diff options
| -rw-r--r-- | include/linux/sched.h | 8 | ||||
| -rw-r--r-- | kernel/sched.c | 284 |
2 files changed, 225 insertions, 67 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 122a25c1b997..74a1e39e0d3d 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -123,6 +123,7 @@ extern unsigned long nr_running(void); extern unsigned long nr_uninterruptible(void); extern unsigned long nr_active(void); extern unsigned long nr_iowait(void); +extern unsigned long weighted_cpuload(const int cpu); /* @@ -558,9 +559,9 @@ enum idle_type /* * sched-domains (multiprocessor balancing) declarations: */ -#ifdef CONFIG_SMP #define SCHED_LOAD_SCALE 128UL /* increase resolution of load */ +#ifdef CONFIG_SMP #define SD_LOAD_BALANCE 1 /* Do load balancing on this domain. */ #define SD_BALANCE_NEWIDLE 2 /* Balance when about to become idle */ #define SD_BALANCE_EXEC 4 /* Balance on exec */ @@ -713,9 +714,12 @@ struct task_struct { int lock_depth; /* BKL lock depth */ -#if defined(CONFIG_SMP) && defined(__ARCH_WANT_UNLOCKED_CTXSW) +#ifdef CONFIG_SMP +#ifdef __ARCH_WANT_UNLOCKED_CTXSW int oncpu; #endif +#endif + int load_weight; /* for niceness load balancing purposes */ int prio, static_prio; struct list_head run_list; prio_array_t *array; diff --git a/kernel/sched.c b/kernel/sched.c index 678335a8b390..1847a4456a2d 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -168,15 +168,21 @@ */ #define SCALE_PRIO(x, prio) \ - max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO/2), MIN_TIMESLICE) + max(x * (MAX_PRIO - prio) / (MAX_USER_PRIO / 2), MIN_TIMESLICE) -static unsigned int task_timeslice(task_t *p) +static unsigned int static_prio_timeslice(int static_prio) { - if (p->static_prio < NICE_TO_PRIO(0)) - return SCALE_PRIO(DEF_TIMESLICE*4, p->static_prio); + if (static_prio < NICE_TO_PRIO(0)) + return SCALE_PRIO(DEF_TIMESLICE * 4, static_prio); else - return SCALE_PRIO(DEF_TIMESLICE, p->static_prio); + return SCALE_PRIO(DEF_TIMESLICE, static_prio); } + +static inline unsigned int task_timeslice(task_t *p) +{ + return static_prio_timeslice(p->static_prio); +} + #define task_hot(p, now, sd) ((long long) ((now) - (p)->last_ran) \ < (long long) (sd)->cache_hot_time) @@ -207,6 +213,7 @@ struct runqueue { * remote CPUs use both these fields when doing load calculation. */ unsigned long nr_running; + unsigned long raw_weighted_load; #ifdef CONFIG_SMP unsigned long cpu_load[3]; #endif @@ -662,6 +669,68 @@ static int effective_prio(task_t *p) } /* + * To aid in avoiding the subversion of "niceness" due to uneven distribution + * of tasks with abnormal "nice" values across CPUs the contribution that + * each task makes to its run queue's load is weighted according to its + * scheduling class and "nice" value. For SCHED_NORMAL tasks this is just a + * scaled version of the new time slice allocation that they receive on time + * slice expiry etc. + */ + +/* + * Assume: static_prio_timeslice(NICE_TO_PRIO(0)) == DEF_TIMESLICE + * If static_prio_timeslice() is ever changed to break this assumption then + * this code will need modification + */ +#define TIME_SLICE_NICE_ZERO DEF_TIMESLICE +#define LOAD_WEIGHT(lp) \ + (((lp) * SCHED_LOAD_SCALE) / TIME_SLICE_NICE_ZERO) +#define PRIO_TO_LOAD_WEIGHT(prio) \ + LOAD_WEIGHT(static_prio_timeslice(prio)) +#define RTPRIO_TO_LOAD_WEIGHT(rp) \ + (PRIO_TO_LOAD_WEIGHT(MAX_RT_PRIO) + LOAD_WEIGHT(rp)) + +static void set_load_weight(task_t *p) +{ + if (rt_task(p)) { +#ifdef CONFIG_SMP + if (p == task_rq(p)->migration_thread) + /* + * The migration thread does the actual balancing. + * Giving its load any weight will skew balancing + * adversely. + */ + p->load_weight = 0; + else +#endif + p->load_weight = RTPRIO_TO_LOAD_WEIGHT(p->rt_priority); + } else + p->load_weight = PRIO_TO_LOAD_WEIGHT(p->static_prio); +} + +static inline void inc_raw_weighted_load(runqueue_t *rq, const task_t *p) +{ + rq->raw_weighted_load += p->load_weight; +} + +static inline void dec_raw_weighted_load(runqueue_t *rq, const task_t *p) +{ + rq->raw_weighted_load -= p->load_weight; +} + +static inline void inc_nr_running(task_t *p, runqueue_t *rq) +{ + rq->nr_running++; + inc_raw_weighted_load(rq, p); +} + +static inline void dec_nr_running(task_t *p, runqueue_t *rq) +{ + rq->nr_running--; + dec_raw_weighted_load(rq, p); +} + +/* * __activate_task - move a task to the runqueue. */ static void __activate_task(task_t *p, runqueue_t *rq) @@ -671,7 +740,7 @@ static void __activate_task(task_t *p, runqueue_t *rq) if (batch_task(p)) target = rq->expired; enqueue_task(p, target); - rq->nr_running++; + inc_nr_running(p, rq); } /* @@ -680,7 +749,7 @@ static void __activate_task(task_t *p, runqueue_t *rq) static inline void __activate_idle_task(task_t *p, runqueue_t *rq) { enqueue_task_head(p, rq->active); - rq->nr_running++; + inc_nr_running(p, rq); } static int recalc_task_prio(task_t *p, unsigned long long now) @@ -804,7 +873,7 @@ static void activate_task(task_t *p, runqueue_t *rq, int local) */ static void deactivate_task(struct task_struct *p, runqueue_t *rq) { - rq->nr_running--; + dec_nr_running(p, rq); dequeue_task(p, p->array); p->array = NULL; } @@ -859,6 +928,12 @@ inline int task_curr(const task_t *p) return cpu_curr(task_cpu(p)) == p; } +/* Used instead of source_load when we know the type == 0 */ +unsigned long weighted_cpuload(const int cpu) +{ + return cpu_rq(cpu)->raw_weighted_load; +} + #ifdef CONFIG_SMP typedef struct { struct list_head list; @@ -948,7 +1023,8 @@ void kick_process(task_t *p) } /* - * Return a low guess at the load of a migration-source cpu. + * Return a low guess at the load of a migration-source cpu weighted + * according to the scheduling class and "nice" value. * * We want to under-estimate the load of migration sources, to * balance conservatively. @@ -956,24 +1032,36 @@ void kick_process(task_t *p) static inline unsigned long source_load(int cpu, int type) { runqueue_t *rq = cpu_rq(cpu); - unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE; + if (type == 0) - return load_now; + return rq->raw_weighted_load; - return min(rq->cpu_load[type-1], load_now); + return min(rq->cpu_load[type-1], rq->raw_weighted_load); } /* - * Return a high guess at the load of a migration-target cpu + * Return a high guess at the load of a migration-target cpu weighted + * according to the scheduling class and "nice" value. */ static inline unsigned long target_load(int cpu, int type) { runqueue_t *rq = cpu_rq(cpu); - unsigned long load_now = rq->nr_running * SCHED_LOAD_SCALE; + if (type == 0) - return load_now; + return rq->raw_weighted_load; - return max(rq->cpu_load[type-1], load_now); + return max(rq->cpu_load[type-1], rq->raw_weighted_load); +} + +/* + * Return the average