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sched: Fix load-balance wreckage
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
Ingo Molnar
parent
2e5b5b3a1b
commit
5d6523ebd2
@ -784,7 +784,7 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
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#ifdef CONFIG_SMP
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if (entity_is_task(se))
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list_add(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
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list_add_tail(&se->group_node, &rq_of(cfs_rq)->cfs_tasks);
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#endif
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cfs_rq->nr_running++;
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}
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@ -3071,7 +3071,6 @@ static unsigned long __read_mostly max_load_balance_interval = HZ/10;
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#define LBF_ALL_PINNED 0x01
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#define LBF_NEED_BREAK 0x02
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#define LBF_ABORT 0x04
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struct lb_env {
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struct sched_domain *sd;
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@ -3083,7 +3082,7 @@ struct lb_env {
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struct rq *dst_rq;
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enum cpu_idle_type idle;
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unsigned long max_load_move;
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long load_move;
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unsigned int flags;
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unsigned int loop;
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@ -3216,39 +3215,47 @@ static int move_one_task(struct lb_env *env)
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static unsigned long task_h_load(struct task_struct *p);
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static unsigned long balance_tasks(struct lb_env *env)
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/*
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* move_tasks tries to move up to load_move weighted load from busiest to
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* this_rq, as part of a balancing operation within domain "sd".
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* Returns 1 if successful and 0 otherwise.
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*
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* Called with both runqueues locked.
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*/
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static int move_tasks(struct lb_env *env)
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{
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long rem_load_move = env->max_load_move;
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struct task_struct *p, *n;
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struct list_head *tasks = &env->src_rq->cfs_tasks;
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struct task_struct *p;
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unsigned long load;
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int pulled = 0;
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if (env->max_load_move == 0)
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goto out;
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if (env->load_move <= 0)
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return 0;
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while (!list_empty(tasks)) {
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p = list_first_entry(tasks, struct task_struct, se.group_node);
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list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
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env->loop++;
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/* We've more or less seen every task there is, call it quits */
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if (env->loop > env->loop_max) {
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env->flags |= LBF_ABORT;
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if (env->loop > env->loop_max)
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break;
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}
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/* take a beather every nr_migrate tasks */
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/* take a breather every nr_migrate tasks */
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if (env->loop > env->loop_break) {
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env->loop_break += sysctl_sched_nr_migrate;
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env->flags |= LBF_NEED_BREAK;
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break;
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}
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if (throttled_lb_pair(task_group(p), env->src_rq->cpu,
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env->dst_cpu))
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if (throttled_lb_pair(task_group(p), env->src_cpu, env->dst_cpu))
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goto next;
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load = task_h_load(p);
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if (load < 16 && !env->sd->nr_balance_failed)
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goto next;
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if ((load * 2) > rem_load_move)
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if ((load / 2) > env->load_move)
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goto next;
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if (!can_migrate_task(p, env))
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@ -3256,7 +3263,7 @@ static unsigned long balance_tasks(struct lb_env *env)
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move_task(p, env);
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pulled++;
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rem_load_move -= load;
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env->load_move -= load;
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#ifdef CONFIG_PREEMPT
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/*
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@ -3264,24 +3271,22 @@ static unsigned long balance_tasks(struct lb_env *env)
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* kernels will stop after the first task is pulled to minimize
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* the critical section.
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*/
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if (env->idle == CPU_NEWLY_IDLE) {
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env->flags |= LBF_ABORT;
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if (env->idle == CPU_NEWLY_IDLE)
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break;
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}
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#endif
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/*
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* We only want to steal up to the prescribed amount of
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* weighted load.
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*/
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if (rem_load_move <= 0)
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if (env->load_move <= 0)
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break;
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continue;
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next:
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list_move_tail(&p->se.group_node, &env->src_rq->cfs_tasks);
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list_move_tail(&p->se.group_node, tasks);
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}
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out:
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/*
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* Right now, this is one of only two places move_task() is called,
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* so we can safely collect move_task() stats here rather than
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@ -3289,7 +3294,7 @@ static unsigned long balance_tasks(struct lb_env *env)
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*/
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schedstat_add(env->sd, lb_gained[env->idle], pulled);
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return env->max_load_move - rem_load_move;
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return pulled;
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}
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#ifdef CONFIG_FAIR_GROUP_SCHED
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@ -3399,43 +3404,6 @@ static unsigned long task_h_load(struct task_struct *p)
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}
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#endif
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/*
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* move_tasks tries to move up to max_load_move weighted load from busiest to
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* this_rq, as part of a balancing operation within domain "sd".
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* Returns 1 if successful and 0 otherwise.
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*
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* Called with both runqueues locked.
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*/
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static int move_tasks(struct lb_env *env)
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{
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unsigned long max_load_move = env->max_load_move;
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unsigned long total_load_moved = 0, load_moved;
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update_h_load(cpu_of(env->src_rq));
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do {
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env->max_load_move = max_load_move - total_load_moved;
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load_moved = balance_tasks(env);
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total_load_moved += load_moved;
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if (env->flags & (LBF_NEED_BREAK|LBF_ABORT))
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break;
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#ifdef CONFIG_PREEMPT
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/*
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* NEWIDLE balancing is a source of latency, so preemptible
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* kernels will stop after the first task is pulled to minimize
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* the critical section.
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*/
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if (env->idle == CPU_NEWLY_IDLE && env->dst_rq->nr_running) {
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env->flags |= LBF_ABORT;
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break;
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}
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#endif
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} while (load_moved && max_load_move > total_load_moved);
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return total_load_moved > 0;
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}
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/********** Helpers for find_busiest_group ************************/
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/*
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* sd_lb_stats - Structure to store the statistics of a sched_domain
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@ -4477,31 +4445,31 @@ static int load_balance(int this_cpu, struct rq *this_rq,
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* correctly treated as an imbalance.
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*/
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env.flags |= LBF_ALL_PINNED;
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env.max_load_move = imbalance;
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env.load_move = imbalance;
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env.src_cpu = busiest->cpu;
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env.src_rq = busiest;
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env.loop_max = busiest->nr_running;
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more_balance:
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local_irq_save(flags);
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double_rq_lock(this_rq, busiest);
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ld_moved = move_tasks(&env);
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if (!env.loop)
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update_h_load(env.src_cpu);
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ld_moved += move_tasks(&env);
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double_rq_unlock(this_rq, busiest);
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local_irq_restore(flags);
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if (env.flags & LBF_NEED_BREAK) {
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env.flags &= ~LBF_NEED_BREAK;
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goto more_balance;
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}
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/*
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* some other cpu did the load balance for us.
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*/
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if (ld_moved && this_cpu != smp_processor_id())
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resched_cpu(this_cpu);
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if (env.flags & LBF_ABORT)
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goto out_balanced;
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if (env.flags & LBF_NEED_BREAK) {
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env.flags &= ~LBF_NEED_BREAK;
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goto redo;
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}
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/* All tasks on this runqueue were pinned by CPU affinity */
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if (unlikely(env.flags & LBF_ALL_PINNED)) {
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cpumask_clear_cpu(cpu_of(busiest), cpus);
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