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sched: Pre-compute cpumask_weight(sched_domain_span(sd))

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Dave reported that his large SPARC machines spend lots of time in
hweight64(), try and optimize some of those needless cpumask_weight()
invocations (esp. with the large offstack cpumasks these are very
expensive indeed).

Reported-by: David Miller <davem@davemloft.net>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2010-04-16 14:59:29 +02:00 committed by Ingo Molnar
parent 74f5187ac8
commit 669c55e9f9
3 changed files with 9 additions and 7 deletions
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1
include/linux/sched.h
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@ -960,6 +960,7 @@ struct sched_domain {
char *name;
#endif
unsigned int span_weight;
/*
* Span of all CPUs in this domain.
*

3
kernel/sched.c
View file

@ -6271,6 +6271,9 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
struct rq *rq = cpu_rq(cpu);
struct sched_domain *tmp;
for (tmp = sd; tmp; tmp = tmp->parent)
tmp->span_weight = cpumask_weight(sched_domain_span(tmp));
/* Remove the sched domains which do not contribute to scheduling. */
for (tmp = sd; tmp; ) {
struct sched_domain *parent = tmp->parent;

12
kernel/sched_fair.c
View file

@ -1508,9 +1508,7 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
* Pick the largest domain to update shares over
*/
tmp = sd;
if (affine_sd && (!tmp ||
cpumask_weight(sched_domain_span(affine_sd)) >
cpumask_weight(sched_domain_span(sd))))
if (affine_sd && (!tmp || affine_sd->span_weight > sd->span_weight))
tmp = affine_sd;
if (tmp) {
@ -1554,10 +1552,10 @@ select_task_rq_fair(struct rq *rq, struct task_struct *p, int sd_flag, int wake_
/* Now try balancing at a lower domain level of new_cpu */
cpu = new_cpu;
weight = cpumask_weight(sched_domain_span(sd));
weight = sd->span_weight;
sd = NULL;
for_each_domain(cpu, tmp) {
if (weight <= cpumask_weight(sched_domain_span(tmp)))
if (weight <= tmp->span_weight)
break;
if (tmp->flags & sd_flag)
sd = tmp;
@ -2243,7 +2241,7 @@ unsigned long __weak arch_scale_freq_power(struct sched_domain *sd, int cpu)
unsigned long default_scale_smt_power(struct sched_domain *sd, int cpu)
{
unsigned long weight = cpumask_weight(sched_domain_span(sd));
unsigned long weight = sd->span_weight;
unsigned long smt_gain = sd->smt_gain;
smt_gain /= weight;
@ -2276,7 +2274,7 @@ unsigned long scale_rt_power(int cpu)
static void update_cpu_power(struct sched_domain *sd, int cpu)
{
unsigned long weight = cpumask_weight(sched_domain_span(sd));
unsigned long weight = sd->span_weight;
unsigned long power = SCHED_LOAD_SCALE;
struct sched_group *sdg = sd->groups;