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sched: fix sched_domain aggregation
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Keeping the aggregate on the first cpu of the sched domain has two problems:
 - it could collide between different sched domains on different cpus
 - it could slow things down because of the remote accesses

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Peter Zijlstra authored and Ingo Molnar committed Jun 27, 2008
1 parent 32df2ee commit b6a86c7
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Showing 3 changed files with 60 additions and 66 deletions.
1 change: 0 additions & 1 deletion include/linux/sched.h
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Original file line number Diff line number Diff line change
Expand Up @@ -765,7 +765,6 @@ struct sched_domain {
struct sched_domain *child; /* bottom domain must be null terminated */
struct sched_group *groups; /* the balancing groups of the domain */
cpumask_t span; /* span of all CPUs in this domain */
int first_cpu; /* cache of the first cpu in this domain */
unsigned long min_interval; /* Minimum balance interval ms */
unsigned long max_interval; /* Maximum balance interval ms */
unsigned int busy_factor; /* less balancing by factor if busy */
Expand Down
113 changes: 54 additions & 59 deletions kernel/sched.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1480,35 +1480,35 @@ static int task_hot(struct task_struct *p, u64 now, struct sched_domain *sd);
*/

static inline struct aggregate_struct *
aggregate(struct task_group *tg, struct sched_domain *sd)
aggregate(struct task_group *tg, int cpu)
{
return &tg->cfs_rq[sd->first_cpu]->aggregate;
return &tg->cfs_rq[cpu]->aggregate;
}

typedef void (*aggregate_func)(struct task_group *, struct sched_domain *);
typedef void (*aggregate_func)(struct task_group *, int, struct sched_domain *);

/*
* Iterate the full tree, calling @down when first entering a node and @up when
* leaving it for the final time.
*/
static
void aggregate_walk_tree(aggregate_func down, aggregate_func up,
struct sched_domain *sd)
int cpu, struct sched_domain *sd)
{
struct task_group *parent, *child;

rcu_read_lock();
parent = &root_task_group;
down:
(*down)(parent, sd);
(*down)(parent, cpu, sd);
list_for_each_entry_rcu(child, &parent->children, siblings) {
parent = child;
goto down;

up:
continue;
}
(*up)(parent, sd);
(*up)(parent, cpu, sd);

child = parent;
parent = parent->parent;
Expand All @@ -1520,8 +1520,8 @@ void aggregate_walk_tree(aggregate_func down, aggregate_func up,
/*
* Calculate the aggregate runqueue weight.
*/
static
void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_group_weight(struct task_group *tg, int cpu, struct sched_domain *sd)
{
unsigned long rq_weight = 0;
unsigned long task_weight = 0;
Expand All @@ -1532,34 +1532,34 @@ void aggregate_group_weight(struct task_group *tg, struct sched_domain *sd)
task_weight += tg->cfs_rq[i]->task_weight;
}

aggregate(tg, sd)->rq_weight = rq_weight;
aggregate(tg, sd)->task_weight = task_weight;
aggregate(tg, cpu)->rq_weight = rq_weight;
aggregate(tg, cpu)->task_weight = task_weight;
}

/*
* Compute the weight of this group on the given cpus.
*/
static
void aggregate_group_shares(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
{
unsigned long shares = 0;
int i;

for_each_cpu_mask(i, sd->span)
shares += tg->cfs_rq[i]->shares;

if ((!shares && aggregate(tg, sd)->rq_weight) || shares > tg->shares)
if ((!shares && aggregate(tg, cpu)->rq_weight) || shares > tg->shares)
shares = tg->shares;

aggregate(tg, sd)->shares = shares;
aggregate(tg, cpu)->shares = shares;
}

/*
* Compute the load fraction assigned to this group, relies on the aggregate
* weight and this group's parent's load, i.e. top-down.
*/
static
void aggregate_group_load(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_group_load(struct task_group *tg, int cpu, struct sched_domain *sd)
{
unsigned long load;

Expand All @@ -1571,17 +1571,17 @@ void aggregate_group_load(struct task_group *tg, struct sched_domain *sd)
load += cpu_rq(i)->load.weight;

} else {
load = aggregate(tg->parent, sd)->load;
load = aggregate(tg->parent, cpu)->load;

