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[PATCH] sched: balance timers

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Do CPU load averaging over a number of different intervals.  Allow each
interval to be chosen by sending a parameter to source_load and target_load.
0 is instantaneous, idx > 0 returns a decaying average with the most recent
sample weighted at 2^(idx-1).  To a maximum of 3 (could be easily increased).

So generally a higher number will result in more conservative balancing.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Nick Piggin 2005-06-25 14:57:13 -07:00 committed by Linus Torvalds
parent 99b61ccf0b
commit 7897986bad
5 changed files with 98 additions and 68 deletions
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4
include/asm-i386/topology.h
View File

@ -74,6 +74,10 @@ static inline int node_to_first_cpu(int node)
.imbalance_pct = 125, \
.cache_hot_time = (10*1000000), \
.cache_nice_tries = 1, \
.busy_idx = 3, \
.idle_idx = 1, \
.newidle_idx = 2, \
.wake_idx = 1, \
.per_cpu_gain = 100, \
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_EXEC \

6
include/asm-x86_64/topology.h
View File

@ -39,7 +39,11 @@ extern int __node_distance(int, int);
.busy_factor = 32, \
.imbalance_pct = 125, \
.cache_hot_time = (10*1000000), \
.cache_nice_tries = 1, \
.cache_nice_tries = 2, \
.busy_idx = 3, \
.idle_idx = 2, \
.newidle_idx = 1, \
.wake_idx = 1, \
.per_cpu_gain = 100, \
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_NEWIDLE \

4
include/linux/sched.h
View File

@ -488,6 +488,10 @@ struct sched_domain {
unsigned long long cache_hot_time; /* Task considered cache hot (ns) */
unsigned int cache_nice_tries; /* Leave cache hot tasks for # tries */
unsigned int per_cpu_gain; /* CPU % gained by adding domain cpus */
unsigned int busy_idx;
unsigned int idle_idx;
unsigned int newidle_idx;
unsigned int wake_idx;
int flags; /* See SD_* */
/* Runtime fields. */

8
include/linux/topology.h
View File

@ -89,6 +89,10 @@
.cache_hot_time = 0, \
.cache_nice_tries = 0, \
.per_cpu_gain = 25, \
.busy_idx = 0, \
.idle_idx = 0, \
.newidle_idx = 0, \
.wake_idx = 0, \
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_NEWIDLE \
| SD_BALANCE_EXEC \
@ -115,6 +119,10 @@
.cache_hot_time = (5*1000000/2), \
.cache_nice_tries = 1, \
.per_cpu_gain = 100, \
.busy_idx = 2, \
.idle_idx = 0, \
.newidle_idx = 1, \
.wake_idx = 1, \
.flags = SD_LOAD_BALANCE \
| SD_BALANCE_NEWIDLE \
| SD_BALANCE_EXEC \

