[git pull] scheduler fixes

Ingo Molnar
2008-03-04T17:08:09Z

Linus, please pull the latest scheduler fixes git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/mingo/linux-2.6-sched-devel.git for-linus

Thanks,

Ingo

------------------>
Peter Zijlstra (1):
sched: revert load_balance_monitor() changes

include/linux/sched.h | 4 -
kernel/sched.c | 283 ++++++-------------------------------------------
kernel/sched_fair.c | 115 ++++++--------------
kernel/sched_rt.c | 4 -
kernel/sysctl.c | 18 ---
5 files changed, 70 insertions(+), 354 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 2c9621f..9ae4030 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1542,10 +1542,6 @@ extern unsigned int sysctl_sched_child_runs_first;
extern unsigned int sysctl_sched_features;
extern unsigned int sysctl_sched_migration_cost;
extern unsigned int sysctl_sched_nr_migrate;
-#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
-extern unsigned int sysctl_sched_min_bal_int_shares;
-extern unsigned int sysctl_sched_max_bal_int_shares;
-#endif

int sched_nr_latency_handler(struct ctl_table *table, int write,
struct file *file, void __user *buffer, size_t *length,
diff --git a/kernel/sched.c b/kernel/sched.c
index f06950c..dcd553c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -174,41 +174,6 @@ struct task_group {
struct sched_entity **se;
/* runqueue "owned" by this group on each cpu */
struct cfs_rq **cfs_rq;
-
- /*
- * shares assigned to a task group governs how much of cpu bandwidth
- * is allocated to the group. The more shares a group has, the more is
- * the cpu bandwidth allocated to it.
- *
- * For ex, lets say that there are three task groups, A, B and C which
- * have been assigned shares 1000, 2000 and 3000 respectively. Then,
- * cpu bandwidth allocated by the scheduler to task groups A, B and C
- * should be:
- *
- * Bw(A) = 1000/(1000+2000+3000) * 100 = 16.66%
- * Bw(B) = 2000/(1000+2000+3000) * 100 = 33.33%
- * Bw(C) = 3000/(1000+2000+3000) * 100 = 50%
- *
- * The weight assigned to a task group's schedulable entities on every
- * cpu (task_group.se[a_cpu]->load.weight) is derived from the task
- * group's shares. For ex: lets say that task group A has been
- * assigned shares of 1000 and there are two CPUs in a system. Then,
- *
- * tg_A->se[0]->load.weight = tg_A->se[1]->load.weight = 1000;
- *
- * Note: It's not necessary that each of a task's group schedulable
- * entity have the same weight on all CPUs. If the group
- * has 2 of its tasks on CPU0 and 1 task on CPU1, then a
- * better distribution of weight could be:
- *
- * tg_A->se[0]->load.weight = 2/3 * 2000 = 1333
- * tg_A->se[1]->load.weight = 1/2 * 2000 = 667
- *
- * rebalance_shares() is responsible for distributing the shares of a
- * task groups like this among the group's schedulable entities across
- * cpus.
- *
- */
unsigned long shares;
#endif

@@ -250,22 +215,12 @@ static DEFINE_SPINLOCK(task_group_lock);
static DEFINE_MUTEX(doms_cur_mutex);

#ifdef CONFIG_FAIR_GROUP_SCHED
-#ifdef CONFIG_SMP
-/* kernel thread that runs rebalance_shares() periodically */
-static struct task_struct *lb_monitor_task;
-static int load_balance_monitor(void *unused);
-#endif
-
-static void set_se_shares(struct sched_entity *se, unsigned long shares);
-
#ifdef CONFIG_USER_SCHED
# define INIT_TASK_GROUP_LOAD (2*NICE_0_LOAD)
#else
# define INIT_TASK_GROUP_LOAD NICE_0_LOAD
#endif

-#define MIN_GROUP_SHARES 2
-
static int init_task_group_load = INIT_TASK_GROUP_LOAD;
#endif

