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Subject[PATCH -v2 10/18] sched/fair: Use reweight_entity() for set_user_nice()
From: Vincent Guittot <vincent.guittot@linaro.org>

Now that we directly change load_avg and propagate that change into
the sums, sys_nice() and co should do the same, otherwise its possible
to confuse load accounting when we migrate near the weight change.

[peterz: Changelog, call condition]
[josef: fixed runnable and !SMP compilation]
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20170517095045.GA8420@linaro.org
---
kernel/sched/core.c | 22 ++++++++++++-----
kernel/sched/fair.c | 63 +++++++++++++++++++++++++++++----------------------
kernel/sched/sched.h | 2 +
3 files changed, 54 insertions(+), 33 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -733,7 +733,7 @@ int tg_nop(struct task_group *tg, void *
}
#endif

-static void set_load_weight(struct task_struct *p)
+static void set_load_weight(struct task_struct *p, bool update_load)
{
int prio = p->static_prio - MAX_RT_PRIO;
struct load_weight *load = &p->se.load;
@@ -747,8 +747,16 @@ static void set_load_weight(struct task_
return;
}

- load->weight = scale_load(sched_prio_to_weight[prio]);
- load->inv_weight = sched_prio_to_wmult[prio];
+ /*
+ * 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);
+ } else {
+ load->weight = scale_load(sched_prio_to_weight[prio]);
+ load->inv_weight = sched_prio_to_wmult[prio];
+ }
}

static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
@@ -2356,7 +2364,7 @@ int sched_fork(unsigned long clone_flags
p->static_prio = NICE_TO_PRIO(0);

p->prio = p->normal_prio = __normal_prio(p);
- set_load_weight(p);
+ set_load_weight(p, false);

/*
* We don't need the reset flag anymore after the fork. It has
@@ -3803,7 +3811,7 @@ void set_user_nice(struct task_struct *p
put_prev_task(rq, p);

p->static_prio = NICE_TO_PRIO(nice);
- set_load_weight(p);
+ set_load_weight(p, true);
old_prio = p->prio;
p->prio = effective_prio(p);
delta = p->prio - old_prio;
@@ -3960,7 +3968,7 @@ static void __setscheduler_params(struct
*/
p->rt_priority = attr->sched_priority;
p->normal_prio = normal_prio(p);
- set_load_weight(p);
+ set_load_weight(p, true);
}

/* Actually do priority change: must hold pi & rq lock. */
@@ -5910,7 +5918,7 @@ void __init sched_init(void)
atomic_set(&rq->nr_iowait, 0);
}

- set_load_weight(&init_task);
+ set_load_weight(&init_task, false);

/*
* The boot idle thread does lazy MMU switching as well:
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2789,6 +2789,43 @@ static inline void
dequeue_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se) { }
#endif

+static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
+ unsigned long weight)
+{
+ if (se->on_rq) {
+ /* commit outstanding execution time */
+ if (cfs_rq->curr == se)
+ update_curr(cfs_rq);
+ account_entity_dequeue(cfs_rq, se);
+ dequeue_runnable_load_avg(cfs_rq, se);
+ }
+ dequeue_load_avg(cfs_rq, se);
+
+ update_load_set(&se->load, weight);
+
+#ifdef CONFIG_SMP
+ se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum,
+ LOAD_AVG_MAX - 1024 + se->avg.period_contrib);
+#endif
+
+ enqueue_load_avg(cfs_rq, se);
+ if (se->on_rq) {
+ account_entity_enqueue(cfs_rq, se);
+ enqueue_runnable_load_avg(cfs_rq, se);
+ }
+}
+
+void reweight_task(struct task_struct *p, int prio)
+{
+ struct sched_entity *se = &p->se;
+ struct cfs_rq *cfs_rq = cfs_rq_of(se);
+ struct load_weight *load = &se->load;
+ unsigned long weight = scale_load(sched_prio_to_weight[prio]);
+
+ reweight_entity(cfs_rq, se, weight);
+ load->inv_weight = sched_prio_to_wmult[prio];
+}
+
#ifdef CONFIG_FAIR_GROUP_SCHED
# ifdef CONFIG_SMP
/*
@@ -2892,32 +2929,6 @@ static long calc_cfs_shares(struct cfs_r
}
# endif /* CONFIG_SMP */

-static void reweight_entity(struct cfs_rq *cfs_rq, struct sched_entity *se,
- unsigned long weight)
-{
- if (se->on_rq) {
- /* commit outstanding execution time */
- if (cfs_rq->curr == se)
- update_curr(cfs_rq);
- account_entity_dequeue(cfs_rq, se);
- dequeue_runnable_load_avg(cfs_rq, se);
- }
- dequeue_load_avg(cfs_rq, se);
-
- update_load_set(&se->load, weight);
-
-#ifdef CONFIG_SMP
- se->avg.load_avg = div_u64(se_weight(se) * se->avg.load_sum,
- LOAD_AVG_MAX - 1024 + se->avg.period_contrib);
-#endif
-
- enqueue_load_avg(cfs_rq, se);
- if (se->on_rq) {
- account_entity_enqueue(cfs_rq, se);
- enqueue_runnable_load_avg(cfs_rq, se);
- }
-}
-
static inline int throttled_hierarchy(struct cfs_rq *cfs_rq);

static void update_cfs_shares(struct sched_entity *se)
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1532,6 +1532,8 @@ 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);


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