144
kernel/sched.c
View File

@ -206,7 +206,7 @@ struct runqueue {
*/
unsigned long nr_running;
#ifdef CONFIG_SMP
unsigned long cpu_load;
unsigned long cpu_load[3];
#endif
unsigned long long nr_switches;
@ -886,23 +886,27 @@ void kick_process(task_t *p)
* We want to under-estimate the load of migration sources, to
* balance conservatively.
*/
static inline unsigned long source_load(int cpu)
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 min(rq->cpu_load, load_now);
return min(rq->cpu_load[type-1], load_now);
}
/*
* Return a high guess at the load of a migration-target cpu
*/
static inline unsigned long target_load(int cpu)
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 max(rq->cpu_load, load_now);
return max(rq->cpu_load[type-1], load_now);
}
#endif
@ -967,7 +971,7 @@ static int try_to_wake_up(task_t * p, unsigned int state, int sync)
runqueue_t *rq;
#ifdef CONFIG_SMP
unsigned long load, this_load;
struct sched_domain *sd;
struct sched_domain *sd, *this_sd = NULL;
int new_cpu;
#endif
@ -986,72 +990,64 @@ static int try_to_wake_up(task_t * p, unsigned int state, int sync)
if (unlikely(task_running(rq, p)))
goto out_activate;
#ifdef CONFIG_SCHEDSTATS
new_cpu = cpu;
schedstat_inc(rq, ttwu_cnt);
if (cpu == this_cpu) {
schedstat_inc(rq, ttwu_local);
} else {
for_each_domain(this_cpu, sd) {
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_remote);
break;
}
goto out_set_cpu;
}
for_each_domain(this_cpu, sd) {
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_wake_remote);
this_sd = sd;
break;
}
}
#endif
new_cpu = cpu;
if (cpu == this_cpu || unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
if (unlikely(!cpu_isset(this_cpu, p->cpus_allowed)))
goto out_set_cpu;
load = source_load(cpu);
this_load = target_load(this_cpu);
/*
* If sync wakeup then subtract the (maximum possible) effect of
* the currently running task from the load of the current CPU:
* Check for affine wakeup and passive balancing possibilities.
*/
if (sync)
this_load -= SCHED_LOAD_SCALE;
/* Don't pull the task off an idle CPU to a busy one */
if (load < SCHED_LOAD_SCALE/2 && this_load > SCHED_LOAD_SCALE/2)
goto out_set_cpu;
new_cpu = this_cpu; /* Wake to this CPU if we can */
/*
* Scan domains for affine wakeup and passive balancing
* possibilities.
*/
for_each_domain(this_cpu, sd) {
if (this_sd) {
int idx = this_sd->wake_idx;
unsigned int imbalance;
/*
* Start passive balancing when half the imbalance_pct
* limit is reached.
*/
imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;
if ((sd->flags & SD_WAKE_AFFINE) &&
!task_hot(p, rq->timestamp_last_tick, sd)) {
load = source_load(cpu, idx);
this_load = target_load(this_cpu, idx);
/*
* If sync wakeup then subtract the (maximum possible) effect of
* the currently running task from the load of the current CPU:
*/
if (sync)
this_load -= SCHED_LOAD_SCALE;
/* Don't pull the task off an idle CPU to a busy one */
if (load < SCHED_LOAD_SCALE/2 && this_load > SCHED_LOAD_SCALE/2)
goto out_set_cpu;
new_cpu = this_cpu; /* Wake to this CPU if we can */
if ((this_sd->flags & SD_WAKE_AFFINE) &&
!task_hot(p, rq->timestamp_last_tick, this_sd)) {
/*
* This domain has SD_WAKE_AFFINE and p is cache cold
* in this domain.
*/
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_move_affine);
goto out_set_cpu;
}
} else if ((sd->flags & SD_WAKE_BALANCE) &&
schedstat_inc(this_sd, ttwu_move_affine);
goto out_set_cpu;
} else if ((this_sd->flags & SD_WAKE_BALANCE) &&
imbalance*this_load <= 100*load) {
/*
* This domain has SD_WAKE_BALANCE and there is
* an imbalance.
*/
if (cpu_isset(cpu, sd->span)) {
schedstat_inc(sd, ttwu_move_balance);
goto out_set_cpu;
}
schedstat_inc(this_sd, ttwu_move_balance);
goto out_set_cpu;
}
}
@ -1509,7 +1505,7 @@ static int find_idlest_cpu(struct task_struct *p, int this_cpu,
cpus_and(mask, sd->span, p->cpus_allowed);
for_each_cpu_mask(i, mask) {
load = target_load(i);
load = target_load(i, sd->wake_idx);
if (load < min_load) {
min_cpu = i;
@ -1522,7 +1518,7 @@ static int find_idlest_cpu(struct task_struct *p, int this_cpu,
}
/* add +1 to account for the new task */
this_load = source_load(this_cpu) + SCHED_LOAD_SCALE;
this_load = source_load(this_cpu, sd->wake_idx) + SCHED_LOAD_SCALE;
/*
* Would with the addition of the new task to the
@ -1767,8 +1763,15 @@ 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;
int load_idx;
max_load = this_load = total_load = total_pwr = 0;
if (idle == NOT_IDLE)
load_idx = sd->busy_idx;
else if (idle == NEWLY_IDLE)
load_idx = sd->newidle_idx;
else
load_idx = sd->idle_idx;
do {
unsigned long load;
@ -1783,9 +1786,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
for_each_cpu_mask(i, group->cpumask) {
/* Bias balancing toward cpus of our domain */
if (local_group)
load = target_load(i);
load = target_load(i, load_idx);
else
load = source_load(i);
load = source_load(i, load_idx);
avg_load += load;
}
@ -1895,7 +1898,7 @@ static runqueue_t *find_busiest_queue(struct sched_group *group)
int i;
for_each_cpu_mask(i, group->cpumask) {
load = source_load(i);
load = source_load(i, 0);
if (load > max_load) {
max_load = load;
@ -2150,18 +2153,23 @@ static void rebalance_tick(int this_cpu, runqueue_t *this_rq,
unsigned long old_load, this_load;
unsigned long j = jiffies + CPU_OFFSET(this_cpu);
struct sched_domain *sd;
int i;
/* Update our load */
old_load = this_rq->cpu_load;
this_load = this_rq->nr_running * SCHED_LOAD_SCALE;
/*
* Round up the averaging division if load is increasing. This
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
if (this_load > old_load)
old_load++;
this_rq->cpu_load = (old_load + this_load) / 2;
/* Update our load */
for (i = 0; i < 3; i++) {
unsigned long new_load = this_load;
int scale = 1 << i;
old_load = this_rq->cpu_load[i];
/*
* Round up the averaging division if load is increasing. This
* prevents us from getting stuck on 9 if the load is 10, for
* example.
*/
if (new_load > old_load)
new_load += scale-1;
this_rq->cpu_load[i] = (old_load*(scale-1) + new_load) / scale;
}
for_each_domain(this_cpu, sd) {
unsigned long interval;
@ -4921,13 +4929,15 @@ void __init sched_init(void)
rq = cpu_rq(i);
spin_lock_init(&rq->lock);
rq->nr_running = 0;
rq->active = rq->arrays;
rq->expired = rq->arrays + 1;
rq->best_expired_prio = MAX_PRIO;
#ifdef CONFIG_SMP
rq->sd = &sched_domain_dummy;
rq->cpu_load = 0;
for (j = 1; j < 3; j++)
rq->cpu_load[j] = 0;
rq->active_balance = 0;
rq->push_cpu = 0;
rq->migration_thread = NULL;