_seqcount_begin(&t->vtime_seqcount);

gtime = t->gtime;
- if (t->flags & PF_VCPU)
+ if (t->vtime_snap_whence == VTIME_SYS && t->flags & PF_VCPU)
gtime += vtime_delta(t);

- } while (read_seqretry(&t->vtime_seqlock, seq));
+ } while (read_seqcount_retry(&t->vtime_seqcount, seq));

return gtime;
}
@@ -821,7 +823,7 @@ fetch_task_cputime(struct task_struct *t,
*udelta = 0;
*sdelta = 0;

- seq = read_seqbegin(&t->vtime_seqlock);
+ seq = read_seqcount_begin(&t->vtime_seqcount);

if (u_dst)
*u_dst = *u_src;
@@ -829,7 +831,7 @@ fetch_task_cputime(struct task_struct *t,
*s_dst = *s_src;

/* Task is sleeping, nothing to add */
- if (t->vtime_snap_whence == VTIME_SLEEPING ||
+ if (t->vtime_snap_whence == VTIME_INACTIVE ||
is_idle_task(t))
continue;

@@ -845,7 +847,7 @@ fetch_task_cputime(struct task_struct *t,
if (t->vtime_snap_whence == VTIME_SYS)
*sdelta = delta;
}
- } while (read_seqretry(&t->vtime_seqlock, seq));
+ } while (read_seqcount_retry(&t->vtime_seqcount, seq));
}


@@ -853,6 +855,14 @@ void task_cputime(struct task_struct *t, cputime_t *utime, cputime_t *stime)
{
cputime_t udelta, sdelta;

+ if (!vtime_accounting_enabled()) {
+ if (utime)
+ *utime = t->utime;
+ if (stime)
+ *stime = t->stime;
+ return;
+ }
+
fetch_task_cputime(t, utime, stime, &t->utime,
&t->stime, &udelta, &sdelta);
if (utime)
@@ -866,6 +876,14 @@ void task_cputime_scaled(struct task_struct *t,
{
cputime_t udelta, sdelta;

+ if (!vtime_accounting_enabled()) {
+ if (utimescaled)
+ *utimescaled = t->utimescaled;
+ if (stimescaled)
+ *stimescaled = t->stimescaled;
+ return;
+ }
+
fetch_task_cputime(t, utimescaled, stimescaled,
&t->utimescaled, &t->stimescaled, &udelta, &sdelta);
if (utimescaled)
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 8b0a15e285f9..cd64c979d0e1 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -176,8 +176,10 @@ static void enqueue_pushable_dl_task(struct rq *rq, struct task_struct *p)
}
}

- if (leftmost)
+ if (leftmost) {
dl_rq->pushable_dl_tasks_leftmost = &p->pushable_dl_tasks;
+ dl_rq->earliest_dl.next = p->dl.deadline;
+ }

rb_link_node(&p->pushable_dl_tasks, parent, link);
rb_insert_color(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
@@ -195,6 +197,10 @@ static void dequeue_pushable_dl_task(struct rq *rq, struct task_struct *p)

next_node = rb_next(&p->pushable_dl_tasks);
dl_rq->pushable_dl_tasks_leftmost = next_node;
+ if (next_node) {
+ dl_rq->earliest_dl.next = rb_entry(next_node,
+ struct task_struct, pushable_dl_tasks)->dl.deadline;
+ }
}

rb_erase(&p->pushable_dl_tasks, &dl_rq->pushable_dl_tasks_root);
@@ -782,42 +788,14 @@ static void update_curr_dl(struct rq *rq)

#ifdef CONFIG_SMP

-static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu);
-
-static inline u64 next_deadline(struct rq *rq)
-{
- struct task_struct *next = pick_next_earliest_dl_task(rq, rq->cpu);
-
- if (next && dl_prio(next->prio))
- return next->dl.deadline;
- else
- return 0;
-}
-
static void inc_dl_deadline(struct dl_rq *dl_rq, u64 deadline)
{
struct rq *rq = rq_of_dl_rq(dl_rq);

if (dl_rq->earliest_dl.curr == 0 ||
dl_time_before(deadline, dl_rq->earliest_dl.curr)) {
- /*
- * If the dl_rq had no -deadline tasks, or if the new task
- * has shorter deadline than the current one on dl_rq, we
- * know that the previous earliest becomes our next earliest,
- * as the new task becomes the earliest itself.
- */
- dl_rq->earliest_dl.next = dl_rq->earliest_dl.curr;
dl_rq->earliest_dl.curr = deadline;
cpudl_set(&rq->rd->cpudl, rq->cpu, deadline, 1);
- } else if (dl_rq->earliest_dl.next == 0 ||
- dl_time_before(deadline, dl_rq->earliest_dl.next)) {
- /*
- * On the other hand, if the new -deadline task has a
- * a later deadline than the earliest one on dl_rq, but
- * it is earlier than the next (if any), we must
- * recompute the next-earliest.
- */
- dl_rq->earliest_dl.next = next_deadline(rq);
}
}

