[PATCH 6.18 019/314] sched/fair: Rename cfs_rq::avg_load to cfs_rq::sum_weight

Sasha Levin
2026-03-10T11:20:52Z

From: Ingo Molnar <mingo@kernel.org>

[ Upstream commit 4ff674fa986c27ec8a0542479258c92d361a2566 ]

The ::avg_load field is a long-standing misnomer: it says it's an
'average load', but in reality it's the momentary sum of the load
of all currently runnable tasks. We'd have to also perform a
division by nr_running (or use time-decay) to arrive at any sort
of average value.

This is clear from comments about the math of fair scheduling:

* \Sum w_i := cfs_rq->avg_load

The sum of all weights is ... the sum of all weights, not
the average of all weights.

To make it doubly confusing, there's also an ::avg_load
in the load-balancing struct sg_lb_stats, which *is* a
true average.

The second part of the field's name is a minor misnomer
as well: it says 'load', and it is indeed a load_weight
structure as it shares code with the load-balancer - but
it's only in an SMP load-balancing context where
load = weight, in the fair scheduling context the primary
purpose is the weighting of different nice levels.

So rename the field to ::sum_weight instead, which makes
the terminology of the EEVDF math match up with our
implementation of it:

* \Sum w_i := cfs_rq->sum_weight

Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://patch.msgid.link/20251201064647.1851919-6-mingo@kernel.org
Stable-dep-of: b3d99f43c72b ("sched/fair: Fix zero_vruntime tracking")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
kernel/sched/fair.c | 16 ++++++++--------
kernel/sched/sched.h | 2 +-
2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 82038166d7b0c..e68e894b57559 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -608,7 +608,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
*
* v0 := cfs_rq->zero_vruntime
* \Sum (v_i - v0) * w_i := cfs_rq->avg_vruntime
- * \Sum w_i := cfs_rq->avg_load
+ * \Sum w_i := cfs_rq->sum_weight
*
* Since zero_vruntime closely tracks the per-task service, these
* deltas: (v_i - v), will be in the order of the maximal (virtual) lag
@@ -625,7 +625,7 @@ avg_vruntime_add(struct cfs_rq *cfs_rq, struct sched_entity *se)
s64 key = entity_key(cfs_rq, se);

cfs_rq->avg_vruntime += key * weight;
- cfs_rq->avg_load += weight;
+ cfs_rq->sum_weight += weight;
}

static void
@@ -635,16 +635,16 @@ avg_vruntime_sub(struct cfs_rq *cfs_rq, struct sched_entity *se)
s64 key = entity_key(cfs_rq, se);

cfs_rq->avg_vruntime -= key * weight;
- cfs_rq->avg_load -= weight;
+ cfs_rq->sum_weight -= weight;
}

static inline
void avg_vruntime_update(struct cfs_rq *cfs_rq, s64 delta)
{
/*
- * v' = v + d ==> avg_vruntime' = avg_runtime - d*avg_load
+ * v' = v + d ==> avg_vruntime' = avg_runtime - d*sum_weight
*/
- cfs_rq->avg_vruntime -= cfs_rq->avg_load * delta;
+ cfs_rq->avg_vruntime -= cfs_rq->sum_weight * delta;
}

/*
@@ -655,7 +655,7 @@ u64 avg_vruntime(struct cfs_rq *cfs_rq)
{
struct sched_entity *curr = cfs_rq->curr;
s64 avg = cfs_rq->avg_vruntime;
- long load = cfs_rq->avg_load;
+ long load = cfs_rq->sum_weight;

if (curr && curr->on_rq) {
unsigned long weight = scale_load_down(curr->load.weight);
@@ -723,7 +723,7 @@ static int vruntime_eligible(struct cfs_rq *cfs_rq, u64 vruntime)
{
struct sched_entity *curr = cfs_rq->curr;
s64 avg = cfs_rq->avg_vruntime;
- long load = cfs_rq->avg_load;
+ long load = cfs_rq->sum_weight;

if (curr && curr->on_rq) {
unsigned long weight = scale_load_down(curr->load.weight);
@@ -5164,7 +5164,7 @@ place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
*
* vl_i = (W + w_i)*vl'_i / W
*/
- load = cfs_rq->avg_load;
+ load = cfs_rq->sum_weight;
if (curr && curr->on_rq)
load += scale_load_down(curr->load.weight);

diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 2f8b06b12a98f..20b2b7746c3c7 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -681,7 +681,7 @@ struct cfs_rq {
unsigned int h_nr_idle; /* SCHED_IDLE */

s64 avg_vruntime;
- u64 avg_load;
+ u64 sum_weight;

u64 zero_vruntime;
#ifdef CONFIG_SCHED_CORE
--
2.51.0