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sched: Fix load-balance wreckage

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Commit 367456c ("sched: Ditch per cgroup task lists for
load-balancing") completely wrecked load-balancing due to
a few silly mistakes.

Correct those and remove more pointless code.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-zk04ihygwxn7qqrlpaf73b0r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2012-03-10 00:07:36 +01:00 committed by Ingo Molnar
parent 2e5b5b3a1b
commit 5d6523ebd2
1 changed files with 39 additions and 71 deletions
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110
kernel/sched/fair.c
View file

@ -784,7 +784,7 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
#ifdef CONFIG_SMP
if (entity_is_task(se))
list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
list_add_tail(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
#endif
cfs_rq->nr_running++;
}
@ -3071,7 +3071,6 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10;
#define LBF_ALL_PINNED 0x01
#define LBF_NEED_BREAK 0x02
#define LBF_ABORT 0x04
struct lb_env {
struct sched_domain *sd;
@ -3083,7 +3082,7 @@ struct lb_env {
struct rq *dst_rq;
enum cpu_idle_type idle;
unsigned long max_load_move;
long load_move;
unsigned int flags;
unsigned int loop;
@ -3216,39 +3215,47 @@ static int move_one_task(struct lb_env *env)
static unsigned long task_h_load(struct task_struct *p);
static unsigned long balance_tasks(struct lb_env *env)
/*
* move_tasks tries to move up to load_move weighted load from busiest to
* this_rq, as part of a balancing operation within domain "sd".
* Returns 1 if successful and 0 otherwise.
*
* Called with both runqueues locked.
*/
static int move_tasks(struct lb_env *env)
{
long rem_load_move = env->max_load_move;
struct task_struct *p, *n;
struct list_head *tasks = &env->src_rq->cfs_tasks;
struct task_struct *p;
unsigned long load;
int pulled = 0;
if (env->max_load_move == 0)
goto out;
if (env->load_move <= 0)
return 0;
while (!list_empty(tasks)) {
p = list_first_entry(tasks, struct task_struct, se.group_node);
list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
env->loop++;
/* We've more or less seen every task there is, call it quits */
if (env->loop > env->loop_max) {
env->flags |= LBF_ABORT;
if (env->loop > env->loop_max)
break;
}
/* take a beather every nr_migrate tasks */
/* take a breather every nr_migrate tasks */
if (env->loop > env->loop_break) {
env->loop_break += sysctl_sched_nr_migrate;
env->flags |= LBF_NEED_BREAK;
break;
}
if (throttled_lb_pair(task_group(p), env->src_rq->cpu,
env->dst_cpu))
if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
goto next;
load = task_h_load(p);
if (load < 16 && !env->sd->nr_balance_failed)
goto next;
if ((load * 2) > rem_load_move)
if ((load / 2) > env->load_move)
goto next;
if (!can_migrate_task(p, env))
@ -3256,7 +3263,7 @@ static unsigned long balance_tasks(struct lb_env *env)
move_task(p, env);
pulled++;
rem_load_move -= load;
env->load_move -= load;
#ifdef CONFIG_PREEMPT
/*
@ -3264,24 +3271,22 @@ static unsigned long balance_tasks(struct lb_env *env)
* kernels will stop after the first task is pulled to minimize
* the critical section.
*/
if (env->idle == CPU_NEWLY_IDLE) {
env->flags |= LBF_ABORT;
if (env->idle == CPU_NEWLY_IDLE)
break;
}
#endif
/*
* We only want to steal up to the prescribed amount of
* weighted load.
*/
if (rem_load_move <= 0)
if (env->load_move <= 0)
break;
continue;
next:
list_move_tail(&p->se.group_node, &env->src_rq->cfs_tasks);
list_move_tail(&p->se.group_node, tasks);
}
out:
/*
* Right now, this is one of only two places move_task() is called,
* so we can safely collect move_task() stats here rather than
@ -3289,7 +3294,7 @@ static unsigned long balance_tasks(struct lb_env *env)
*/
schedstat_add(env->sd, lb_gained[env->idle], pulled);
return env->max_load_move - rem_load_move;
return pulled;
}
#ifdef CONFIG_FAIR_GROUP_SCHED
@ -3399,43 +3404,6 @@ static unsigned long task_h_load(struct task_struct *p)
}
#endif
/*
* move_tasks tries to move up to max_load_move weighted load from busiest to
* this_rq, as part of a balancing operation within domain "sd".
* Returns 1 if successful and 0 otherwise.
*
* Called with both runqueues locked.
*/
static int move_tasks(struct lb_env *env)
{
unsigned long max_load_move = env->max_load_move;
unsigned long total_load_moved = 0, load_moved;
update_h_load(cpu_of(env->src_rq));
do {
env->max_load_move = max_load_move - total_load_moved;
load_moved = balance_tasks(env);
total_load_moved += load_moved;
if (env->flags & (LBF_NEED_BREAK|LBF_ABORT))
break;
#ifdef CONFIG_PREEMPT
/*
* NEWIDLE balancing is a source of latency, so preemptible
* kernels will stop after the first task is pulled to minimize
* the critical section.
*/
if (env->idle == CPU_NEWLY_IDLE && env->dst_rq->nr_running) {
env->flags |= LBF_ABORT;
break;
}
#endif
} while (load_moved && max_load_move > total_load_moved);
return total_load_moved > 0;
}
/********** Helpers for find_busiest_group ************************/
/*
* sd_lb_stats - Structure to store the statistics of a sched_domain
@ -4477,31 +4445,31 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* correctly treated as an imbalance.
*/
env.flags |= LBF_ALL_PINNED;
env.max_load_move = imbalance;
env.load_move = imbalance;
env.src_cpu = busiest->cpu;
env.src_rq = busiest;
env.loop_max = busiest->nr_running;
more_balance:
local_irq_save(flags);
double_rq_lock(this_rq, busiest);
ld_moved = move_tasks(&env);
if (!env.loop)
update_h_load(env.src_cpu);
ld_moved += move_tasks(&env);
double_rq_unlock(this_rq, busiest);
local_irq_restore(flags);
if (env.flags & LBF_NEED_BREAK) {
env.flags &= ~LBF_NEED_BREAK;
goto more_balance;
}
/*
* some other cpu did the load balance for us.
*/
if (ld_moved && this_cpu != smp_processor_id())
resched_cpu(this_cpu);
if (env.flags & LBF_ABORT)
goto out_balanced;
if (env.flags & LBF_NEED_BREAK) {
env.flags &= ~LBF_NEED_BREAK;
goto redo;
}
/* All tasks on this runqueue were pinned by CPU affinity */
if (unlikely(env.flags & LBF_ALL_PINNED)) {
cpumask_clear_cpu(cpu_of(busiest), cpus);