@@ -839,7 +817,6 @@ static void dec_dl_deadline(struct dl_rq *dl_rq, u64 deadline)

entry = rb_entry(leftmost, struct sched_dl_entity, rb_node);
dl_rq->earliest_dl.curr = entry->deadline;
- dl_rq->earliest_dl.next = next_deadline(rq);
cpudl_set(&rq->rd->cpudl, rq->cpu, entry->deadline, 1);
}
}
@@ -1274,28 +1251,6 @@ static int pick_dl_task(struct rq *rq, struct task_struct *p, int cpu)
return 0;
}

-/* Returns the second earliest -deadline task, NULL otherwise */
-static struct task_struct *pick_next_earliest_dl_task(struct rq *rq, int cpu)
-{
- struct rb_node *next_node = rq->dl.rb_leftmost;
- struct sched_dl_entity *dl_se;
- struct task_struct *p = NULL;
-
-next_node:
- next_node = rb_next(next_node);
- if (next_node) {
- dl_se = rb_entry(next_node, struct sched_dl_entity, rb_node);
- p = dl_task_of(dl_se);
-
- if (pick_dl_task(rq, p, cpu))
- return p;
-
- goto next_node;
- }
-
- return NULL;
-}
-
/*
* Return the earliest pushable rq's task, which is suitable to be executed
* on the CPU, NULL otherwise:
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index cfdc0e61066c..1926606ece80 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -738,12 +738,56 @@ static void update_curr_fair(struct rq *rq)
update_curr(cfs_rq_of(&rq->curr->se));
}

+#ifdef CONFIG_SCHEDSTATS
+static inline void
+update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ u64 wait_start = rq_clock(rq_of(cfs_rq));
+
+ if (entity_is_task(se) && task_on_rq_migrating(task_of(se)) &&
+ likely(wait_start > se->statistics.wait_start))
+ wait_start -= se->statistics.wait_start;
+
+ se->statistics.wait_start = wait_start;
+}
+
+static void
+update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+ struct task_struct *p;
+ u64 delta = rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start;
+
+ if (entity_is_task(se)) {
+ p = task_of(se);
+ if (task_on_rq_migrating(p)) {
+ /*
+ * Preserve migrating task's wait time so wait_start
+ * time stamp can be adjusted to accumulate wait time
+ * prior to migration.
+ */
+ se->statistics.wait_start = delta;
+ return;
+ }
+ trace_sched_stat_wait(p, delta);
+ }
+
+ se->statistics.wait_max = max(se->statistics.wait_max, delta);
+ se->statistics.wait_count++;
+ se->statistics.wait_sum += delta;
+ se->statistics.wait_start = 0;
+}
+#else
static inline void
update_stats_wait_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
- schedstat_set(se->statistics.wait_start, rq_clock(rq_of(cfs_rq)));
}

+static inline void
+update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
+{
+}
+#endif
+
/*
* Task is being enqueued - update stats:
*/
@@ -757,23 +801,6 @@ static void update_stats_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
update_stats_wait_start(cfs_rq, se);
}

-static void
-update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
-{
- schedstat_set(se->statistics.wait_max, max(se->statistics.wait_max,
- rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start));
- schedstat_set(se->statistics.wait_count, se->statistics.wait_count + 1);
- schedstat_set(se->statistics.wait_sum, se->statistics.wait_sum +
- rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
-#ifdef CONFIG_SCHEDSTATS
- if (entity_is_task(se)) {
- trace_sched_stat_wait(task_of(se),
- rq_clock(rq_of(cfs_rq)) - se->statistics.wait_start);
- }
-#endif
- schedstat_set(se->statistics.wait_start, 0);
-}
-
static inline void
update_stats_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
@@ -2155,6 +2182,7 @@ void task_numa_work(struct callback_head *work)
unsigned long migrate, next_scan, now = jiffies;
struct task_struct *p = current;
struct mm_struct *mm = p->mm;
+ u64 runtime = p->se.sum_exec_runtime;
struct vm_area_struct *vma;
unsigned long start, end;
unsigned long nr_pte_updates = 0;
@@ -2277,6 +2305,17 @@ void task_numa_work(struct callback_head *work)
else
reset_ptenuma_scan(p);
up_read(&mm->mmap_sem);
+
+ /*
+ * Make sure tasks use at least 32x as much time to run other code
+ * than they used here, to limit NUMA PTE scanning overhead to 3% max.
+ * Usually update_task_scan_period slows down scanning enough; on an
+ * overloaded system we need to limit overhead on a per task basis.
+ */
+ if (unlikely(p->se.sum_exec_runtime != runtime)) {
+ u64 diff = p->se.sum_exec_runtime - runtime;
+ p->node_stamp += 32 * diff;
+ }
}