/*
* shares is our weight in the parent's rq so
* shares/parent->rq_weight gives our fraction of the load
*/
load *= aggregate(tg, sd)->shares;
load /= aggregate(tg->parent, sd)->rq_weight + 1;
load *= aggregate(tg, cpu)->shares;
load /= aggregate(tg->parent, cpu)->rq_weight + 1;
}

aggregate(tg, sd)->load = load;
aggregate(tg, cpu)->load = load;
}

static void __set_se_shares(struct sched_entity *se, unsigned long shares);
Expand All @@ -1590,8 +1590,8 @@ static void __set_se_shares(struct sched_entity *se, unsigned long shares);
* Calculate and set the cpu's group shares.
*/
static void
__update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
int tcpu)
__update_group_shares_cpu(struct task_group *tg, int cpu,
struct sched_domain *sd, int tcpu)
{
int boost = 0;
unsigned long shares;
Expand All @@ -1618,8 +1618,8 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
* \Sum rq_weight
*
*/
shares = aggregate(tg, sd)->shares * rq_weight;
shares /= aggregate(tg, sd)->rq_weight + 1;
shares = aggregate(tg, cpu)->shares * rq_weight;
shares /= aggregate(tg, cpu)->rq_weight + 1;

/*
* record the actual number of shares, not the boosted amount.
Expand All @@ -1639,15 +1639,15 @@ __update_group_shares_cpu(struct task_group *tg, struct sched_domain *sd,
* task went to.
*/
static void
__move_group_shares(struct task_group *tg, struct sched_domain *sd,
__move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
int scpu, int dcpu)
{
unsigned long shares;

shares = tg->cfs_rq[scpu]->shares + tg->cfs_rq[dcpu]->shares;

__update_group_shares_cpu(tg, sd, scpu);
__update_group_shares_cpu(tg, sd, dcpu);
__update_group_shares_cpu(tg, cpu, sd, scpu);
__update_group_shares_cpu(tg, cpu, sd, dcpu);

/*
* ensure we never loose shares due to rounding errors in the
Expand All @@ -1663,62 +1663,62 @@ __move_group_shares(struct task_group *tg, struct sched_domain *sd,
* we need to walk up the tree and change all shares until we hit the root.
*/
static void
move_group_shares(struct task_group *tg, struct sched_domain *sd,
move_group_shares(struct task_group *tg, int cpu, struct sched_domain *sd,
int scpu, int dcpu)
{
while (tg) {
__move_group_shares(tg, sd, scpu, dcpu);
__move_group_shares(tg, cpu, sd, scpu, dcpu);
tg = tg->parent;
}
}

static
void aggregate_group_set_shares(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_group_set_shares(struct task_group *tg, int cpu, struct sched_domain *sd)
{
unsigned long shares = aggregate(tg, sd)->shares;
unsigned long shares = aggregate(tg, cpu)->shares;
int i;

for_each_cpu_mask(i, sd->span) {
struct rq *rq = cpu_rq(i);
unsigned long flags;

spin_lock_irqsave(&rq->lock, flags);
__update_group_shares_cpu(tg, sd, i);
__update_group_shares_cpu(tg, cpu, sd, i);
spin_unlock_irqrestore(&rq->lock, flags);
}

aggregate_group_shares(tg, sd);
aggregate_group_shares(tg, cpu, sd);

/*
* ensure we never loose shares due to rounding errors in the
* above redistribution.
*/
shares -= aggregate(tg, sd)->shares;
shares -= aggregate(tg, cpu)->shares;
if (shares) {
tg->cfs_rq[sd->first_cpu]->shares += shares;
aggregate(tg, sd)->shares += shares;
tg->cfs_rq[cpu]->shares += shares;
aggregate(tg, cpu)->shares += shares;
}
}

/*
* Calculate the accumulative weight and recursive load of each task group
* while walking down the tree.
*/
static
void aggregate_get_down(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_get_down(struct task_group *tg, int cpu, struct sched_domain *sd)
{
aggregate_group_weight(tg, sd);
aggregate_group_shares(tg, sd);
aggregate_group_load(tg, sd);
aggregate_group_weight(tg, cpu, sd);
aggregate_group_shares(tg, cpu, sd);
aggregate_group_load(tg, cpu, sd);
}

/*
* Rebalance the cpu shares while walking back up the tree.
*/
static
void aggregate_get_up(struct task_group *tg, struct sched_domain *sd)
static void
aggregate_get_up(struct task_group *tg, int cpu, struct sched_domain *sd)
{
aggregate_group_set_shares(tg, sd);
aggregate_group_set_shares(tg, cpu, sd);
}

static DEFINE_PER_CPU(spinlock_t, aggregate_lock);
Expand All @@ -1731,18 +1731,18 @@ static void __init init_aggregate(void)
spin_lock_init(&per_cpu(aggregate_lock, i));
}

