kernel/sched/core.c | 5 +++++- kernel/sched/fair.c | 47 ++++++++++++++++++++++++++++++++++++++++--- kernel/sched/sched.h | 8 +++++++- 3 files changed, 57 insertions(+), 3 deletions(-)
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 46afe3af7ead57190b6d362e214814ec804e3b7b
Gitweb: https://git.kernel.org/tip/46afe3af7ead57190b6d362e214814ec804e3b7b
Author: Tim Chen <tim.c.chen@linux.intel.com>
AuthorDate: Wed, 01 Apr 2026 14:52:19 -07:00
Committer: Peter Zijlstra <peterz@infradead.org>
CommitterDate: Thu, 09 Apr 2026 15:49:49 +02:00
sched/cache: Track LLC-preferred tasks per runqueue
For each runqueue, track the number of tasks with an LLC preference
and how many of them are running on their preferred LLC. This mirrors
nr_numa_running and nr_preferred_running for NUMA balancing, and will
be used by cache-aware load balancing in later patches.
Co-developed-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Chen Yu <yu.c.chen@intel.com>
Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/459a37102f3d74a4e09ea58401d2094ac731d044.1775065312.git.tim.c.chen@linux.intel.com
---
kernel/sched/core.c | 5 +++++-
kernel/sched/fair.c | 47 ++++++++++++++++++++++++++++++++++++++++---
kernel/sched/sched.h | 8 +++++++-
3 files changed, 57 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d11e27b..eb542c9 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -539,6 +539,11 @@ void __trace_set_current_state(int state_value)
}
EXPORT_SYMBOL(__trace_set_current_state);
+int task_llc(const struct task_struct *p)
+{
+ return per_cpu(sd_llc_id, task_cpu(p));
+}
+
/*
* Serialization rules:
*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6e78ecf..e66da7a 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1384,6 +1384,30 @@ static int llc_id(int cpu)
return per_cpu(sd_llc_id, cpu);
}
+static void account_llc_enqueue(struct rq *rq, struct task_struct *p)
+{
+ int pref_llc;
+
+ pref_llc = p->preferred_llc;
+ if (pref_llc < 0)
+ return;
+
+ rq->nr_llc_running++;
+ rq->nr_pref_llc_running += (pref_llc == task_llc(p));
+}
+
+static void account_llc_dequeue(struct rq *rq, struct task_struct *p)
+{
+ int pref_llc;
+
+ pref_llc = p->preferred_llc;
+ if (pref_llc < 0)
+ return;
+
+ rq->nr_llc_running--;
+ rq->nr_pref_llc_running -= (pref_llc == task_llc(p));
+}
+
void mm_init_sched(struct mm_struct *mm,
struct sched_cache_time __percpu *_pcpu_sched)
{
@@ -1490,6 +1514,8 @@ static int get_pref_llc(struct task_struct *p, struct mm_struct *mm)
return mm_sched_llc;
}
+static unsigned int task_running_on_cpu(int cpu, struct task_struct *p);
+
static inline
void account_mm_sched(struct rq *rq, struct task_struct *p, s64 delta_exec)
{
@@ -1530,8 +1556,13 @@ void account_mm_sched(struct rq *rq, struct task_struct *p, s64 delta_exec)
mm_sched_llc = get_pref_llc(p, mm);
- if (READ_ONCE(p->preferred_llc) != mm_sched_llc)
+ /* task not on rq accounted later in account_entity_enqueue() */
+ if (task_running_on_cpu(rq->cpu, p) &&
+ READ_ONCE(p->preferred_llc) != mm_sched_llc) {
+ account_llc_dequeue(rq, p);
WRITE_ONCE(p->preferred_llc, mm_sched_llc);
+ account_llc_enqueue(rq, p);
+ }
}
static void task_tick_cache(struct rq *rq, struct task_struct *p)
@@ -1714,6 +1745,10 @@ static inline int get_pref_llc(struct task_struct *p,
return -1;
}
+static void account_llc_enqueue(struct rq *rq, struct task_struct *p) {}
+
+static void account_llc_dequeue(struct rq *rq, struct task_struct *p) {}
+
#endif /* CONFIG_SCHED_CACHE */
/*
@@ -4200,9 +4235,11 @@ account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
update_load_add(&cfs_rq->load, se->load.weight);
if (entity_is_task(se)) {
+ struct task_struct *p = task_of(se);
struct rq *rq = rq_of(cfs_rq);
- account_numa_enqueue(rq, task_of(se));
+ account_numa_enqueue(rq, p);
+ account_llc_enqueue(rq, p);
list_add(&se->group_node, &rq->cfs_tasks);
}
cfs_rq->nr_queued++;
@@ -4213,7 +4250,11 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
update_load_sub(&cfs_rq->load, se->load.weight);
if (entity_is_task(se)) {
- account_numa_dequeue(rq_of(cfs_rq), task_of(se));
+ struct task_struct *p = task_of(se);
+ struct rq *rq = rq_of(cfs_rq);
+
+ account_numa_dequeue(rq, p);
+ account_llc_dequeue(rq, p);
list_del_init(&se->group_node);
}
cfs_rq->nr_queued--;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 3cb3ab0..3c9e92b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1196,6 +1196,12 @@ struct rq {
#ifdef CONFIG_NUMA_BALANCING
unsigned int numa_migrate_on;
#endif
+
+#ifdef CONFIG_SCHED_CACHE
+ unsigned int nr_pref_llc_running;
+ unsigned int nr_llc_running;
+#endif
+
/*
* This is part of a global counter where only the total sum
* over all CPUs matters. A task can increase this counter on
@@ -2077,6 +2083,8 @@ init_numa_balancing(u64 clone_flags, struct task_struct *p)
#endif /* !CONFIG_NUMA_BALANCING */
+int task_llc(const struct task_struct *p);
+
static inline void
queue_balance_callback(struct rq *rq,
struct balance_callback *head,© 2016 - 2026 Red Hat, Inc.