/*
@@ -2670,12 +2709,64 @@ static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
{
long delta = cfs_rq->avg.load_avg - cfs_rq->tg_load_avg_contrib;

+ /*
+ * No need to update load_avg for root_task_group as it is not used.
+ */
+ if (cfs_rq->tg == &root_task_group)
+ return;
+
if (force || abs(delta) > cfs_rq->tg_load_avg_contrib / 64) {
atomic_long_add(delta, &cfs_rq->tg->load_avg);
cfs_rq->tg_load_avg_contrib = cfs_rq->avg.load_avg;
}
}

+/*
+ * Called within set_task_rq() right before setting a task's cpu. The
+ * caller only guarantees p->pi_lock is held; no other assumptions,
+ * including the state of rq->lock, should be made.
+ */
+void set_task_rq_fair(struct sched_entity *se,
+ struct cfs_rq *prev, struct cfs_rq *next)
+{
+ if (!sched_feat(ATTACH_AGE_LOAD))
+ return;
+
+ /*
+ * We are supposed to update the task to "current" time, then its up to
+ * date and ready to go to new CPU/cfs_rq. But we have difficulty in
+ * getting what current time is, so simply throw away the out-of-date
+ * time. This will result in the wakee task is less decayed, but giving
+ * the wakee more load sounds not bad.
+ */
+ if (se->avg.last_update_time && prev) {
+ u64 p_last_update_time;
+ u64 n_last_update_time;
+
+#ifndef CONFIG_64BIT
+ u64 p_last_update_time_copy;
+ u64 n_last_update_time_copy;
+
+ do {
+ p_last_update_time_copy = prev->load_last_update_time_copy;
+ n_last_update_time_copy = next->load_last_update_time_copy;
+
+ smp_rmb();
+
+ p_last_update_time = prev->avg.last_update_time;
+ n_last_update_time = next->avg.last_update_time;
+
+ } while (p_last_update_time != p_last_update_time_copy ||
+ n_last_update_time != n_last_update_time_copy);
+#else
+ p_last_update_time = prev->avg.last_update_time;
+ n_last_update_time = next->avg.last_update_time;
+#endif
+ __update_load_avg(p_last_update_time, cpu_of(rq_of(prev)),
+ &se->avg, 0, 0, NULL);
+ se->avg.last_update_time = n_last_update_time;
+ }
+}
#else /* CONFIG_FAIR_GROUP_SCHED */
static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force) {}
#endif /* CONFIG_FAIR_GROUP_SCHED */
@@ -2809,48 +2900,48 @@ dequeue_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
max_t(s64, cfs_rq->runnable_load_sum - se->avg.load_sum, 0);
}

-/*
- * Task first catches up with cfs_rq, and then subtract
- * itself from the cfs_rq (task must be off the queue now).
- */
-void remove_entity_load_avg(struct sched_entity *se)
-{
- struct cfs_rq *cfs_rq = cfs_rq_of(se);
- u64 last_update_time;
-
#ifndef CONFIG_64BIT
+static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
+{
u64 last_update_time_copy;
+ u64 last_update_time;

do {
last_update_time_copy = cfs_rq->load_last_update_time_copy;
smp_rmb();
last_update_time = cfs_rq->avg.last_update_time;
} while (last_update_time != last_update_time_copy);
-#else
- last_update_time = cfs_rq->avg.last_update_time;
-#endif

- __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
- atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
- atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
+ return last_update_time;
}
-
-/*
- * Update the rq's load with the elapsed running time before entering
- * idle. if the last scheduled task is not a CFS task, idle_enter will
- * be the only way to update the runnable statistic.
- */
-void idle_enter_fair(struct rq *this_rq)
+#else
+static inline u64 cfs_rq_last_update_time(struct cfs_rq *cfs_rq)
{
+ return cfs_rq->avg.last_update_time;
}
+#endif