@@ -1245,16 +1200,6 @@ static void cpuacct_charge(struct task_struct *tsk, u64 cputime);
static inline void cpuacct_charge(struct task_struct *tsk, u64 cputime) {}
#endif

-static inline void inc_cpu_load(struct rq *rq, unsigned long load)
-{
- update_load_add(&rq->load, load);
-}
-
-static inline void dec_cpu_load(struct rq *rq, unsigned long load)
-{
- update_load_sub(&rq->load, load);
-}
-
#ifdef CONFIG_SMP
static unsigned long source_load(int cpu, int type);
static unsigned long target_load(int cpu, int type);
@@ -1272,14 +1217,26 @@ static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);

#define sched_class_highest (&rt_sched_class)

-static void inc_nr_running(struct rq *rq)
+static inline void inc_load(struct rq *rq, const struct task_struct *p)
+{
+ update_load_add(&rq->load, p->se.load.weight);
+}
+
+static inline void dec_load(struct rq *rq, const struct task_struct *p)
+{
+ update_load_sub(&rq->load, p->se.load.weight);
+}
+
+static void inc_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running++;
+ inc_load(rq, p);
}

-static void dec_nr_running(struct rq *rq)
+static void dec_nr_running(struct task_struct *p, struct rq *rq)
{
rq->nr_running--;
+ dec_load(rq, p);
}

static void set_load_weight(struct task_struct *p)
@@ -1371,7 +1328,7 @@ static void activate_task(struct rq *rq, struct task_struct *p, int wakeup)
rq->nr_uninterruptible--;

enqueue_task(rq, p, wakeup);
- inc_nr_running(rq);
+ inc_nr_running(p, rq);
}

/*
@@ -1383,7 +1340,7 @@ static void deactivate_task(struct rq *rq, struct task_struct *p, int sleep)
rq->nr_uninterruptible++;

dequeue_task(rq, p, sleep);
- dec_nr_running(rq);
+ dec_nr_running(p, rq);
}

/**
@@ -2023,7 +1980,7 @@ void wake_up_new_task(struct task_struct *p, unsigned long clone_flags)
* management (if any):
*/
p->sched_class->task_new(rq, p);
- inc_nr_running(rq);
+ inc_nr_running(p, rq);
}
check_preempt_curr(rq, p);
#ifdef CONFIG_SMP
@@ -4362,8 +4319,10 @@ void set_user_nice(struct task_struct *p, long nice)
goto out_unlock;
}
on_rq = p->se.on_rq;
- if (on_rq)
+ if (on_rq) {
dequeue_task(rq, p, 0);
+ dec_load(rq, p);
+ }

p->static_prio = NICE_TO_PRIO(nice);
set_load_weight(p);
@@ -4373,6 +4332,7 @@ void set_user_nice(struct task_struct *p, long nice)

if (on_rq) {
enqueue_task(rq, p, 0);
+ inc_load(rq, p);
/*
* If the task increased its priority or is running and
* lowered its priority, then reschedule its CPU:
@@ -7087,21 +7047,6 @@ void __init sched_init_smp(void)
if (set_cpus_allowed(current, non_isolated_cpus) < 0)
BUG();
sched_init_granularity();
-
-#ifdef CONFIG_FAIR_GROUP_SCHED
- if (nr_cpu_ids == 1)
- return;
-
- lb_monitor_task = kthread_create(load_balance_monitor, NULL,
- "group_balance");
- if (!IS_ERR(lb_monitor_task)) {
- lb_monitor_task->flags |= PF_NOFREEZE;
- wake_up_process(lb_monitor_task);
- } else {
- printk(KERN_ERR "Could not create load balance monitor thread"
- "(error = %ld) \n", PTR_ERR(lb_monitor_task));
- }
-#endif
}
#else
void __init sched_init_smp(void)
@@ -7424,157 +7369,6 @@ void set_curr_task(int cpu, struct task_struct *p)

