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 <mingo@kernel.org> Reviewed-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Cc: "Gautham R. Shenoy" <gautham.shenoy@amd.com> Link: https://lore.kernel.org/r/20240308105901.1096078-4-mingo@kernel.org
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@ -5,8 +5,8 @@
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#include <linux/sched.h>
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enum cpu_idle_type {
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__CPU_NOT_IDLE = 0,
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CPU_IDLE,
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CPU_NOT_IDLE,
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CPU_NEWLY_IDLE,
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CPU_MAX_IDLE_TYPES
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};
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@ -9070,7 +9070,7 @@ static int detach_tasks(struct lb_env *env)
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* We don't want to steal all, otherwise we may be treated likewise,
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* which could at worst lead to a livelock crash.
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*/
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if (env->idle != CPU_NOT_IDLE && env->src_rq->nr_running <= 1)
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if (env->idle && env->src_rq->nr_running <= 1)
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break;
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env->loop++;
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@ -9803,7 +9803,7 @@ static inline bool smt_vs_nonsmt_groups(struct sched_group *sg1,
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static inline bool smt_balance(struct lb_env *env, struct sg_lb_stats *sgs,
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struct sched_group *group)
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{
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if (env->idle == CPU_NOT_IDLE)
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if (!env->idle)
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return false;
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/*
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@ -9827,7 +9827,7 @@ static inline long sibling_imbalance(struct lb_env *env,
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int ncores_busiest, ncores_local;
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long imbalance;
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if (env->idle == CPU_NOT_IDLE || !busiest->sum_nr_running)
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if (!env->idle || !busiest->sum_nr_running)
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return 0;
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ncores_busiest = sds->busiest->cores;
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@ -9927,8 +9927,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
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sgs->group_misfit_task_load = rq->misfit_task_load;
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*sg_status |= SG_OVERLOAD;
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}
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} else if ((env->idle != CPU_NOT_IDLE) &&
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sched_reduced_capacity(rq, env->sd)) {
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} else if (env->idle && sched_reduced_capacity(rq, env->sd)) {
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/* Check for a task running on a CPU with reduced capacity */
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if (sgs->group_misfit_task_load < load)
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sgs->group_misfit_task_load = load;
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@ -9940,7 +9939,7 @@ static inline void update_sg_lb_stats(struct lb_env *env,
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sgs->group_weight = group->group_weight;
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/* Check if dst CPU is idle and preferred to this group */
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if (!local_group && env->idle != CPU_NOT_IDLE && sgs->sum_h_nr_running &&
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if (!local_group && env->idle && sgs->sum_h_nr_running &&
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sched_group_asym(env, sgs, group))
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sgs->group_asym_packing = 1;
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@ -10698,7 +10697,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
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* waiting task in this overloaded busiest group. Let's
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* try to pull it.
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*/
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if (env->idle != CPU_NOT_IDLE && env->imbalance == 0) {
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if (env->idle && env->imbalance == 0) {
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env->migration_type = migrate_task;
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env->imbalance = 1;
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}
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@ -10913,7 +10912,7 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
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goto force_balance;
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if (busiest->group_type != group_overloaded) {
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if (env->idle == CPU_NOT_IDLE) {
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if (!env->idle) {
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/*
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* If the busiest group is not overloaded (and as a
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* result the local one too) but this CPU is already
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@ -11121,7 +11120,7 @@ asym_active_balance(struct lb_env *env)
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* the lower priority @env::dst_cpu help it. Do not follow
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* CPU priority.
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*/
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return env->idle != CPU_NOT_IDLE && sched_use_asym_prio(env->sd, env->dst_cpu) &&
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return env->idle && sched_use_asym_prio(env->sd, env->dst_cpu) &&
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(sched_asym_prefer(env->dst_cpu, env->src_cpu) ||
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!sched_use_asym_prio(env->sd, env->src_cpu));
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}
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@ -11159,7 +11158,7 @@ static int need_active_balance(struct lb_env *env)
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* because of other sched_class or IRQs if more capacity stays
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* available on dst_cpu.
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*/
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if ((env->idle != CPU_NOT_IDLE) &&
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if (env->idle &&
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(env->src_rq->cfs.h_nr_running == 1)) {
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if ((check_cpu_capacity(env->src_rq, sd)) &&
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(capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100))
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@ -11735,8 +11734,8 @@ static void rebalance_domains(struct rq *rq, enum cpu_idle_type idle)
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* env->dst_cpu, so we can't know our idle
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* state even if we migrated tasks. Update it.
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*/
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idle = idle_cpu(cpu) ? CPU_IDLE : CPU_NOT_IDLE;
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busy = idle != CPU_IDLE && !sched_idle_cpu(cpu);
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idle = idle_cpu(cpu);
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busy = !idle && !sched_idle_cpu(cpu);
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}
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sd->last_balance = jiffies;
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interval = get_sd_balance_interval(sd, busy);
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@ -12416,9 +12415,7 @@ out:
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static __latent_entropy void run_rebalance_domains(struct softirq_action *h)
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{
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struct rq *this_rq = this_rq();
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enum cpu_idle_type idle = this_rq->idle_balance ?
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CPU_IDLE : CPU_NOT_IDLE;
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enum cpu_idle_type idle = this_rq->idle_balance;
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/*
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* If this CPU has a pending nohz_balance_kick, then do the
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* balancing on behalf of the other idle CPUs whose ticks are
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