/*
- * Update the rq's load with the elapsed idle time before a task is
- * scheduled. if the newly scheduled task is not a CFS task, idle_exit will
- * be the only way to update the runnable statistic.
+ * Task first catches up with cfs_rq, and then subtract
+ * itself from the cfs_rq (task must be off the queue now).
*/
-void idle_exit_fair(struct rq *this_rq)
+void remove_entity_load_avg(struct sched_entity *se)
{
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ u64 last_update_time;
+
+ /*
+ * Newly created task or never used group entity should not be removed
+ * from its (source) cfs_rq
+ */
+ if (se->avg.last_update_time == 0)
+ return;
+
+ last_update_time = cfs_rq_last_update_time(cfs_rq);
+
+ __update_load_avg(last_update_time, cpu_of(rq_of(cfs_rq)), &se->avg, 0, 0, NULL);
+ atomic_long_add(se->avg.load_avg, &cfs_rq->removed_load_avg);
+ atomic_long_add(se->avg.util_avg, &cfs_rq->removed_util_avg);
}

static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq)
@@ -4240,42 +4331,37 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
*/

/*
- * 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
+ * The exact cpuload calculated at every tick would be:
+ *
+ * load' = (1 - 1/2^i) * load + (1/2^i) * 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
+ * If a cpu misses updates for n ticks (as it was idle) and update gets
+ * called on the n+1-th tick when cpu may be busy, then we have:
+ *
+ * load_n = (1 - 1/2^i)^n * load_0
+ * load_n+1 = (1 - 1/2^i) * load_n + (1/2^i) * 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
+ *
+ * load' = (1 - 1/2^i)^n * load
+ *
+ * Because x^(n+m) := x^n * x^m we can decompose any x^n in power-of-2 factors.
+ * This allows us to precompute the above in said factors, thereby allowing the
+ * reduction of an arbitrary n in O(log_2 n) steps. (See also
+ * fixed_power_int())
*
* 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} };
+
+static const u8 degrade_zero_ticks[CPU_LOAD_IDX_MAX] = {0, 8, 32, 64, 128};
+static const u8 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, 0 },
+ { 112, 98, 75, 43, 15, 1, 0, 0 },
+ { 120, 112, 98, 76, 45, 16, 2, 0 }
+};

/*
* Update cpu_load for any missed ticks, due to tickless idle. The backlog
@@ -4306,14 +4392,46 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
return load;
}

-/*
+/**
+ * __update_cpu_load - update the rq->cpu_load[] statistics
+ * @this_rq: The rq to update statistics for
+ * @this_load: The current load
+ * @pending_updates: The number of missed updates
+ * @active: !0 for NOHZ_FULL
+ *
* Update rq->cpu_load[] statistics. This function is usually called every
- * scheduler tick (TICK_NSEC). With tickless idle this will not be called
- * every tick. We fix it up based on jiffies.
+ * scheduler tick (TICK_NSEC).
+ *
+ * This function computes a decaying average:
+ *
+ * load[i]' = (1 - 1/2^i) * load[i] + (1/2^i) * load
+ *
+ * Because of NOHZ it might not get called on every tick which gives need for
+ * the @pending_updates argument.
+ *
+ * load[i]_n = (1 - 1/2^i) * load[i]_n-1 + (1/2^i) * load_n-1
+ * = A * load[i]_n-1 + B ; A := (1 - 1/2^i), B := (1/2^i) * load
+ * = A * (A * load[i]_n-2 + B) + B
+ * = A * (A * (A * load[i]_n-3 + B) + B) + B
+ * = A^3 * load[i]_n-3 + (A^2 + A + 1) * B
+ * = A^n * load[i]_0 + (A^(n-1) + A^(n-2) + ... + 1) * B
+ * = A^n * load[i]_0 + ((1 - A^n) / (1 - A)) * B
+ * = (1 - 1/2^i)^n * (load[i]_0 - load) + load
+ *
+ * In the above we've assumed load_n := load, which is true for NOHZ_FULL as
+ * any change in load would have resulted in the tick being turned back on.
+ *
+ * For regular NOHZ, this reduces to:
+ *
+ * load[i]_n = (1 - 1/2^i)^n * load[i]_0
+ *
+ * see decay_load_misses(). For NOHZ_FULL we get to subtract and add the extra
+ * term. See the @active paramter.
*/
static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
- unsigned long pending_updates)
+ unsigned long pending_updates, int active)
{
+ unsigned long tickless_load = active ? this_rq->cpu_load[0] : 0;
int i, scale;

this_rq->nr_load_updates++;
@@ -4325,8 +4443,9 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,

