diff options
| author | Maria Yu <aiquny@codeaurora.org> | 2019-04-26 15:20:18 +0800 |
|---|---|---|
| committer | Georg Veichtlbauer <georg@vware.at> | 2023-07-16 12:47:43 +0200 |
| commit | eccc8acbe705a20e0911ea776371d84eba53cc8e (patch) | |
| tree | d04a1bd51f4395e14c17eb96f9bffb53e3348937 /kernel | |
| parent | 0ffdb886996b66e1eb9bbda6e9605bf7dbca0cd1 (diff) | |
sched/fair: Avoid unnecessary active load balance
When find busiest group, it will avoid load balance if
it is only 1 task running on src cpu. Consider race when
different cpus do newly idle load balance at the same time,
check src cpu nr_running to avoid unnecessary active load
balance again.
See the race condition example here:
1) cpu2 have 2 tasks, so cpu2 rq->nr_running == 2 and cfs.h_nr_running
==2.
2) cpu4 and cpu5 doing newly idle load balance at the same time.
3) cpu4 and cpu5 both see cpu2 sched_load_balance_sg_stats sum_nr_run=2
so they are both see cpu2 as the busiest rq.
4) cpu5 did a success migration task from cpu2, so cpu2 only have 1 task
left, cpu2 rq->nr_running == 1 and cfs.h_nr_running ==1.
5) cpu4 surely goes to no_move because currently cpu4 only have 1 task
which is currently running.
6) and then cpu4 goes here to check if cpu2 need active load balance.
Change-Id: Ia9539a43e9769c4936f06ecfcc11864984c50c29
Signed-off-by: Maria Yu <aiquny@codeaurora.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 941424604fdd..42f05c742846 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -10456,8 +10456,10 @@ static int need_active_balance(struct lb_env *env) * It's worth migrating the task if the src_cpu's capacity is reduced * because of other sched_class or IRQs if more capacity stays * available on dst_cpu. + * Avoid pulling the CFS task if it is the only task running. */ if ((env->idle != CPU_NOT_IDLE) && + (env->src_rq->nr_running > 1) && (env->src_rq->cfs.h_nr_running == 1)) { if ((check_cpu_capacity(env->src_rq, sd)) && (capacity_of(env->src_cpu)*sd->imbalance_pct < capacity_of(env->dst_cpu)*100)) |