load per task on the cpu's run queue + */ +static inline unsigned long cpu_avg_load_per_task(int cpu) +{ + runqueue_t *rq = cpu_rq(cpu); + unsigned long n = rq->nr_running; + + return n ? rq->raw_weighted_load / n : SCHED_LOAD_SCALE; } /* @@ -1046,7 +1134,7 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) cpus_and(tmp, group->cpumask, p->cpus_allowed); for_each_cpu_mask(i, tmp) { - load = source_load(i, 0); + load = weighted_cpuload(i); if (load < min_load || (load == min_load && i == this_cpu)) { min_load = load; @@ -1226,17 +1314,19 @@ static int try_to_wake_up(task_t *p, unsigned int state, int sync) if (this_sd->flags & SD_WAKE_AFFINE) { unsigned long tl = this_load; + unsigned long tl_per_task = cpu_avg_load_per_task(this_cpu); + /* * If sync wakeup then subtract the (maximum possible) * effect of the currently running task from the load * of the current CPU: */ if (sync) - tl -= SCHED_LOAD_SCALE; + tl -= current->load_weight; if ((tl <= load && - tl + target_load(cpu, idx) <= SCHED_LOAD_SCALE) || - 100*(tl + SCHED_LOAD_SCALE) <= imbalance*load) { + tl + target_load(cpu, idx) <= tl_per_task) || + 100*(tl + p->load_weight) <= imbalance*load) { /* * This domain has SD_WAKE_AFFINE and * p is cache cold in this domain, and @@ -1435,7 +1525,7 @@ void fastcall wake_up_new_task(task_t *p, unsigned long clone_flags) list_add_tail(&p->run_list, ¤t->run_list); p->array = current->array; p->array->nr_active++; - rq->nr_running++; + inc_nr_running(p, rq); } set_need_resched(); } else @@ -1802,9 +1892,9 @@ void pull_task(runqueue_t *src_rq, prio_array_t *src_array, task_t *p, runqueue_t *this_rq, prio_array_t *this_array, int this_cpu) { dequeue_task(p, src_array); - src_rq->nr_running--; + dec_nr_running(p, src_rq); set_task_cpu(p, this_cpu); - this_rq->nr_running++; + inc_nr_running(p, this_rq); enqueue_task(p, this_array); p->timestamp = (p->timestamp - src_rq->timestamp_last_tick) + this_rq->timestamp_last_tick; @@ -1852,24 +1942,27 @@ int can_migrate_task(task_t *p, runqueue_t *rq, int this_cpu, } /* - * move_tasks tries to move up to max_nr_move tasks from busiest to this_rq, - * as part of a balancing operation within "domain". Returns the number of - * tasks moved. + * move_tasks tries to move up to max_nr_move tasks and max_load_move weighted + * load from busiest to this_rq, as part of a balancing operation within + * "domain". Returns the number of tasks moved. * * Called with both runqueues locked. */ static int move_tasks(runqueue_t *this_rq, int this_cpu, runqueue_t *busiest, - unsigned long max_nr_move, struct sched_domain *sd, - enum idle_type idle, int *all_pinned) + unsigned long max_nr_move, unsigned long max_load_move, + struct sched_domain *sd, enum idle_type idle, + int *all_pinned) { prio_array_t *array, *dst_array; struct list_head *head, *curr; int idx, pulled = 0, pinned = 0; + long rem_load_move; task_t *tmp; - if (max_nr_move == 0) + if (max_nr_move == 0 || max_load_move == 0) goto out; + rem_load_move = max_load_move; pinned = 1; /* @@ -1910,7 +2003,8 @@ skip_queue: curr = curr->prev; - if (!can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) { + if (tmp->load_weight > rem_load_move || + !can_migrate_task(tmp, busiest, this_cpu, sd, idle, &pinned)) { if (curr != head) goto skip_queue; idx++; @@ -1924,9 +2018,13 @@ skip_queue: