sched: Ditch per cgroup task lists for load-balancing
Per cgroup load-balance has numerous problems, chief amongst them that there is no real sane order in them. So stop pretending it makes sense and enqueue all tasks on a single list. This also allows us to more easily fix the fwd progress issue uncovered by the lock-break stuff. Rotate the list on failure to migreate and limit the total iterations to nr_running (which with releasing the lock isn't strictly accurate but close enough). Also add a filter that skips very light tasks on the first attempt around the list, this attempts to avoid shooting whole cgroups around without affecting over balance. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: pjt@google.com Link: http://lkml.kernel.org/n/tip-tx8yqydc7eimgq7i4rkc3a4g@git.kernel.org Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra
Ingo Molnar
Родитель
ddcdf6e7d9
Коммит
367456c756
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@ -6959,6 +6959,9 @@ void __init sched_init(void)
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rq->online = 0;
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rq->idle_stamp = 0;
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rq->avg_idle = 2*sysctl_sched_migration_cost;
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INIT_LIST_HEAD(&rq->cfs_tasks);
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rq_attach_root(rq, &def_root_domain);
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#ifdef CONFIG_NO_HZ
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rq->nohz_flags = 0;
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@ -776,29 +776,16 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
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* Scheduling class queueing methods:
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*/
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#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
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static void
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add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
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{
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cfs_rq->task_weight += weight;
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}
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#else
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static inline void
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add_cfs_task_weight(struct cfs_rq *cfs_rq, unsigned long weight)
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{
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}
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#endif
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static void
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account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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{
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update_load_add(&cfs_rq->load, se->load.weight);
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if (!parent_entity(se))
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update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
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if (entity_is_task(se)) {
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add_cfs_task_weight(cfs_rq, se->load.weight);
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list_add(&se->group_node, &cfs_rq->tasks);
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}
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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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#endif
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cfs_rq->nr_running++;
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}
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@ -808,10 +795,8 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
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update_load_sub(&cfs_rq->load, se->load.weight);
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if (!parent_entity(se))
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update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
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if (entity_is_task(se)) {
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add_cfs_task_weight(cfs_rq, -se->load.weight);
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if (entity_is_task(se))
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list_del_init(&se->group_node);
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}
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cfs_rq->nr_running--;
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}
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@ -3085,17 +3070,14 @@ static bool yield_to_task_fair(struct rq *rq, struct task_struct *p, bool preemp
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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 /* clears into HAD_BREAK */
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#define LBF_HAD_BREAK 0x04
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#define LBF_HAD_BREAKS 0x0C /* count HAD_BREAKs overflows into ABORT */
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#define LBF_ABORT 0x10
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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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int src_cpu;
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struct rq *src_rq;
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struct cfs_rq *src_cfs_rq;
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int dst_cpu;
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struct rq *dst_rq;
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@ -3103,6 +3085,10 @@ struct lb_env {
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enum cpu_idle_type idle;
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unsigned long max_load_move;
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unsigned int flags;
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unsigned int loop;
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unsigned int loop_break;
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unsigned int loop_max;
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};
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/*
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@ -3208,53 +3194,69 @@ int can_migrate_task(struct task_struct *p, struct lb_env *env)
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static int move_one_task(struct lb_env *env)
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{
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struct task_struct *p, *n;
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struct cfs_rq *cfs_rq;
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for_each_leaf_cfs_rq(env->src_rq, cfs_rq) {
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list_for_each_entry_safe(p, n, &cfs_rq->tasks, se.group_node) {
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if (throttled_lb_pair(task_group(p),
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env->src_cpu, env->dst_cpu))
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break;
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list_for_each_entry_safe(p, n, &env->src_rq->cfs_tasks, se.group_node) {
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if (throttled_lb_pair(task_group(p), env->src_rq->cpu, env->dst_cpu))
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continue;
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if (!can_migrate_task(p, env))
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continue;
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if (!can_migrate_task(p, env))
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continue;
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move_task(p, env);
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/*
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* Right now, this is only the second place move_task()
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* is called, so we can safely collect move_task()
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* stats here rather than inside move_task().
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*/
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schedstat_inc(env->sd, lb_gained[env->idle]);
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return 1;
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}
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move_task(p, env);
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/*
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* Right now, this is only the second place move_task()
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* is called, so we can safely collect move_task()
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* stats here rather than inside move_task().
