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sched: Add sched_class->reweight_task()

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Currently, during a task weight change, sched core directly calls
reweight_task() defined in fair.c if @p is on CFS. Let's make it a proper
sched_class operation instead. CFS's reweight_task() is renamed to
reweight_task_fair() and now called through sched_class.

While it turns a direct call into an indirect one, set_load_weight() isn't
called from a hot path and this change shouldn't cause any noticeable
difference. This will be used to implement reweight_task for a new BPF
extensible sched_class so that it can keep its cached task weight
up-to-date.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Acked-by: Josh Don <joshdon@google.com>
Acked-by: Hao Luo <haoluo@google.com>
Acked-by: Barret Rhoden <brho@google.com>
This commit is contained in:
Tejun Heo 2024-06-18 10:09:16 -10:00
parent 304b3f2bc0
commit e83edbf88f
3 changed files with 6 additions and 5 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

4
kernel/sched/core.c
View file

@ -1343,8 +1343,8 @@ void set_load_weight(struct task_struct *p, bool update_load)
* SCHED_OTHER tasks have to update their load when changing their
* weight
*/
if (update_load && p->sched_class == &fair_sched_class) {
reweight_task(p, prio);
if (update_load && p->sched_class->reweight_task) {
p->sched_class->reweight_task(task_rq(p), p, prio);
} else {
load->weight = scale_load(sched_prio_to_weight[prio]);
load->inv_weight = sched_prio_to_wmult[prio];

3
kernel/sched/fair.c
View file

@ -3835,7 +3835,7 @@ static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
}
}
void reweight_task(struct task_struct *p, int prio)
static void reweight_task_fair(struct rq *rq, struct task_struct *p, int prio)
{
struct sched_entity *se = &p->se;
struct cfs_rq *cfs_rq = cfs_rq_of(se);
@ -13221,6 +13221,7 @@ DEFINE_SCHED_CLASS(fair) = {
.task_tick = task_tick_fair,
.task_fork = task_fork_fair,
.reweight_task = reweight_task_fair,
.prio_changed = prio_changed_fair,
.switched_from = switched_from_fair,
.switched_to = switched_to_fair,

4
kernel/sched/sched.h
View file

@ -2324,6 +2324,8 @@ struct sched_class {
*/
void (*switched_from)(struct rq *this_rq, struct task_struct *task);
void (*switched_to) (struct rq *this_rq, struct task_struct *task);
void (*reweight_task)(struct rq *this_rq, struct task_struct *task,
int newprio);
void (*prio_changed) (struct rq *this_rq, struct task_struct *task,
int oldprio);
@ -2509,8 +2511,6 @@ extern void init_sched_dl_class(void);
extern void init_sched_rt_class(void);
extern void init_sched_fair_class(void);
extern void reweight_task(struct task_struct *p, int prio);
extern void resched_curr(struct rq *rq);
extern void resched_cpu(int cpu);