pull_task(busiest, array, tmp, this_rq, dst_array, this_cpu); pulled++; + rem_load_move -= tmp->load_weight; - /* We only want to steal up to the prescribed number of tasks. */ - if (pulled < max_nr_move) { + /* + * We only want to steal up to the prescribed number of tasks + * and the prescribed amount of weighted load. + */ + if (pulled < max_nr_move && rem_load_move > 0) { if (curr != head) goto skip_queue; idx++; @@ -1947,7 +2045,7 @@ out: /* * find_busiest_group finds and returns the busiest CPU group within the - * domain. It calculates and returns the number of tasks which should be + * domain. It calculates and returns the amount of weighted load which should be * moved to restore balance via the imbalance parameter. */ static struct sched_group * @@ -1957,9 +2055,13 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, struct sched_group *busiest = NULL, *this = NULL, *group = sd->groups; unsigned long max_load, avg_load, total_load, this_load, total_pwr; unsigned long max_pull; + unsigned long busiest_load_per_task, busiest_nr_running; + unsigned long this_load_per_task, this_nr_running; int load_idx; max_load = this_load = total_load = total_pwr = 0; + busiest_load_per_task = busiest_nr_running = 0; + this_load_per_task = this_nr_running = 0; if (idle == NOT_IDLE) load_idx = sd->busy_idx; else if (idle == NEWLY_IDLE) @@ -1971,13 +2073,16 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, unsigned long load; int local_group; int i; + unsigned long sum_nr_running, sum_weighted_load; local_group = cpu_isset(this_cpu, group->cpumask); /* Tally up the load of all CPUs in the group */ - avg_load = 0; + sum_weighted_load = sum_nr_running = avg_load = 0; for_each_cpu_mask(i, group->cpumask) { + runqueue_t *rq = cpu_rq(i); + if (*sd_idle && !idle_cpu(i)) *sd_idle = 0; @@ -1988,6 +2093,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, load = source_load(i, load_idx); avg_load += load; + sum_nr_running += rq->nr_running; + sum_weighted_load += rq->raw_weighted_load; } total_load += avg_load; @@ -1999,14 +2106,19 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, if (local_group) { this_load = avg_load; this = group; - } else if (avg_load > max_load) { + this_nr_running = sum_nr_running; + this_load_per_task = sum_weighted_load; + } else if (avg_load > max_load && + sum_nr_running > group->cpu_power / SCHED_LOAD_SCALE) { max_load = avg_load; busiest = group; + busiest_nr_running = sum_nr_running; + busiest_load_per_task = sum_weighted_load; } group = group->next; } while (group != sd->groups); - if (!busiest || this_load >= max_load || max_load <= SCHED_LOAD_SCALE) + if (!busiest || this_load >= max_load || busiest_nr_running == 0) goto out_balanced; avg_load = (SCHED_LOAD_SCALE * total_load) / total_pwr; @@ -2015,6 +2127,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, 100*max_load <= sd->imbalance_pct*this_load) goto out_balanced; + busiest_load_per_task /= busiest_nr_running; /* * We're trying to get all the cpus to the average_load, so we don't * want to push ourselves above the average load, nor do we wish to @@ -2026,21 +2139,50 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, * by pulling tasks to us. Be careful of negative numbers as they'll * appear as very large values with unsigned longs. */ + if (max_load <= busiest_load_per_task) + goto out_balanced; + + /* + * In the presence