#ifdef CONFIG_GROUP_SCHED

-#if defined CONFIG_FAIR_GROUP_SCHED && defined CONFIG_SMP
-/*
- * distribute shares of all task groups among their schedulable entities,
- * to reflect load distribution across cpus.
- */
-static int rebalance_shares(struct sched_domain *sd, int this_cpu)
-{
- struct cfs_rq *cfs_rq;
- struct rq *rq = cpu_rq(this_cpu);
- cpumask_t sdspan = sd->span;
- int balanced = 1;
-
- /* Walk thr' all the task groups that we have */
- for_each_leaf_cfs_rq(rq, cfs_rq) {
- int i;
- unsigned long total_load = 0, total_shares;
- struct task_group *tg = cfs_rq->tg;
-
- /* Gather total task load of this group across cpus */
- for_each_cpu_mask(i, sdspan)
- total_load += tg->cfs_rq[i]->load.weight;
-
- /* Nothing to do if this group has no load */
- if (!total_load)
- continue;
-
- /*
- * tg->shares represents the number of cpu shares the task group
- * is eligible to hold on a single cpu. On N cpus, it is
- * eligible to hold (N * tg->shares) number of cpu shares.
- */
- total_shares = tg->shares * cpus_weight(sdspan);
-
- /*
- * redistribute total_shares across cpus as per the task load
- * distribution.
- */
- for_each_cpu_mask(i, sdspan) {
- unsigned long local_load, local_shares;
-
- local_load = tg->cfs_rq[i]->load.weight;
- local_shares = (local_load * total_shares) / total_load;
- if (!local_shares)
- local_shares = MIN_GROUP_SHARES;
- if (local_shares == tg->se[i]->load.weight)
- continue;
-
- spin_lock_irq(&cpu_rq(i)->lock);
- set_se_shares(tg->se[i], local_shares);
- spin_unlock_irq(&cpu_rq(i)->lock);
- balanced = 0;
- }
- }
-
- return balanced;
-}
-
-/*
- * How frequently should we rebalance_shares() across cpus?
- *
- * The more frequently we rebalance shares, the more accurate is the fairness
- * of cpu bandwidth distribution between task groups. However higher frequency
- * also implies increased scheduling overhead.
- *
- * sysctl_sched_min_bal_int_shares represents the minimum interval between
- * consecutive calls to rebalance_shares() in the same sched domain.
- *
- * sysctl_sched_max_bal_int_shares represents the maximum interval between
- * consecutive calls to rebalance_shares() in the same sched domain.
- *
- * These settings allows for the appropriate trade-off between accuracy of
- * fairness and the associated overhead.
- *
- */
-
-/* default: 8ms, units: milliseconds */
-const_debug unsigned int sysctl_sched_min_bal_int_shares = 8;
-
-/* default: 128ms, units: milliseconds */
-const_debug unsigned int sysctl_sched_max_bal_int_shares = 128;
-
-/* kernel thread that runs rebalance_shares() periodically */
-static int load_balance_monitor(void *unused)
-{
- unsigned int timeout = sysctl_sched_min_bal_int_shares;
- struct sched_param schedparm;
- int ret;
-
- /*
- * We don't want this thread's execution to be limited by the shares
- * assigned to default group (init_task_group). Hence make it run
- * as a SCHED_RR RT task at the lowest priority.
- */
- schedparm.sched_priority = 1;
- ret = sched_setscheduler(current, SCHED_RR, &schedparm);
- if (ret)
- printk(KERN_ERR "Couldn't set SCHED_RR policy for load balance"
- " monitor thread (error = %d) \n", ret);
-
- while (!kthread_should_stop()) {
- int i, cpu, balanced = 1;
-
- /* Prevent cpus going down or coming up */
- get_online_cpus();
- /* lockout changes to doms_cur[] array */
- lock_doms_cur();
- /*
- * Enter a rcu read-side critical section to safely walk rq->sd
- * chain on various cpus and to walk task group list
- * (rq->leaf_cfs_rq_list) in rebalance_shares().
- */
- rcu_read_lock();
-
- for (i = 0; i < ndoms_cur; i++) {
- cpumask_t cpumap = doms_cur[i];
- struct sched_domain *sd = NULL, *sd_prev = NULL;
-
- cpu = first_cpu(cpumap);
-
- /* Find the highest domain at which to balance shares */
- for_each_domain(cpu, sd) {
- if (!(sd->flags & SD_LOAD_BALANCE))
- continue;
- sd_prev = sd;
- }
-
- sd = sd_prev;
- /* sd == NULL? No load balance reqd in this domain */
- if (!sd)
- continue;
-
- balanced &= rebalance_shares(sd, cpu);
- }
-
- rcu_read_unlock();
-
- unlock_doms_cur();
- put_online_cpus();
-
- if (!balanced)
- timeout = sysctl_sched_min_bal_int_shares;
- else if (timeout < sysctl_sched_max_bal_int_shares)
- timeout *= 2;
-
- msleep_interruptible(timeout);
- }
-
- return 0;
-}
-#endif /* CONFIG_SMP */
-
#ifdef CONFIG_FAIR_GROUP_SCHED
static void free_fair_sched_group(struct task_group *tg)
{
@@ -7841,29 +7635,25 @@ void sched_move_task(struct task_struct *tsk)
}

