From: Preeti U Murthy <[email protected]> This patch has been added to the 3.12 stable tree. If you have any objections, please let us know.
=============== 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<[email protected]> Signed-off-by: Peter Zijlstra <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/[email protected] Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Jiri Slaby <[email protected]> --- kernel/sched/core.c | 6 ++++++ kernel/sched/fair.c | 38 ++++++++++++++++++++------------------ kernel/sched/sched.h | 2 ++ 3 files changed, 28 insertions(+), 18 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ceae65e69a64..6135b7c6bcfe 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5119,6 +5119,8 @@ static void destroy_sched_domains(struct sched_domain *sd, int cpu) 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_busy); +DEFINE_PER_CPU(struct sched_domain *, sd_asym); static void update_top_cache_domain(int cpu) { @@ -5130,11 +5132,15 @@ 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); per_cpu(sd_llc_size, cpu) = size; per_cpu(sd_llc_id, cpu) = id; + + 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 68648f652dca..bbfb3dc53eb4 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -5598,16 +5598,16 @@ 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(); } @@ -5615,16 +5615,16 @@ 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(); } @@ -5807,6 +5807,8 @@ 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; @@ -5832,22 +5834,22 @@ 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 a6208afd80e7..4f310592b1ba 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -596,6 +596,8 @@ static inline struct sched_domain *highest_flag_domain(int cpu, int flag) 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_busy); +DECLARE_PER_CPU(struct sched_domain *, sd_asym); struct sched_group_power { atomic_t ref; -- 1.9.0 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
