diff options
| author | Ricardo Neri <ricardo.neri-calderon@linux.intel.com> | 2026-07-20 19:43:20 -0700 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2026-08-07 18:27:10 +0200 |
| commit | 0fbd428d078876cefe908efdbee47a4d5adc5f24 (patch) | |
| tree | 51c0d9dfd7c4746dfbd1dcdddfef4cb6361d8404 /kernel | |
| parent | 50b101f6e586b4417d060a976fd831cd87e86e2b (diff) | |
sched/fair: Skip misfit load accounting when the destination CPU cannot help
In domains with asymmetric capacity, identifying misfit load in a
scheduling group is not useful when the destination CPU cannot help (i.e.,
its capacity exceeds the group's maximum CPU capacity by less than ~5%). In
such cases, it also prevents load balance among clusters of equal capacity
when CONFIG_SCHED_CLUSTER is enabled. This happens because
update_sd_pick_busiest() skips candidate groups of type misfit_task if the
destination CPU has similar capacity.
Skipping misfit load accounting in this situation allows the group to be
classified as has_spare or fully_busy and lets load balancing proceed. Keep
marking scheduling groups as overloaded when misfit tasks are present. The
sg_overloaded flag propagates to the root domain and allows bigger CPUs in
it to help via newly idle balance.
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Tested-by: Christian Loehle <christian.loehle@arm.com>
Tested-by: Andrea Righi <arighi@nvidia.com>
Link: https://patch.msgid.link/20260720-rneri-fix-cas-clusters-v6-4-bb500bf4afd4@linux.intel.com
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 21 |
1 files changed, 17 insertions, 4 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index f9d0edd6828d..f1b4db36c23b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -11970,12 +11970,25 @@ static inline void update_sg_lb_stats(struct lb_env *env, continue; if (sd_flags & SD_ASYM_CPUCAPACITY) { - /* Check for a misfit task on the cpu */ - if (sgs->group_misfit_task_load < rq->misfit_task_load) { - sgs->group_misfit_task_load = rq->misfit_task_load; - + if (rq->misfit_task_load) { + /* + * Always mark the root domain overloaded so big + * CPUs can pick up misfit tasks via newly idle + * balance. + */ if (balancing_at_rd) *sg_overloaded = 1; + + /* + * Only account misfit load if @dst_cpu can + * help; otherwise, the group may be classified + * as misfit_task and update_sd_pick_busiest() + * will skip it. + */ + if (capacity_greater(capacity_of(env->dst_cpu), + group->sgc->max_capacity) && + (sgs->group_misfit_task_load < rq->misfit_task_load)) + sgs->group_misfit_task_load = rq->misfit_task_load; } } else if (env->idle && sched_reduced_capacity(rq, env->sd)) { /* Check for a task running on a CPU with reduced capacity */ |