of smp nice balancing, certain scenarios can have + * max load less than avg load(as we skip the groups at or below + * its cpu_power, while calculating max_load..) + */ + if (max_load < avg_load) { + *imbalance = 0; + goto small_imbalance; + } /* Don't want to pull so many tasks that a group would go idle */ - max_pull = min(max_load - avg_load, max_load - SCHED_LOAD_SCALE); + max_pull = min(max_load - avg_load, max_load - busiest_load_per_task); /* How much load to actually move to equalise the imbalance */ *imbalance = min(max_pull * busiest->cpu_power, (avg_load - this_load) * this->cpu_power) / SCHED_LOAD_SCALE; - if (*imbalance < SCHED_LOAD_SCALE) { - unsigned long pwr_now = 0, pwr_move = 0; + /* + * if *imbalance is less than the average load per runnable task + * there is no gaurantee that any tasks will be moved so we'll have + * a think about bumping its value to force at least one task to be + * moved + */ + if (*imbalance < busiest_load_per_task) { + unsigned long pwr_now, pwr_move; unsigned long tmp; + unsigned int imbn; + +small_imbalance: + pwr_move = pwr_now = 0; + imbn = 2; + if (this_nr_running) { + this_load_per_task /= this_nr_running; + if (busiest_load_per_task > this_load_per_task) + imbn = 1; + } else + this_load_per_task = SCHED_LOAD_SCALE; - if (max_load - this_load >= SCHED_LOAD_SCALE*2) { - *imbalance = 1; + if (max_load - this_load >= busiest_load_per_task * imbn) { + *imbalance = busiest_load_per_task; return busiest; } @@ -2050,35 +2192,34 @@ find_busiest_group(struct sched_domain *sd, int this_cpu, * moving them. */ - pwr_now += busiest->cpu_power*min(SCHED_LOAD_SCALE, max_load); - pwr_now += this->cpu_power*min(SCHED_LOAD_SCALE, this_load); + pwr_now += busiest->cpu_power * + min(busiest_load_per_task, max_load); + pwr_now += this->cpu_power * + min(this_load_per_task, this_load); pwr_now /= SCHED_LOAD_SCALE; /* Amount of load we'd subtract */ - tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/busiest->cpu_power; + tmp = busiest_load_per_task*SCHED_LOAD_SCALE/busiest->cpu_power; if (max_load > tmp) - pwr_move += busiest->cpu_power*min(SCHED_LOAD_SCALE, - max_load - tmp); + pwr_move += busiest->cpu_power * + min(busiest_load_per_task, max_load - tmp); /* Amount of load we'd add */ if (max_load*busiest->cpu_power < - SCHED_LOAD_SCALE*SCHED_LOAD_SCALE) + busiest_load_per_task*SCHED_LOAD_SCALE) tmp = max_load*busiest->cpu_power/this->cpu_power; else - tmp = SCHED_LOAD_SCALE*SCHED_LOAD_SCALE/this->cpu_power; - pwr_move += this->cpu_power*min(SCHED_LOAD_SCALE, this_load + tmp); + tmp = busiest_load_per_task*SCHED_LOAD_SCALE/this->cpu_power; + pwr_move += this->cpu_power*min(this_load_per_task, this_load + tmp); pwr_move /= SCHED_LOAD_SCALE; /* Move if we gain throughput */ if (pwr_move <= pwr_now) goto out_balanced; - *imbalance = 1; - return busiest; + *imbalance = busiest_load_per_task; } - /* Get rid of the scaling factor, rounding down as we divide */ - *imbalance = *imbalance / SCHED_LOAD_SCALE; return busiest; out_balanced: @@ -2091,18 +2232,21 @@ out_balanced: * find_busiest_queue - find the busiest runqueue among the cpus in group. */ static runqueue_t *find_busiest_queue(struct sched_group *group, - enum idle_type idle) + enum idle_type idle, unsigned long imbalance) { - unsigned long load, max_load = 0; - runqueue_t *busiest = NULL; + unsigned