/* scale is effectively 1 << i now, and >> i divides by scale */

- old_load = this_rq->cpu_load[i];
+ old_load = this_rq->cpu_load[i] - tickless_load;
old_load = decay_load_missed(old_load, pending_updates - 1, i);
+ old_load += tickless_load;
new_load = this_load;
/*
* Round up the averaging division if load is increasing. This
@@ -4381,16 +4500,17 @@ static void update_idle_cpu_load(struct rq *this_rq)
pending_updates = curr_jiffies - this_rq->last_load_update_tick;
this_rq->last_load_update_tick = curr_jiffies;

- __update_cpu_load(this_rq, load, pending_updates);
+ __update_cpu_load(this_rq, load, pending_updates, 0);
}

/*
* Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
*/
-void update_cpu_load_nohz(void)
+void update_cpu_load_nohz(int active)
{
struct rq *this_rq = this_rq();
unsigned long curr_jiffies = READ_ONCE(jiffies);
+ unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
unsigned long pending_updates;

if (curr_jiffies == this_rq->last_load_update_tick)
@@ -4401,10 +4521,11 @@ void update_cpu_load_nohz(void)
if (pending_updates) {
this_rq->last_load_update_tick = curr_jiffies;
/*
- * We were idle, this means load 0, the current load might be
- * !0 due to remote wakeups and the sort.
+ * In the regular NOHZ case, we were idle, this means load 0.
+ * In the NOHZ_FULL case, we were non-idle, we should consider
+ * its weighted load.
*/
- __update_cpu_load(this_rq, 0, pending_updates);
+ __update_cpu_load(this_rq, load, pending_updates, active);
}
raw_spin_unlock(&this_rq->lock);
}
@@ -4420,7 +4541,7 @@ void update_cpu_load_active(struct rq *this_rq)
* See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
*/
this_rq->last_load_update_tick = jiffies;
- __update_cpu_load(this_rq, load, 1);
+ __update_cpu_load(this_rq, load, 1, 1);
}

/*
@@ -5007,8 +5128,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
/*
* Called immediately before a task is migrated to a new cpu; task_cpu(p) and
* cfs_rq_of(p) references at time of call are still valid and identify the
- * previous cpu. However, the caller only guarantees p->pi_lock is held; no
- * other assumptions, including the state of rq->lock, should be made.
+ * previous cpu. The caller guarantees p->pi_lock or task_rq(p)->lock is held.
*/
static void migrate_task_rq_fair(struct task_struct *p)
{
@@ -5721,8 +5841,8 @@ static void detach_task(struct task_struct *p, struct lb_env *env)
{
lockdep_assert_held(&env->src_rq->lock);

- deactivate_task(env->src_rq, p, 0);
p->on_rq = TASK_ON_RQ_MIGRATING;
+ deactivate_task(env->src_rq, p, 0);
set_task_cpu(p, env->dst_cpu);
}

@@ -5855,8 +5975,8 @@ static void attach_task(struct rq *rq, struct task_struct *p)
lockdep_assert_held(&rq->lock);

BUG_ON(task_rq(p) != rq);
- p->on_rq = TASK_ON_RQ_QUEUED;
activate_task(rq, p, 0);
+ p->on_rq = TASK_ON_RQ_QUEUED;
check_preempt_curr(rq, p, 0);
}

@@ -6302,7 +6422,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
bool *overload)
{
unsigned long load;
- int i;
+ int i, nr_running;

memset(sgs, 0, sizeof(*sgs));

@@ -6319,7 +6439,8 @@ static inline void update_sg_lb_stats(struct lb_env *env,
sgs->group_util += cpu_util(i);
sgs->sum_nr_running += rq->cfs.h_nr_running;

- if (rq->nr_running > 1)
+ nr_running = rq->nr_running;
+ if (nr_running > 1)
*overload = true;

#ifdef CONFIG_NUMA_BALANCING
@@ -6327,7 +6448,10 @@ static inline void update_sg_lb_stats(struct lb_env *env,
sgs->nr_preferred_running += rq->nr_preferred_running;
#endif
sgs->sum_weighted_load += weighted_cpuload(i);
- if (idle_cpu(i))
+ /*
+ * No need to call idle_cpu() if nr_running is not 0
+ */
+ if (!nr_running && idle_cpu(i))
sgs->idle_cpus++;
}

