github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-23 05:04:02 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

sched/fair: Skip misfit load accounting when the destination CPU cannot help

Browse Source 
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
This commit is contained in:
Ricardo Neri 2026-07-20 19:43:20 -07:00 committed by Peter Zijlstra
parent 50b101f6e5
commit 0fbd428d07
1 changed files with 17 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

21
kernel/sched/fair.c
View File

@ -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 */