diff options
| author | Ricardo Neri <ricardo.neri-calderon@linux.intel.com> | 2026-07-20 19:43:17 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-08-07 18:27:09 +0200 |
| commit | 180ff97c186971c2106e68470e4370ace0b8fbbc (patch) | |
| tree | 229a62ca2852311199ad4d5be4f1df69d11d0e4c /kernel | |
| parent | 293f9611ae73564febc553935830074f0f300694 (diff) | |
sched/fair: Do not skip CPUs of similar capacity with busy SMT siblings
When picking a busiest CPU with only one running task, the function
sched_balance_find_src_rq() skips candidate CPUs if the destination CPU has
less than ~5% extra capacity. This condition only holds if all the SMT
siblings of a CPU are idle.
SMT siblings share the computing resources of a physical core and this
results in reduced capacity if more than one sibling is busy.
Skipping a CPU as described would prevent the load balancer from pulling
tasks from a scheduling group previously and correctly identified as
group_smt_balance (i.e., one with more than one task running).
Do not skip a candidate CPU of similar capacity if it has busy SMT
siblings.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Andrea Righi <arighi@nvidia.com>
Link: https://patch.msgid.link/20260720-rneri-fix-cas-clusters-v6-1-bb500bf4afd4@linux.intel.com
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 14 |
1 files changed, 11 insertions, 3 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index a24dd2089ae9..974e091e9d66 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -13086,9 +13086,17 @@ static struct rq *sched_balance_find_src_rq(struct lb_env *env, * average load. */ if (env->sd->flags & SD_ASYM_CPUCAPACITY && - !capacity_greater(capacity_of(env->dst_cpu), capacity) && - nr_running == 1) - continue; + nr_running == 1) { + bool smt_degraded_cap = sched_smt_active() && !is_core_idle(i); + + /* + * Busy SMT siblings reduce the capacity of CPU @i. Do + * not skip it in this case. + */ + if (!smt_degraded_cap && + !capacity_greater(capacity_of(env->dst_cpu), capacity)) + continue; + } /* * Make sure we only pull tasks from a CPU of lower priority |