@@ -7248,8 +7372,6 @@ static int idle_balance(struct rq *this_rq)
int pulled_task = 0;
u64 curr_cost = 0;

- idle_enter_fair(this_rq);
-
/*
* We must set idle_stamp _before_ calling idle_balance(), such that we
* measure the duration of idle_balance() as idle time.
@@ -7330,10 +7452,8 @@ static int idle_balance(struct rq *this_rq)
if (this_rq->nr_running != this_rq->cfs.h_nr_running)
pulled_task = -1;

- if (pulled_task) {
- idle_exit_fair(this_rq);
+ if (pulled_task)
this_rq->idle_stamp = 0;
- }

return pulled_task;
}
diff --git a/kernel/sched/idle_task.c b/kernel/sched/idle_task.c
index c4ae0f1fdf9b..47ce94931f1b 100644
--- a/kernel/sched/idle_task.c
+++ b/kernel/sched/idle_task.c
@@ -47,7 +47,6 @@ dequeue_task_idle(struct rq *rq, struct task_struct *p, int flags)

static void put_prev_task_idle(struct rq *rq, struct task_struct *prev)
{
- idle_exit_fair(rq);
rq_last_tick_reset(rq);
}

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index b242775bf670..a5a6b3e60868 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -248,7 +248,12 @@ struct task_group {
unsigned long shares;

#ifdef CONFIG_SMP
- atomic_long_t load_avg;
+ /*
+ * load_avg can be heavily contended at clock tick time, so put
+ * it in its own cacheline separated from the fields above which
+ * will also be accessed at each tick.
+ */
+ atomic_long_t load_avg ____cacheline_aligned;
#endif
#endif

@@ -335,7 +340,15 @@ extern void sched_move_task(struct task_struct *tsk);

#ifdef CONFIG_FAIR_GROUP_SCHED
extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);
-#endif
+
+#ifdef CONFIG_SMP
+extern void set_task_rq_fair(struct sched_entity *se,
+ struct cfs_rq *prev, struct cfs_rq *next);
+#else /* !CONFIG_SMP */
+static inline void set_task_rq_fair(struct sched_entity *se,
+ struct cfs_rq *prev, struct cfs_rq *next) { }
+#endif /* CONFIG_SMP */
+#endif /* CONFIG_FAIR_GROUP_SCHED */

#else /* CONFIG_CGROUP_SCHED */

@@ -933,6 +946,7 @@ static inline void set_task_rq(struct task_struct *p, unsigned int cpu)
#endif

#ifdef CONFIG_FAIR_GROUP_SCHED
+ set_task_rq_fair(&p->se, p->se.cfs_rq, tg->cfs_rq[cpu]);
p->se.cfs_rq = tg->cfs_rq[cpu];
p->se.parent = tg->se[cpu];
#endif
@@ -1113,46 +1127,8 @@ static inline void finish_lock_switch(struct rq *rq, struct task_struct *prev)
#define WEIGHT_IDLEPRIO 3
#define WMULT_IDLEPRIO 1431655765

-/*
- * Nice levels are multiplicative, with a gentle 10% change for every
- * nice level changed. I.e. when a CPU-bound task goes from nice 0 to
- * nice 1, it will get ~10% less CPU time than another CPU-bound task
- * that remained on nice 0.
- *
- * The "10% effect" is relative and cumulative: from _any_ nice level,
- * if you go up 1 level, it's -10% CPU usage, if you go down 1 level
- * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25.
- * If a task goes up by ~10% and another task goes down by ~10% then
- * the relative distance between them is ~25%.)
- */
-static const int prio_to_weight[40] = {
- /* -20 */ 88761, 71755, 56483, 46273, 36291,
- /* -15 */ 29154, 23254, 18705, 14949, 11916,
- /* -10 */ 9548, 7620, 6100, 4904, 3906,
- /* -5 */ 3121, 2501, 1991, 1586, 1277,
- /* 0 */ 1024, 820, 655, 526, 423,
- /* 5 */ 335, 272, 215, 172, 137,
- /* 10 */ 110, 87, 70, 56, 45,
- /* 15 */ 36, 29, 23, 18, 15,
-};
-
-/*
- * Inverse (2^32/x) values of the prio_to_weight[] array, precalculated.
- *
- * In cases where the weight does not change often, we can use the
- * precalculated inverse to speed up arithmetics by turning divisions
- * into multiplications:
- */
-static const u32 prio_to_wmult[40] = {
- /* -20 */ 48388, 59856, 76040, 92818, 118348,
- /* -15 */ 147320, 184698, 229616, 287308, 360437,
- /* -10 */ 449829, 563644, 704093, 875809, 1099582,
- /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326,
- /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587,
- /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126,
- /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717,
- /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153,
-};
+extern const int sched_prio_to_weight[40];
+extern const u32 sched_prio_to_wmult[40];

