From 62fb185130e4d420f71a30ff59d8b16b74ef5d2b Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 25 Feb 2008 17:34:02 +0100 Subject: sched: revert load_balance_monitor() changes The following commits cause a number of regressions: commit 58e2d4ca581167c2a079f4ee02be2f0bc52e8729 Author: Srivatsa Vaddagiri Date: Fri Jan 25 21:08:00 2008 +0100 sched: group scheduling, change how cpu load is calculated commit 6b2d7700266b9402e12824e11e0099ae6a4a6a79 Author: Srivatsa Vaddagiri Date: Fri Jan 25 21:08:00 2008 +0100 sched: group scheduler, fix fairness of cpu bandwidth allocation for task groups Namely: - very frequent wakeups on SMP, reported by PowerTop users. - cacheline trashing on (large) SMP - some latencies larger than 500ms While there is a mergeable patch to fix the latter, the former issues are not fixable in a manner suitable for .25 (we're at -rc3 now). Hence we revert them and try again in v2.6.26. Signed-off-by: Peter Zijlstra CC: Srivatsa Vaddagiri Tested-by: Alexey Zaytsev Signed-off-by: Ingo Molnar --- kernel/sched_fair.c | 115 ++++++++++++++++------------------------------------ 1 file changed, 35 insertions(+), 80 deletions(-) (limited to 'kernel/sched_fair.c') diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index c8e6492c592..3df4d46994c 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; } -- cgit v1.2.3