Messages in this thread Patch in this message | | | From | Valentin Schneider <> | Subject | [PATCH v2 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan | Date | Wed, 11 Mar 2020 18:16:01 +0000 |
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Reworking select_task_rq_fair()'s domain walk exposed that !want_affine wakeups only look for highest sched_domain with the required sd_flag set. This is something we can cache at sched domain build time to slightly optimize select_task_rq_fair(). Note that this isn't a "free" optimization: it costs us 3 pointers per CPU.
Add cached per-CPU pointers for the highest domains with SD_BALANCE_WAKE, SD_BALANCE_EXEC and SD_BALANCE_FORK. Use them in select_task_rq_fair().
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com> --- kernel/sched/fair.c | 25 +++++++++++++------------ kernel/sched/sched.h | 3 +++ kernel/sched/topology.c | 12 ++++++++++++ 3 files changed, 28 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a6fca6817e92..40fb97062157 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6595,17 +6595,6 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) int want_affine = 0; int sd_flag; - switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) { - case WF_TTWU: - sd_flag = SD_BALANCE_WAKE; - break; - case WF_FORK: - sd_flag = SD_BALANCE_FORK; - break; - default: - sd_flag = SD_BALANCE_EXEC; - } - if (wake_flags & WF_TTWU) { record_wakee(p); @@ -6621,7 +6610,19 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int wake_flags) rcu_read_lock(); - sd = highest_flag_domain(cpu, sd_flag); + switch (wake_flags & (WF_TTWU | WF_FORK | WF_EXEC)) { + case WF_TTWU: + sd_flag = SD_BALANCE_WAKE; + sd = rcu_dereference(per_cpu(sd_balance_wake, cpu)); + break; + case WF_FORK: + sd_flag = SD_BALANCE_FORK; + sd = rcu_dereference(per_cpu(sd_balance_fork, cpu)); + break; + default: + sd_flag = SD_BALANCE_EXEC; + sd = rcu_dereference(per_cpu(sd_balance_exec, cpu)); + } /* * If !want_affine, we just look for the highest domain where diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ad2106245e12..3a0e38f2f713 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1393,6 +1393,9 @@ DECLARE_PER_CPU(int, sd_llc_size); DECLARE_PER_CPU(int, sd_llc_id); DECLARE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared); DECLARE_PER_CPU(struct sched_domain __rcu *, sd_numa); +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_wake); +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_fork); +DECLARE_PER_CPU(struct sched_domain __rcu *, sd_balance_exec); DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing); DECLARE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity); extern struct static_key_false sched_asym_cpucapacity; diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 6077b23f9723..0270252a964b 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -610,6 +610,9 @@ DEFINE_PER_CPU(int, sd_llc_size); DEFINE_PER_CPU(int, sd_llc_id); DEFINE_PER_CPU(struct sched_domain_shared __rcu *, sd_llc_shared); DEFINE_PER_CPU(struct sched_domain __rcu *, sd_numa); +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_wake); +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_fork); +DEFINE_PER_CPU(struct sched_domain __rcu *, sd_balance_exec); DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_packing); DEFINE_PER_CPU(struct sched_domain __rcu *, sd_asym_cpucapacity); DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity); @@ -636,6 +639,15 @@ 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_BALANCE_WAKE); + rcu_assign_pointer(per_cpu(sd_balance_wake, cpu), sd); + + sd = highest_flag_domain(cpu, SD_BALANCE_FORK); + rcu_assign_pointer(per_cpu(sd_balance_fork, cpu), sd); + + sd = highest_flag_domain(cpu, SD_BALANCE_EXEC); + rcu_assign_pointer(per_cpu(sd_balance_exec, cpu), sd); + sd = highest_flag_domain(cpu, SD_ASYM_PACKING); rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd); -- 2.24.0
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