#ifdef CONFIG_FAIR_GROUP_SCHED
-/* rq->lock to be locked by caller */
static void set_se_shares(struct sched_entity *se, unsigned long shares)
{
struct cfs_rq *cfs_rq = se->cfs_rq;
struct rq *rq = cfs_rq->rq;
int on_rq;

- if (!shares)
- shares = MIN_GROUP_SHARES;
+ spin_lock_irq(&rq->lock);

on_rq = se->on_rq;
- if (on_rq) {
+ if (on_rq)
dequeue_entity(cfs_rq, se, 0);
- dec_cpu_load(rq, se->load.weight);
- }

se->load.weight = shares;
se->load.inv_weight = div64_64((1ULL<<32), shares);

- if (on_rq) {
+ if (on_rq)
enqueue_entity(cfs_rq, se, 0);
- inc_cpu_load(rq, se->load.weight);
- }
+
+ spin_unlock_irq(&rq->lock);
}

static DEFINE_MUTEX(shares_mutex);
@@ -7873,18 +7663,18 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
int i;
unsigned long flags;

+ /*
+ * A weight of 0 or 1 can cause arithmetics problems.
+ * (The default weight is 1024 - so there's no practical
+ * limitation from this.)
+ */
+ if (shares < 2)
+ shares = 2;
+
mutex_lock(&shares_mutex);
if (tg->shares == shares)
goto done;

- if (shares < MIN_GROUP_SHARES)
- shares = MIN_GROUP_SHARES;
-
- /*
- * Prevent any load balance activity (rebalance_shares,
- * load_balance_fair) from referring to this group first,
- * by taking it off the rq->leaf_cfs_rq_list on each cpu.
- */
spin_lock_irqsave(&task_group_lock, flags);
for_each_possible_cpu(i)
unregister_fair_sched_group(tg, i);
@@ -7898,11 +7688,8 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
* w/o tripping rebalance_share or load_balance_fair.
*/
tg->shares = shares;
- for_each_possible_cpu(i) {
- spin_lock_irq(&cpu_rq(i)->lock);
+ for_each_possible_cpu(i)
set_se_shares(tg->se[i], shares);
- spin_unlock_irq(&cpu_rq(i)->lock);
- }

/*
* Enable load balance activity on this group, by inserting it back on
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index c8e6492..3df4d46 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -727,8 +727,6 @@ static inline struct sched_entity *parent_entity(struct sched_entity *se)
return se->parent;
}

