From 38d707c54df4ca58cd9ceae2ddcbd6f606b99e9f Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Fri, 8 Mar 2024 11:58:54 +0100 Subject: [PATCH] sched/balancing: Change 'enum cpu_idle_type' to have more natural definitions The cpu_idle_type enum has the confusingly inverted property that 'not idle' is 1, and 'idle' is '0'. This resulted in a number of unnecessary complications in the code. Reverse the order, remove the CPU_NOT_IDLE type, and convert all code to a natural boolean form. It's much more readable: - enum cpu_idle_type idle = this_rq->idle_balance ? - CPU_IDLE : CPU_NOT_IDLE; - + enum cpu_idle_type idle = this_rq->idle_balance; -------------------------------- - if (env->idle == CPU_NOT_IDLE || !busiest->sum_nr_running) + if (!env->idle || !busiest->sum_nr_running) -------------------------------- And gets rid of the double negation in these usages: - if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) + if (env->idle && env->src_rq->nr_running <= 1) Furthermore, this makes code much more obvious where there's differentiation between CPU_IDLE and CPU_NEWLY_IDLE. Signed-off-by: Ingo Molnar Reviewed-by: Valentin Schneider Reviewed-by: Vincent Guittot Cc: "Gautham R. Shenoy" Link: https://lore.kernel.org/r/20240308105901.1096078-4-mingo@kernel.org --- include/linux/sched/idle.h | 2 +- kernel/sched/fair.c | 27 ++++++++++++--------------- 2 files changed, 13 insertions(+), 16 deletions(-) diff --git a/include/linux/sched/idle.h b/include/linux/sched/idle.h index 478084f9105e..e670ac282333 100644 --- a/include/linux/sched/idle.h +++ b/include/linux/sched/idle.h @@ -5,8 +5,8 @@ #include enum cpu_idle_type { + __CPU_NOT_IDLE = 0, CPU_IDLE, - CPU_NOT_IDLE, CPU_NEWLY_IDLE, CPU_MAX_IDLE_TYPES }; diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2ef89b36aed1..3a510cf1fb00 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -9070,7 +9070,7 @@ static int detach_tasks(struct lb_env *env) * We don't want to steal all, otherwise we may be treated likewise, * which could at worst lead to a livelock crash. */ - if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1) + if (env->idle && env->src_rq->nr_running <= 1) break; env->loop++; @@ -9803,7 +9803,7 @@ static inline bool smt_vs_nonsmt_groups(struct sched_group *sg1, static inline bool smt_balance(struct lb_env *env, struct sg_lb_stats *sgs, struct sched_group *group) { - if (env->idle == CPU_NOT_IDLE) + if (!env->idle) return false; /* @@ -9827,7 +9827,7 @@ static inline long sibling_imbalance(struct lb_env *env, int ncores_busiest, ncores_local; long imbalance; - if (env->idle == CPU_NOT_IDLE || !busiest->sum_nr_running) + if (!env->idle || !busiest->sum_nr_running) return 0; ncores_busiest = sds->busiest->cores; @@ -9927,8 +9927,7 @@ static inline void update_sg_lb_stats(struct lb_env *env, sgs->group_misfit_task_load = rq->misfit_task_load; *sg_status |= SG_OVERLOAD; } - } else if ((env->idle != CPU_NOT_IDLE) && - sched_reduced_capacity(rq, env->sd)) { + } else if (env->idle && sched_reduced_capacity(rq, env->sd)) { /* Check for a task running on a CPU with reduced capacity */ if (sgs->group_misfit_task_load < load) sgs->group_misfit_task_load = load; @@ -9940,7 +9939,7 @@ static inline void update_sg_lb_stats(struct lb_env *env, sgs->group_weight = group->group_weight; /* Check if dst CPU is idle and preferred to this group */ - if (!local_group && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running && + if (!local_group && env->idle && sgs->sum_h_nr_running && sched_group_asym(env, sgs, group)) sgs->group_asym_packing = 1; @@ -10698,7 +10697,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s * waiting task in this overloaded busiest group. Let's * try to pull it. */ - if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) { + if (env->idle && env->imbalance == 0) { env->migration_type = migrate_task; env->imbalance = 1; } @@ -10913,7 +10912,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env) goto force_balance; if (busiest->group_type != group_overloaded) { - if (env->idle == CPU_NOT_IDLE) { + if (!env->idle) { /* * If the busiest group is not overloaded (and as a * result the local one too) but this CPU is already @@ -11121,7 +11120,7 @@ asym_active_balance(struct lb_env *env) * the lower priority @env::dst_cpu help it. Do not follow * CPU priority. */ - return env->idle != CPU_NOT_IDLE && sched_use_asym_prio(env->sd, env->dst_cpu) && + return env->idle && sched_use_asym_prio(env->sd, env->dst_cpu) && (sched_asym_prefer(env->dst_cpu, env->src_cpu) || !sched_use_asym_prio(env->sd, env->src_cpu)); } @@ -11159,7 +11158,7 @@ static int need_active_balance(struct lb_env *env) * because of other sched_class or IRQs if more capacity stays * available on dst_cpu. */ - if ((env->idle != CPU_NOT_IDLE) && + if (env->idle && (env->src_rq->cfs.h_nr_running == 1)) { if ((check_cpu_capacity(env->src_rq, sd)) && (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) @@ -11735,8 +11734,8 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle) * env->dst_cpu, so we can't know our idle * state even if we migrated tasks. Update it. */ - idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE; - busy = idle != CPU_IDLE && !sched_idle_cpu(cpu); + idle = idle_cpu(cpu); + busy = !idle && !sched_idle_cpu(cpu); } sd->last_balance = jiffies; interval = get_sd_balance_interval(sd, busy); @@ -12416,9 +12415,7 @@ static int newidle_balance(struct rq *this_rq, struct rq_flags *rf) static __latent_entropy void run_rebalance_domains(struct softirq_action *h) { struct rq *this_rq = this_rq(); - enum cpu_idle_type idle = this_rq->idle_balance ? - CPU_IDLE : CPU_NOT_IDLE; - + enum cpu_idle_type idle = this_rq->idle_balance; /* * If this CPU has a pending nohz_balance_kick, then do the * balancing on behalf of the other idle CPUs whose ticks are