long max_load = 0; + runqueue_t *busiest = NULL, *rqi; int i; for_each_cpu_mask(i, group->cpumask) { - load = source_load(i, 0); + rqi = cpu_rq(i); + + if (rqi->nr_running == 1 && rqi->raw_weighted_load > imbalance) + continue; - if (load > max_load) { - max_load = load; - busiest = cpu_rq(i); + if (rqi->raw_weighted_load > max_load) { + max_load = rqi->raw_weighted_load; + busiest = rqi; } } @@ -2115,6 +2259,7 @@ static runqueue_t *find_busiest_queue(struct sched_group *group, */ #define MAX_PINNED_INTERVAL 512 +#define minus_1_or_zero(n) ((n) > 0 ? (n) - 1 : 0) /* * Check this_cpu to ensure it is balanced within domain. Attempt to move * tasks if there is an imbalance. @@ -2142,7 +2287,7 @@ static int load_balance(int this_cpu, runqueue_t *this_rq, goto out_balanced; } - busiest = find_busiest_queue(group, idle); + busiest = find_busiest_queue(group, idle, imbalance); if (!busiest) { schedstat_inc(sd, lb_nobusyq[idle]); goto out_balanced; @@ -2162,6 +2307,7 @@ static int load_balance(int this_cpu, runqueue_t *this_rq, */ double_rq_lock(this_rq, busiest); nr_moved = move_tasks(this_rq, this_cpu, busiest, + minus_1_or_zero(busiest->nr_running), imbalance, sd, idle, &all_pinned); double_rq_unlock(this_rq, busiest); @@ -2265,7 +2411,7 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq, goto out_balanced; } - busiest = find_busiest_queue(group, NEWLY_IDLE); + busiest = find_busiest_queue(group, NEWLY_IDLE, imbalance); if (!busiest) { schedstat_inc(sd, lb_nobusyq[NEWLY_IDLE]); goto out_balanced; @@ -2280,6 +2426,7 @@ static int load_balance_newidle(int this_cpu, runqueue_t *this_rq, /* Attempt to move tasks */ double_lock_balance(this_rq, busiest); nr_moved = move_tasks(this_rq, this_cpu, busiest, + minus_1_or_zero(busiest->nr_running), imbalance, sd, NEWLY_IDLE, NULL); spin_unlock(&busiest->lock); } @@ -2361,7 +2508,8 @@ static void active_load_balance(runqueue_t *busiest_rq, int busiest_cpu) schedstat_inc(sd, alb_cnt); - if (move_tasks(target_rq, target_cpu, busiest_rq, 1, sd, SCHED_IDLE, NULL)) + if (move_tasks(target_rq, target_cpu, busiest_rq, 1, + RTPRIO_TO_LOAD_WEIGHT(100), sd, SCHED_IDLE, NULL)) schedstat_inc(sd, alb_pushed); else schedstat_inc(sd, alb_failed); @@ -2389,7 +2537,7 @@ static void rebalance_tick(int this_cpu, runqueue_t *this_rq, struct sched_domain *sd; int i; - this_load = this_rq->nr_running * SCHED_LOAD_SCALE; + this_load = this_rq->raw_weighted_load; /* Update our load */ for (i = 0; i < 3; i++) { unsigned long new_load = this_load; @@ -3441,17 +3589,21 @@ void set_user_nice(task_t *p, long nice) goto out_unlock; } array = p->array; - if (array) + if (array) { dequeue_task(p, array); + dec_raw_weighted_load(rq, p); + } old_prio = p->prio; new_prio = NICE_TO_PRIO(nice); delta = new_prio - old_prio; p->static_prio = NICE_TO_PRIO(nice); + set_load_weight(p); p->prio += delta; if (array) { enqueue_task(p, array); + inc_raw_weighted_load(rq, p); /* * If the task increased its priority or is running and * lowered its priority, then reschedule its CPU: @@ -3587,6 +3739,7 @@ static void __setscheduler(struct task_struct *p, int policy, int prio) if (policy == SCHED_BATCH) p->sleep_avg = 0; } + set_load_weight(p); } /** @@ -6106,6 +6259,7 @@ void __init sched_init(void) } } + set_load_weight(&init_task); /* * The boot idle thread does lazy MMU switching as well: */ |