[PATCH 06/30] sched: Factor out update_other_load_avgs() from __update_blocked_others()

Tejun Heo
2024-06-18T21:21:16Z

RT, DL, thermal and irq load and utilization metrics need to be decayed and
updated periodically and before consumption to keep the numbers reasonable.
This is currently done from __update_blocked_others() as a part of the fair
class load balance path. Let's factor it out to update_other_load_avgs().
Pure refactor. No functional changes.

This will be used by the new BPF extensible scheduling class to ensure that
the above metrics are properly maintained.

v2: Refreshed on top of tip:sched/core.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
---
kernel/sched/fair.c | 16 +++-------------
kernel/sched/sched.h | 4 ++++
kernel/sched/syscalls.c | 19 +++++++++++++++++++
3 files changed, 26 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 18ecd4f908e4..715d7c1f55df 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9352,28 +9352,18 @@ static inline void update_blocked_load_status(struct rq *rq, bool has_blocked) {

static bool __update_blocked_others(struct rq *rq, bool *done)
{
- const struct sched_class *curr_class;
- u64 now = rq_clock_pelt(rq);
- unsigned long hw_pressure;
- bool decayed;
+ bool updated;

/*
* update_load_avg() can call cpufreq_update_util(). Make sure that RT,
* DL and IRQ signals have been updated before updating CFS.
*/
- curr_class = rq->curr->sched_class;
-
- hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
-
- decayed = update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
- update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
- update_hw_load_avg(now, rq, hw_pressure) |
- update_irq_load_avg(rq, 0);
+ updated = update_other_load_avgs(rq);

if (others_have_blocked(rq))
*done = false;

- return decayed;
+ return updated;
}

#ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 656a63c0d393..a5a4f59151db 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3074,6 +3074,8 @@ static inline void cpufreq_update_util(struct rq *rq, unsigned int flags) { }

#ifdef CONFIG_SMP

+bool update_other_load_avgs(struct rq *rq);
+
unsigned long effective_cpu_util(int cpu, unsigned long util_cfs,
unsigned long *min,
unsigned long *max);
@@ -3117,6 +3119,8 @@ static inline unsigned long cpu_util_rt(struct rq *rq)
return READ_ONCE(rq->avg_rt.util_avg);
}

+#else /* !CONFIG_SMP */
+static inline bool update_other_load_avgs(struct rq *rq) { return false; }
#endif /* CONFIG_SMP */

#ifdef CONFIG_UCLAMP_TASK
diff --git a/kernel/sched/syscalls.c b/kernel/sched/syscalls.c
index cf189bc3dd18..050215ef8fa4 100644
--- a/kernel/sched/syscalls.c
+++ b/kernel/sched/syscalls.c
@@ -259,6 +259,25 @@ int sched_core_idle_cpu(int cpu)
#endif

#ifdef CONFIG_SMP
+/*
+ * Load avg and utiliztion metrics need to be updated periodically and before
+ * consumption. This function updates the metrics for all subsystems except for
+ * the fair class. @rq must be locked and have its clock updated.
+ */
+bool update_other_load_avgs(struct rq *rq)
+{
+ u64 now = rq_clock_pelt(rq);
+ const struct sched_class *curr_class = rq->curr->sched_class;
+ unsigned long hw_pressure = arch_scale_hw_pressure(cpu_of(rq));
+
+ lockdep_assert_rq_held(rq);
+
+ return update_rt_rq_load_avg(now, rq, curr_class == &rt_sched_class) |
+ update_dl_rq_load_avg(now, rq, curr_class == &dl_sched_class) |
+ update_hw_load_avg(now, rq, hw_pressure) |
+ update_irq_load_avg(rq, 0);
+}
+
/*
* This function computes an effective utilization for the given CPU, to be
* used for frequency selection given the linear relation: f = u * f_max.
--
2.45.2