#define ENQUEUE_WAKEUP 0x01
#define ENQUEUE_HEAD 0x02
@@ -1252,16 +1228,8 @@ extern void update_group_capacity(struct sched_domain *sd, int cpu);

extern void trigger_load_balance(struct rq *rq);

-extern void idle_enter_fair(struct rq *this_rq);
-extern void idle_exit_fair(struct rq *this_rq);
-
extern void set_cpus_allowed_common(struct task_struct *p, const struct cpumask *new_mask);

-#else
-
-static inline void idle_enter_fair(struct rq *rq) { }
-static inline void idle_exit_fair(struct rq *rq) { }
-
#endif

#ifdef CONFIG_CPU_IDLE
diff --git a/kernel/stop_machine.c b/kernel/stop_machine.c
index a3bbaee77c58..edb6de4f5908 100644
--- a/kernel/stop_machine.c
+++ b/kernel/stop_machine.c
@@ -28,7 +28,6 @@
*/
struct cpu_stop_done {
atomic_t nr_todo; /* nr left to execute */
- bool executed; /* actually executed? */
int ret; /* collected return value */
struct completion completion; /* fired if nr_todo reaches 0 */
};
@@ -63,14 +62,10 @@ static void cpu_stop_init_done(struct cpu_stop_done *done, unsigned int nr_todo)
}

/* signal completion unless @done is NULL */
-static void cpu_stop_signal_done(struct cpu_stop_done *done, bool executed)
+static void cpu_stop_signal_done(struct cpu_stop_done *done)
{
- if (done) {
- if (executed)
- done->executed = true;
- if (atomic_dec_and_test(&done->nr_todo))
- complete(&done->completion);
- }
+ if (atomic_dec_and_test(&done->nr_todo))
+ complete(&done->completion);
}

static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
@@ -81,17 +76,21 @@ static void __cpu_stop_queue_work(struct cpu_stopper *stopper,
}

/* queue @work to @stopper. if offline, @work is completed immediately */
-static void cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
+static bool cpu_stop_queue_work(unsigned int cpu, struct cpu_stop_work *work)
{
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
unsigned long flags;
+ bool enabled;

spin_lock_irqsave(&stopper->lock, flags);
- if (stopper->enabled)
+ enabled = stopper->enabled;
+ if (enabled)
__cpu_stop_queue_work(stopper, work);
- else
- cpu_stop_signal_done(work->done, false);
+ else if (work->done)
+ cpu_stop_signal_done(work->done);
spin_unlock_irqrestore(&stopper->lock, flags);
+
+ return enabled;
}

/**
@@ -124,9 +123,10 @@ int stop_one_cpu(unsigned int cpu, cpu_stop_fn_t fn, void *arg)
struct cpu_stop_work work = { .fn = fn, .arg = arg, .done = &done };

cpu_stop_init_done(&done, 1);
- cpu_stop_queue_work(cpu, &work);
+ if (!cpu_stop_queue_work(cpu, &work))
+ return -ENOENT;
wait_for_completion(&done.completion);
- return done.executed ? done.ret : -ENOENT;
+ return done.ret;
}

/* This controls the threads on each CPU. */
@@ -258,7 +258,6 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
struct cpu_stop_work work1, work2;
struct multi_stop_data msdata;

- preempt_disable();
msdata = (struct multi_stop_data){
.fn = fn,
.data = arg,
@@ -277,16 +276,11 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *

if (cpu1 > cpu2)
swap(cpu1, cpu2);
- if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2)) {
- preempt_enable();
+ if (cpu_stop_queue_two_works(cpu1, &work1, cpu2, &work2))
return -ENOENT;
- }
-
- preempt_enable();

wait_for_completion(&done.completion);
-
- return done.executed ? done.ret : -ENOENT;
+ return done.ret;
}

/**
@@ -302,23 +296,28 @@ int stop_two_cpus(unsigned int cpu1, unsigned int cpu2, cpu_stop_fn_t fn, void *
*
* CONTEXT:
* Don't care.
+ *
+ * RETURNS:
+ * true if cpu_stop_work was queued successfully and @fn will be called,
+ * false otherwise.
*/
-void stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
+bool stop_one_cpu_nowait(unsigned int cpu, cpu_stop_fn_t fn, void *arg,
struct cpu_stop_work *work_buf)
{
*work_buf = (struct cpu_stop_work){ .fn = fn, .arg = arg, };
- cpu_stop_queue_work(cpu, work_buf);
+ return cpu_stop_queue_work(cpu, work_buf);
}

