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authorPreeti U Murthy <preeti@linux.vnet.ibm.com>2013-10-30 08:42:52 +0530
committerIngo Molnar <mingo@kernel.org>2013-11-06 12:37:55 +0100
commit37dc6b50cee97954c4e6edcd5b1fa614b76038ee (patch)
treef317a2532d134b113c088bdf5026fb4aef1423c4
parent2042abe7977222ef606306faa2dce8fd51e98e65 (diff)
downloadblackbird-op-linux-37dc6b50cee97954c4e6edcd5b1fa614b76038ee.tar.gz
blackbird-op-linux-37dc6b50cee97954c4e6edcd5b1fa614b76038ee.zip
sched: Remove unnecessary iteration over sched domains to update nr_busy_cpus
nr_busy_cpus parameter is used by nohz_kick_needed() to find out the number of busy cpus in a sched domain which has SD_SHARE_PKG_RESOURCES flag set. Therefore instead of updating nr_busy_cpus at every level of sched domain, since it is irrelevant, we can update this parameter only at the parent domain of the sd which has this flag set. Introduce a per-cpu parameter sd_busy which represents this parent domain. In nohz_kick_needed() we directly query the nr_busy_cpus parameter associated with the groups of sd_busy. By associating sd_busy with the highest domain which has SD_SHARE_PKG_RESOURCES flag set, we cover all lower level domains which could have this flag set and trigger nohz_idle_balancing if any of the levels have more than one busy cpu. sd_busy is irrelevant for asymmetric load balancing. However sd_asym has been introduced to represent the highest sched domain which has SD_ASYM_PACKING flag set so that it can be queried directly when required. While we are at it, we might as well change the nohz_idle parameter to be updated at the sd_busy domain level alone and not the base domain level of a CPU. This will unify the concept of busy cpus at just one level of sched domain where it is currently used. Signed-off-by: Preeti U Murthy<preeti@linux.vnet.ibm.com> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: svaidy@linux.vnet.ibm.com Cc: vincent.guittot@linaro.org Cc: bitbucket@online.de Cc: benh@kernel.crashing.org Cc: anton@samba.org Cc: Morten.Rasmussen@arm.com Cc: pjt@google.com Cc: peterz@infradead.org Cc: mikey@neuling.org Link: http://lkml.kernel.org/r/20131030031252.23426.4417.stgit@preeti.in.ibm.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
-rw-r--r--kernel/sched/core.c6
-rw-r--r--kernel/sched/fair.c38
-rw-r--r--kernel/sched/sched.h2
3 files changed, 28 insertions, 18 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index aa066f306be2..1deccd78be98 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -4883,6 +4883,8 @@ DEFINE_PER_CPU(struct sched_domain *, sd_llc);
DEFINE_PER_CPU(int, sd_llc_size);
DEFINE_PER_CPU(int, sd_llc_id);
DEFINE_PER_CPU(struct sched_domain *, sd_numa);
+DEFINE_PER_CPU(struct sched_domain *, sd_busy);
+DEFINE_PER_CPU(struct sched_domain *, sd_asym);
static void update_top_cache_domain(int cpu)
{
@@ -4894,6 +4896,7 @@ static void update_top_cache_domain(int cpu)
if (sd) {
id = cpumask_first(sched_domain_span(sd));
size = cpumask_weight(sched_domain_span(sd));
+ rcu_assign_pointer(per_cpu(sd_busy, cpu), sd->parent);
}
rcu_assign_pointer(per_cpu(sd_llc, cpu), sd);
@@ -4902,6 +4905,9 @@ static void update_top_cache_domain(int cpu)
sd = lowest_flag_domain(cpu, SD_NUMA);
rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);
+
+ sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
+ rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
}
/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 074551a792f7..df77c605c7a6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6534,16 +6534,16 @@ static inline void nohz_balance_exit_idle(int cpu)
static inline void set_cpu_sd_state_busy(void)
{
struct sched_domain *sd;
+ int cpu = smp_processor_id();
rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq()->sd);
+ sd = rcu_dereference(per_cpu(sd_busy, cpu));
if (!sd || !sd->nohz_idle)
goto unlock;
sd->nohz_idle = 0;
- for (; sd; sd = sd->parent)
- atomic_inc(&sd->groups->sgp->nr_busy_cpus);
+ atomic_inc(&sd->groups->sgp->nr_busy_cpus);
unlock:
rcu_read_unlock();
}
@@ -6551,16 +6551,16 @@ unlock:
void set_cpu_sd_state_idle(void)
{
struct sched_domain *sd;
+ int cpu = smp_processor_id();
rcu_read_lock();
- sd = rcu_dereference_check_sched_domain(this_rq()->sd);
+ sd = rcu_dereference(per_cpu(sd_busy, cpu));
if (!sd || sd->nohz_idle)
goto unlock;
sd->nohz_idle = 1;
- for (; sd; sd = sd->parent)
- atomic_dec(&sd->groups->sgp->nr_busy_cpus);
+ atomic_dec(&sd->groups->sgp->nr_busy_cpus);
unlock:
rcu_read_unlock();
}
@@ -6767,6 +6767,8 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
{
unsigned long now = jiffies;
struct sched_domain *sd;
+ struct sched_group_power *sgp;
+ int nr_busy;
if (unlikely(idle_cpu(cpu)))
return 0;
@@ -6792,22 +6794,22 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu)
goto need_kick;
rcu_read_lock();
- for_each_domain(cpu, sd) {
- struct sched_group *sg = sd->groups;
- struct sched_group_power *sgp = sg->sgp;
- int nr_busy = atomic_read(&sgp->nr_busy_cpus);
+ sd = rcu_dereference(per_cpu(sd_busy, cpu));
- if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1)
- goto need_kick_unlock;
+ if (sd) {
+ sgp = sd->groups->sgp;
+ nr_busy = atomic_read(&sgp->nr_busy_cpus);
- if (sd->flags & SD_ASYM_PACKING
- && (cpumask_first_and(nohz.idle_cpus_mask,
- sched_domain_span(sd)) < cpu))
+ if (nr_busy > 1)
goto need_kick_unlock;
-
- if (!(sd->flags & (SD_SHARE_PKG_RESOURCES | SD_ASYM_PACKING)))
- break;
}
+
+ sd = rcu_dereference(per_cpu(sd_asym, cpu));
+
+ if (sd && (cpumask_first_and(nohz.idle_cpus_mask,
+ sched_domain_span(sd)) < cpu))
+ goto need_kick_unlock;
+
rcu_read_unlock();
return 0;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 4e650acffed7..88c85b21d633 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -623,6 +623,8 @@ DECLARE_PER_CPU(struct sched_domain *, sd_llc);
DECLARE_PER_CPU(int, sd_llc_size);
DECLARE_PER_CPU(int, sd_llc_id);
DECLARE_PER_CPU(struct sched_domain *, sd_numa);
+DECLARE_PER_CPU(struct sched_domain *, sd_busy);
+DECLARE_PER_CPU(struct sched_domain *, sd_asym);
struct sched_group_power {
atomic_t ref;
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