-#define GROUP_IMBALANCE_PCT 20
-
#else /* CONFIG_FAIR_GROUP_SCHED */

#define for_each_sched_entity(se) \
@@ -819,26 +817,15 @@ hrtick_start_fair(struct rq *rq, struct task_struct *p)
static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
{
struct cfs_rq *cfs_rq;
- struct sched_entity *se = &p->se,
- *topse = NULL; /* Highest schedulable entity */
- int incload = 1;
+ struct sched_entity *se = &p->se;

for_each_sched_entity(se) {
- topse = se;
- if (se->on_rq) {
- incload = 0;
+ if (se->on_rq)
break;
- }
cfs_rq = cfs_rq_of(se);
enqueue_entity(cfs_rq, se, wakeup);
wakeup = 1;
}
- /* Increment cpu load if we just enqueued the first task of a group on
- * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs
- * at the highest grouping level.
- */
- if (incload)
- inc_cpu_load(rq, topse->load.weight);

hrtick_start_fair(rq, rq->curr);
}
@@ -851,28 +838,16 @@ static void enqueue_task_fair(struct rq *rq, struct task_struct *p, int wakeup)
static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int sleep)
{
struct cfs_rq *cfs_rq;
- struct sched_entity *se = &p->se,
- *topse = NULL; /* Highest schedulable entity */
- int decload = 1;
+ struct sched_entity *se = &p->se;

for_each_sched_entity(se) {
- topse = se;
cfs_rq = cfs_rq_of(se);
dequeue_entity(cfs_rq, se, sleep);
/* Don't dequeue parent if it has other entities besides us */
- if (cfs_rq->load.weight) {
- if (parent_entity(se))
- decload = 0;
+ if (cfs_rq->load.weight)
break;
- }
sleep = 1;
}
- /* Decrement cpu load if we just dequeued the last task of a group on
- * 'rq->cpu'. 'topse' represents the group to which task 'p' belongs
- * at the highest grouping level.
- */
- if (decload)
- dec_cpu_load(rq, topse->load.weight);

hrtick_start_fair(rq, rq->curr);
}
@@ -1186,6 +1161,25 @@ static struct task_struct *load_balance_next_fair(void *arg)
return __load_balance_iterator(cfs_rq, cfs_rq->rb_load_balance_curr);
}

+#ifdef CONFIG_FAIR_GROUP_SCHED
+static int cfs_rq_best_prio(struct cfs_rq *cfs_rq)
+{
+ struct sched_entity *curr;
+ struct task_struct *p;
+
+ if (!cfs_rq->nr_running || !first_fair(cfs_rq))
+ return MAX_PRIO;
+
+ curr = cfs_rq->curr;
+ if (!curr)
+ curr = __pick_next_entity(cfs_rq);
+
+ p = task_of(curr);
+
+ return p->prio;
+}
+#endif
+
static unsigned long
load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
unsigned long max_load_move,
@@ -1195,45 +1189,28 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
struct cfs_rq *busy_cfs_rq;
long rem_load_move = max_load_move;
struct rq_iterator cfs_rq_iterator;
- unsigned long load_moved;

cfs_rq_iterator.start = load_balance_start_fair;
cfs_rq_iterator.next = load_balance_next_fair;

for_each_leaf_cfs_rq(busiest, busy_cfs_rq) {
#ifdef CONFIG_FAIR_GROUP_SCHED
- struct cfs_rq *this_cfs_rq = busy_cfs_rq->tg->cfs_rq[this_cpu];
- unsigned long maxload, task_load, group_weight;
- unsigned long thisload, per_task_load;
- struct sched_entity *se = busy_cfs_rq->tg->se[busiest->cpu];
-
- task_load = busy_cfs_rq->load.weight;
- group_weight = se->load.weight;
+ struct cfs_rq *this_cfs_rq;
+ long imbalance;
+ unsigned long maxload;

- /*
- * 'group_weight' is contributed by tasks of total weight
- * 'task_load'. To move 'rem_load_move' worth of weight only,
- * we need to move a maximum task load of:
- *
- * maxload = (remload / group_weight) * task_load;
- */
- maxload = (rem_load_move * task_load) / group_weight;
+ this_cfs_rq = cpu_cfs_rq(busy_cfs_rq, this_cpu);