/* static data for stop_cpus */
static DEFINE_MUTEX(stop_cpus_mutex);

-static void queue_stop_cpus_work(const struct cpumask *cpumask,
+static bool queue_stop_cpus_work(const struct cpumask *cpumask,
cpu_stop_fn_t fn, void *arg,
struct cpu_stop_done *done)
{
struct cpu_stop_work *work;
unsigned int cpu;
+ bool queued = false;

/*
* Disable preemption while queueing to avoid getting
@@ -331,9 +330,12 @@ static void queue_stop_cpus_work(const struct cpumask *cpumask,
work->fn = fn;
work->arg = arg;
work->done = done;
- cpu_stop_queue_work(cpu, work);
+ if (cpu_stop_queue_work(cpu, work))
+ queued = true;
}
lg_global_unlock(&stop_cpus_lock);
+
+ return queued;
}

static int __stop_cpus(const struct cpumask *cpumask,
@@ -342,9 +344,10 @@ static int __stop_cpus(const struct cpumask *cpumask,
struct cpu_stop_done done;

cpu_stop_init_done(&done, cpumask_weight(cpumask));
- queue_stop_cpus_work(cpumask, fn, arg, &done);
+ if (!queue_stop_cpus_work(cpumask, fn, arg, &done))
+ return -ENOENT;
wait_for_completion(&done.completion);
- return done.executed ? done.ret : -ENOENT;
+ return done.ret;
}

/**
@@ -432,7 +435,6 @@ static void cpu_stopper_thread(unsigned int cpu)
{
struct cpu_stopper *stopper = &per_cpu(cpu_stopper, cpu);
struct cpu_stop_work *work;
- int ret;

repeat:
work = NULL;
@@ -448,23 +450,19 @@ static void cpu_stopper_thread(unsigned int cpu)
cpu_stop_fn_t fn = work->fn;
void *arg = work->arg;
struct cpu_stop_done *done = work->done;
- char ksym_buf[KSYM_NAME_LEN] __maybe_unused;
-
- /* cpu stop callbacks are not allowed to sleep */
- preempt_disable();
+ int ret;

+ /* cpu stop callbacks must not sleep, make in_atomic() == T */
+ preempt_count_inc();
ret = fn(arg);
- if (ret)
- done->ret = ret;
-
- /* restore preemption and check it's still balanced */
- preempt_enable();
+ if (done) {
+ if (ret)
+ done->ret = ret;
+ cpu_stop_signal_done(done);
+ }
+ preempt_count_dec();
WARN_ONCE(preempt_count(),
- "cpu_stop: %s(%p) leaked preempt count\n",
- kallsyms_lookup((unsigned long)fn, NULL, NULL, NULL,
- ksym_buf), arg);
-
- cpu_stop_signal_done(done, true);
+ "cpu_stop: %pf(%p) leaked preempt count\n", fn, arg);
goto repeat;
}
}
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 7c7ec4515983..11ce59916c1a 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -694,11 +694,11 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts,
return tick;
}

-static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
+static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now, int active)
{
/* Update jiffies first */
tick_do_update_jiffies64(now);
- update_cpu_load_nohz();
+ update_cpu_load_nohz(active);

calc_load_exit_idle();
touch_softlockup_watchdog();
@@ -725,7 +725,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts)
if (can_stop_full_tick())
tick_nohz_stop_sched_tick(ts, ktime_get(), cpu);
else if (ts->tick_stopped)
- tick_nohz_restart_sched_tick(ts, ktime_get());
+ tick_nohz_restart_sched_tick(ts, ktime_get(), 1);
#endif
}

@@ -875,7 +875,7 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
unsigned long ticks;

- if (vtime_accounting_enabled())
+ if (vtime_accounting_cpu_enabled())
return;
/*
* We stopped the tick in idle. Update process times would miss the
@@ -916,7 +916,7 @@ void tick_nohz_idle_exit(void)
tick_nohz_stop_idle(ts, now);

if (ts->tick_stopped) {
- tick_nohz_restart_sched_tick(ts, now);
+ tick_nohz_restart_sched_tick(ts, now, 0);
tick_nohz_account_idle_ticks(ts);
}

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