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*/
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schedstat_inc(env->sd, lb_gained[env->idle]);
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return 1;
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}
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return 0;
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}
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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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int loops = 0, pulled = 0;
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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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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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list_for_each_entry_safe(p, n, &env->src_cfs_rq->tasks, se.group_node) {
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if (loops++ > sysctl_sched_nr_migrate) {
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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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break;
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}
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/* take a beather 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 ((p->se.load.weight >> 1) > rem_load_move ||
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!can_migrate_task(p, env))
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continue;
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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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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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goto next;
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if (!can_migrate_task(p, env))
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goto next;
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move_task(p, env);
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pulled++;
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rem_load_move -= p->se.load.weight;
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rem_load_move -= load;
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#ifdef CONFIG_PREEMPT
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/*
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@ -3274,6 +3276,10 @@ static unsigned long balance_tasks(struct lb_env *env)
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*/
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if (rem_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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}
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out:
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/*
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@ -3363,65 +3369,33 @@ static int tg_load_down(struct task_group *tg, void *data)
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static void update_h_load(long cpu)
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{
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rcu_read_lock();
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walk_tg_tree(tg_load_down, tg_nop, (void *)cpu);
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rcu_read_unlock();
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}
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static unsigned long load_balance_fair(struct lb_env *env)
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static unsigned long task_h_load(struct task_struct *p)
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{
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unsigned long max_load_move = env->max_load_move;
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long rem_load_move = env->max_load_move;
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struct cfs_rq *cfs_rq = task_cfs_rq(p);
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unsigned long load;
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rcu_read_lock();
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update_h_load(cpu_of(env->src_rq));
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load = p->se.load.weight;
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load = div_u64(load * cfs_rq->h_load, cfs_rq->load.weight + 1);
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for_each_leaf_cfs_rq(env->src_rq, env->src_cfs_rq) {
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unsigned long busiest_h_load = env->src_cfs_rq->h_load;
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unsigned long busiest_weight = env->src_cfs_rq->load.weight;
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u64 rem_load, moved_load;
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if (env->flags & (LBF_NEED_BREAK|LBF_ABORT))
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break;
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/*
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* empty group or part of a throttled hierarchy
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*/
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if (!env->src_cfs_rq->task_weight)
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continue;
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if (throttled_lb_pair(env->src_cfs_rq->tg,
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cpu_of(env->src_rq),
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env->dst_cpu))
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continue;
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rem_load = (u64)rem_load_move * busiest_weight;
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rem_load = div_u64(rem_load, busiest_h_load + 1);
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env->max_load_move = rem_load;
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moved_load = balance_tasks(env);
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if (!moved_load)
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continue;
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moved_load *= busiest_h_load;
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moved_load = div_u64(moved_load, busiest_weight + 1);
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rem_load_move -= moved_load;
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if (rem_load_move < 0)
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break;
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}
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rcu_read_unlock();
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return max_load_move - rem_load_move;
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return load;
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}
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#else
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static inline void update_shares(int cpu)
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{
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}
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static unsigned long load_balance_fair(struct lb_env *env)
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static inline void update_h_load(long cpu)
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{
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env->src_cfs_rq = &env->src_rq->cfs;
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return balance_tasks(env);
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}
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static unsigned long task_h_load(struct task_struct *p)
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{
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return p->se.load.weight;
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}
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#endif
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@ -3437,9 +3411,10 @@ static int move_tasks(struct lb_env *env)
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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 = load_balance_fair(env);
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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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@ -4464,6 +4439,7 @@ static int load_balance(int this_cpu, struct rq *this_rq,
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.dst_cpu = this_cpu,
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.dst_rq = this_rq,
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.idle = idle,
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.loop_break = sysctl_sched_nr_migrate,
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};
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cpumask_copy(cpus, cpu_active_mask);
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@ -4504,6 +4480,7 @@ redo:
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env.max_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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local_irq_save(flags);
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double_rq_lock(this_rq, busiest);
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@ -4521,9 +4498,7 @@ redo:
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goto out_balanced;
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if (env.flags & LBF_NEED_BREAK) {
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env.flags += LBF_HAD_BREAK - LBF_NEED_BREAK;
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if (env.flags & LBF_ABORT)
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goto out_balanced;
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env.flags &= ~LBF_NEED_BREAK;
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goto redo;
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}
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@ -5357,7 +5332,6 @@ static void set_curr_task_fair(struct rq *rq)
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void init_cfs_rq(struct cfs_rq *cfs_rq)
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{
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cfs_rq->tasks_timeline = RB_ROOT;
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INIT_LIST_HEAD(&cfs_rq->tasks);
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cfs_rq->min_vruntime = (u64)(-(1LL << 20));
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#ifndef CONFIG_64BIT
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cfs_rq->min_vruntime_copy = cfs_rq->min_vruntime;
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@ -212,9 +212,6 @@ struct cfs_rq {
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struct rb_root tasks_timeline;
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struct rb_node *rb_leftmost;
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struct list_head tasks;
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struct list_head *balance_iterator;
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/*
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* 'curr' points to currently running entity on this cfs_rq.
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* It is set to NULL otherwise (i.e when none are currently running).
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@ -241,11 +238,6 @@ struct cfs_rq {
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struct task_group *tg; /* group that "owns" this runqueue */
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#ifdef CONFIG_SMP
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/*
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* the part of load.weight contributed by tasks
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*/
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unsigned long task_weight;
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/*
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* h_load = weight * f(tg)
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*
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@ -420,6 +412,8 @@ struct rq {
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int cpu;
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int online;
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struct list_head cfs_tasks;
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u64 rt_avg;
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u64 age_stamp;
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u64 idle_stamp;
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