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sched/balancing: Change 'enum cpu_idle_type' to have more natural definitions

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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
This commit is contained in:
Ingo Molnar 2024-03-08 11:58:54 +01:00
parent 02a61f325a
commit 38d707c54d
2 changed files with 13 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

2
include/linux/sched/idle.h
View file

@ -5,8 +5,8 @@
#include <linux/sched.h>
enum cpu_idle_type {
__CPU_NOT_IDLE = 0,
CPU_IDLE,
CPU_NOT_IDLE,
CPU_NEWLY_IDLE,
CPU_MAX_IDLE_TYPES
};

27
kernel/sched/fair.c
View file

@ -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