- if (!maxload || !task_load)
+ imbalance = busy_cfs_rq->load.weight - this_cfs_rq->load.weight;
+ /* Don't pull if this_cfs_rq has more load than busy_cfs_rq */
+ if (imbalance <= 0)
continue;

- per_task_load = task_load / busy_cfs_rq->nr_running;
- /*
- * balance_tasks will try to forcibly move atleast one task if
- * possible (because of SCHED_LOAD_SCALE_FUZZ). Avoid that if
- * maxload is less than GROUP_IMBALANCE_FUZZ% the per_task_load.
- */
- if (100 * maxload < GROUP_IMBALANCE_PCT * per_task_load)
- continue;
+ /* Don't pull more than imbalance/2 */
+ imbalance /= 2;
+ maxload = min(rem_load_move, imbalance);

- /* Disable priority-based load balance */
- *this_best_prio = 0;
- thisload = this_cfs_rq->load.weight;
+ *this_best_prio = cfs_rq_best_prio(this_cfs_rq);
#else
# define maxload rem_load_move
#endif
@@ -1242,33 +1219,11 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
* load_balance_[start|next]_fair iterators
*/
cfs_rq_iterator.arg = busy_cfs_rq;
- load_moved = balance_tasks(this_rq, this_cpu, busiest,
+ rem_load_move -= balance_tasks(this_rq, this_cpu, busiest,
maxload, sd, idle, all_pinned,
this_best_prio,
&cfs_rq_iterator);

-#ifdef CONFIG_FAIR_GROUP_SCHED
- /*
- * load_moved holds the task load that was moved. The
- * effective (group) weight moved would be:
- * load_moved_eff = load_moved/task_load * group_weight;
- */
- load_moved = (group_weight * load_moved) / task_load;
-
- /* Adjust shares on both cpus to reflect load_moved */
- group_weight -= load_moved;
- set_se_shares(se, group_weight);
-
- se = busy_cfs_rq->tg->se[this_cpu];
- if (!thisload)
- group_weight = load_moved;
- else
- group_weight = se->load.weight + load_moved;
- set_se_shares(se, group_weight);
-#endif
-
- rem_load_move -= load_moved;
-
if (rem_load_move <= 0)
break;
}
diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
index f54792b..76e8285 100644
--- a/kernel/sched_rt.c
+++ b/kernel/sched_rt.c
@@ -393,8 +393,6 @@ static void enqueue_task_rt(struct rq *rq, struct task_struct *p, int wakeup)
*/
for_each_sched_rt_entity(rt_se)
enqueue_rt_entity(rt_se);
-
- inc_cpu_load(rq, p->se.load.weight);
}

static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
@@ -414,8 +412,6 @@ static void dequeue_task_rt(struct rq *rq, struct task_struct *p, int sleep)
if (rt_rq && rt_rq->rt_nr_running)
enqueue_rt_entity(rt_se);
}
-
- dec_cpu_load(rq, p->se.load.weight);
}

/*
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 8b7e954..b2a2d68 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -311,24 +311,6 @@ static struct ctl_table kern_table[] = {
.mode = 0644,
.proc_handler = &proc_dointvec,
},
-#if defined(CONFIG_FAIR_GROUP_SCHED) && defined(CONFIG_SMP)
- {
- .ctl_name = CTL_UNNUMBERED,
- .procname = "sched_min_bal_int_shares",
- .data = &sysctl_sched_min_bal_int_shares,
- .maxlen = sizeof(unsigned int),
- .mode = 0644,
- .proc_handler = &proc_dointvec,
- },
- {
- .ctl_name = CTL_UNNUMBERED,
- .procname = "sched_max_bal_int_shares",
- .data = &sysctl_sched_max_bal_int_shares,
- .maxlen = sizeof(unsigned int),
- .mode = 0644,
- .proc_handler = &proc_dointvec,
- },
-#endif
#endif
{
.ctl_name = CTL_UNNUMBERED,