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sched, sched_ext: Open code for_balance_class_range()

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For flexibility, sched_ext allows the BPF scheduler to select the CPU to
execute a task on at dispatch time so that e.g. a queue can be shared across
multiple CPUs. To enable this, the dispatch path is executed from balance()
so that a dispatched task can be hot-migrated to its target CPU. This means
that sched_ext needs its balance() method invoked before every
pick_next_task() even when the CPU is waking up from SCHED_IDLE.

for_balance_class_range() defined in kernel/sched/ext.h implements this
selective iteration promotion. However, the indirection obfuscates more than
helps. Open code the iteration promotion in put_prev_task_balance() and
remove for_balance_class_range().

No functional changes intended.

Signed-off-by: Tejun Heo <tj@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: David Vernet <void@manifault.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Tejun Heo 2024-07-08 09:39:48 -10:00
parent 6ab228ecc3
commit 744d83601f
2 changed files with 13 additions and 10 deletions
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14
kernel/sched/core.c
View File

@ -5825,7 +5825,19 @@ static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
struct rq_flags *rf)
{
#ifdef CONFIG_SMP
const struct sched_class *start_class = prev->sched_class;
const struct sched_class *class;
#ifdef CONFIG_SCHED_CLASS_EXT
/*
* SCX requires a balance() call before every pick_next_task() including
* when waking up from SCHED_IDLE. If @start_class is below SCX, start
* from SCX instead.
*/
if (sched_class_above(&ext_sched_class, start_class))
start_class = &ext_sched_class;
#endif
/*
* We must do the balancing pass before put_prev_task(), such
* that when we release the rq->lock the task is in the same
@ -5834,7 +5846,7 @@ static void put_prev_task_balance(struct rq *rq, struct task_struct *prev,
* We can terminate the balance pass as soon as we know there is
* a runnable task of @class priority or higher.
*/
for_balance_class_range(class, prev->sched_class, &idle_sched_class) {
for_active_class_range(class, start_class, &idle_sched_class) {
if (class->balance(rq, prev, rf))
break;
}

9
kernel/sched/ext.h
View File

@ -68,14 +68,6 @@ static inline const struct sched_class *next_active_class(const struct sched_cla
#define for_each_active_class(class) \
for_active_class_range(class, __sched_class_highest, __sched_class_lowest)
/*
* SCX requires a balance() call before every pick_next_task() call including
* when waking up from idle.
*/
#define for_balance_class_range(class, prev_class, end_class) \
for_active_class_range(class, (prev_class) > &ext_sched_class ? \
&ext_sched_class : (prev_class), (end_class))
#ifdef CONFIG_SCHED_CORE
bool scx_prio_less(const struct task_struct *a, const struct task_struct *b,
bool in_fi);
@ -100,7 +92,6 @@ static inline bool task_on_scx(const struct task_struct *p) { return false; }
static inline void init_sched_ext_class(void) {}
#define for_each_active_class for_each_class
#define for_balance_class_range for_class_range
#endif /* CONFIG_SCHED_CLASS_EXT */