sched: Add sched_class->reweight_task()

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>

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 0956044..48f9d00 100644 (file)
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -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];

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 41b5838..18ecd4f 100644 (file)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -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,

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 62fd8bc..a2399cc 100644 (file)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -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);