[PATCH 8/13] generalised CPU load averaging
From: Nick Piggin
Date: Thu Feb 24 2005 - 02:38:33 EST
8/13
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@xxxxxxxxxxxx>
Index: linux-2.6/include/asm-i386/topology.h
===================================================================
--- linux-2.6.orig/include/asm-i386/topology.h 2005-02-24 17:31:22.664322588 +1100
+++ linux-2.6/include/asm-i386/topology.h 2005-02-24 17:43:37.733579601 +1100
@@ -77,6 +77,10 @@
.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 \
Index: linux-2.6/include/asm-x86_64/topology.h
===================================================================
--- linux-2.6.orig/include/asm-x86_64/topology.h 2005-02-24 17:31:22.664322588 +1100
+++ linux-2.6/include/asm-x86_64/topology.h 2005-02-24 17:43:37.733579601 +1100
@@ -49,7 +49,11 @@
.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 \
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h 2005-02-24 17:31:28.428610071 +1100
+++ linux-2.6/include/linux/sched.h 2005-02-24 17:43:37.503607973 +1100
@@ -451,6 +451,10 @@
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. */
Index: linux-2.6/include/linux/topology.h
===================================================================
--- linux-2.6.orig/include/linux/topology.h 2005-02-24 17:31:22.665322464 +1100
+++ linux-2.6/include/linux/topology.h 2005-02-24 17:43:37.733579601 +1100
@@ -86,6 +86,10 @@
.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 \
@@ -112,6 +116,10 @@
.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 \
Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c 2005-02-24 17:39:06.530045151 +1100
+++ linux-2.6/kernel/sched.c 2005-02-24 17:43:37.913557397 +1100
@@ -204,7 +204,7 @@
*/
unsigned long nr_running;
#ifdef CONFIG_SMP
- unsigned long cpu_load;
+ unsigned long cpu_load[3];
#endif
unsigned long long nr_switches;
@@ -884,23 +884,27 @@
* 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
@@ -965,7 +969,7 @@
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
@@ -984,72 +988,64 @@
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;
+ if (this_sd) {
+ int idx = this_sd->wake_idx;
+ unsigned int imbalance;
- new_cpu = this_cpu; /* Wake to this CPU if we can */
+ load = source_load(cpu, idx);
+ this_load = target_load(this_cpu, idx);
- /*
- * Scan domains for affine wakeup and passive balancing
- * possibilities.
- */
- for_each_domain(this_cpu, sd) {
- unsigned int imbalance;
/*
- * Start passive balancing when half the imbalance_pct
- * limit is reached.
+ * If sync wakeup then subtract the (maximum possible) effect of
+ * the currently running task from the load of the current CPU:
*/
- imbalance = sd->imbalance_pct + (sd->imbalance_pct - 100) / 2;
+ if (sync)
+ this_load -= SCHED_LOAD_SCALE;
- if ((sd->flags & SD_WAKE_AFFINE) &&
- !task_hot(p, rq->timestamp_last_tick, sd)) {
+ /* 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;
}
}
@@ -1507,7 +1503,7 @@
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;
@@ -1520,7 +1516,7 @@
}
/* 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
@@ -1765,8 +1761,15 @@
{
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;
@@ -1781,9 +1784,9 @@
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;
}
@@ -1893,7 +1896,7 @@
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;
@@ -2165,18 +2168,23 @@
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;
@@ -4958,13 +4966,15 @@
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;