diff options
| author | K Prateek Nayak <kprateek.nayak@amd.com> | 2026-05-09 20:07:29 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-05-19 12:17:39 +0200 |
| commit | 61ea17a63719bac51e1bc50eb39fc637f0fdc06e (patch) | |
| tree | 49483f864451fa7c89d7b66ca6847ffb57da6ab6 /kernel/sched | |
| parent | bf6aa722198d3c06e4236e8c5a480f30a64e1513 (diff) | |
sched/fair: Add SIS_UTIL support to select_idle_capacity()
Add to select_idle_capacity() the same SIS_UTIL-controlled idle-scan
mechanism, already used by select_idle_cpu(): when sched_feat(SIS_UTIL)
is enabled and the LLC domain has sched_domain_shared data, derive the
per-attempt scan limit from sd->shared->nr_idle_scan.
That bounds the walk on large LLCs: once nr_idle_scan is exhausted,
return the best CPU seen so far. The early exit is gated on
!has_idle_core so an active idle-core search (SMT with idle cores
reported by test_idle_cores()) isn't cut short before it gets a chance
to find one.
Co-developed-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Link: https://patch.msgid.link/20260509180955.1840064-6-arighi@nvidia.com
Diffstat (limited to 'kernel/sched')
| -rw-r--r-- | kernel/sched/fair.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f69ee5ae2b8c..69ba882681c5 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8016,6 +8016,7 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) int fits, best_fits = ASYM_IDLE_THREAD_MISFIT; int cpu, best_cpu = -1; struct cpumask *cpus; + int nr = INT_MAX; cpus = this_cpu_cpumask_var_ptr(select_rq_mask); cpumask_and(cpus, sched_domain_span(sd), p->cpus_ptr); @@ -8024,10 +8025,28 @@ select_idle_capacity(struct task_struct *p, struct sched_domain *sd, int target) util_min = uclamp_eff_value(p, UCLAMP_MIN); util_max = uclamp_eff_value(p, UCLAMP_MAX); + if (sched_feat(SIS_UTIL) && sd->shared) { + /* + * Same nr_idle_scan hint as select_idle_cpu(), nr only limits + * the scan when not preferring an idle core. + */ + nr = READ_ONCE(sd->shared->nr_idle_scan) + 1; + /* overloaded domain is unlikely to have idle cpu/core */ + if (nr == 1) + return -1; + } + for_each_cpu_wrap(cpu, cpus, target) { bool preferred_core = !has_idle_core || is_core_idle(cpu); unsigned long cpu_cap = capacity_of(cpu); + /* + * Stop when the nr_idle_scan is exhausted (mirrors + * select_idle_cpu() logic). + */ + if (!has_idle_core && --nr <= 0) + return best_cpu; + if (!choose_idle_cpu(cpu, p)) continue; |