static int get_aggregate(struct sched_domain *sd)
static int get_aggregate(int cpu, struct sched_domain *sd)
{
if (!spin_trylock(&per_cpu(aggregate_lock, sd->first_cpu)))
if (!spin_trylock(&per_cpu(aggregate_lock, cpu)))
return 0;

aggregate_walk_tree(aggregate_get_down, aggregate_get_up, sd);
aggregate_walk_tree(aggregate_get_down, aggregate_get_up, cpu, sd);
return 1;
}

static void put_aggregate(struct sched_domain *sd)
static void put_aggregate(int cpu, struct sched_domain *sd)
{
spin_unlock(&per_cpu(aggregate_lock, sd->first_cpu));
spin_unlock(&per_cpu(aggregate_lock, cpu));
}

static void cfs_rq_set_shares(struct cfs_rq *cfs_rq, unsigned long shares)
Expand All @@ -1756,12 +1756,12 @@ static inline void init_aggregate(void)
{
}

static inline int get_aggregate(struct sched_domain *sd)
static inline int get_aggregate(int cpu, struct sched_domain *sd)
{
return 0;
}

static inline void put_aggregate(struct sched_domain *sd)
static inline void put_aggregate(int cpu, struct sched_domain *sd)
{
}
#endif
Expand Down Expand Up @@ -3539,7 +3539,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,

cpus_setall(*cpus);

unlock_aggregate = get_aggregate(sd);
unlock_aggregate = get_aggregate(this_cpu, sd);

/*
* When power savings policy is enabled for the parent domain, idle
Expand Down Expand Up @@ -3678,7 +3678,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
ld_moved = 0;
out:
if (unlock_aggregate)
put_aggregate(sd);
put_aggregate(this_cpu, sd);
return ld_moved;
}

Expand Down Expand Up @@ -7292,7 +7292,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
SD_INIT(sd, ALLNODES);
set_domain_attribute(sd, attr);
sd->span = *cpu_map;
sd->first_cpu = first_cpu(sd->span);
cpu_to_allnodes_group(i, cpu_map, &sd->groups, tmpmask);
p = sd;
sd_allnodes = 1;
Expand All @@ -7303,7 +7302,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
SD_INIT(sd, NODE);
set_domain_attribute(sd, attr);
sched_domain_node_span(cpu_to_node(i), &sd->span);
sd->first_cpu = first_cpu(sd->span);
sd->parent = p;
if (p)
p->child = sd;
Expand All @@ -7315,7 +7313,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
SD_INIT(sd, CPU);
set_domain_attribute(sd, attr);
sd->span = *nodemask;
sd->first_cpu = first_cpu(sd->span);
sd->parent = p;
if (p)
p->child = sd;
Expand All @@ -7327,7 +7324,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
SD_INIT(sd, MC);
set_domain_attribute(sd, attr);
sd->span = cpu_coregroup_map(i);
sd->first_cpu = first_cpu(sd->span);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
Expand All @@ -7340,7 +7336,6 @@ static int __build_sched_domains(const cpumask_t *cpu_map,
SD_INIT(sd, SIBLING);
set_domain_attribute(sd, attr);
sd->span = per_cpu(cpu_sibling_map, i);
sd->first_cpu = first_cpu(sd->span);
cpus_and(sd->span, sd->span, *cpu_map);
sd->parent = p;
p->child = sd;
Expand Down
12 changes: 6 additions & 6 deletions kernel/sched_fair.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1429,11 +1429,11 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
/*
* empty group
*/
if (!aggregate(tg, sd)->task_weight)
if (!aggregate(tg, this_cpu)->task_weight)
continue;

rem_load = rem_load_move * aggregate(tg, sd)->rq_weight;
rem_load /= aggregate(tg, sd)->load + 1;
rem_load = rem_load_move * aggregate(tg, this_cpu)->rq_weight;
rem_load /= aggregate(tg, this_cpu)->load + 1;

this_weight = tg->cfs_rq[this_cpu]->task_weight;
busiest_weight = tg->cfs_rq[busiest_cpu]->task_weight;
Expand All @@ -1451,10 +1451,10 @@ load_balance_fair(struct rq *this_rq, int this_cpu, struct rq *busiest,
if (!moved_load)
continue;

move_group_shares(tg, sd, busiest_cpu, this_cpu);
move_group_shares(tg, this_cpu, sd, busiest_cpu, this_cpu);

moved_load *= aggregate(tg, sd)->load;
moved_load /= aggregate(tg, sd)->rq_weight + 1;
moved_load *= aggregate(tg, this_cpu)->load;
moved_load /= aggregate(tg, this_cpu)->rq_weight + 1;

rem_load_move -= moved_load;
if (rem_load_move < 0)
Expand Down

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