On 02/08/2020 06:51, Qi Zheng wrote:
> I think the unbalance scenario here should be that we need to
> do active balance but it is not actually done. So fix it.
>
> Signed-off-by: Qi Zheng <arch0.zh...@gmail.com>
> ---
> kernel/sched/fair.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 2ba8f230feb9..6d8c53718b67 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -9710,7 +9710,7 @@ static int load_balance(int this_cpu, struct rq
> *this_rq,
> } else
> sd->nr_balance_failed = 0;
>
> - if (likely(!active_balance) || voluntary_active_balance(&env)) {
> + if (likely(!active_balance) && voluntary_active_balance(&env)) {
> /* We were unbalanced, so reset the balancing interval */
> sd->balance_interval = sd->min_interval;
> } else {
>
Active balance is potentially already been done when we reach this code.
See 'if (need_active_balance(&env))' and 'if (!busiest->active_balance)'
further up.
Here we only reset sd->balance_interval in case:
(A) the last load balance wasn't an active one
(B) the reason for the active load balance was:
(1) asym packing
(2) capacity of src_cpu is reduced compared to the one of dst_cpu
(3) misfit handling
(B) is done to not unnecessarily increase of balance interval, see
commit 46a745d90585 ("sched/fair: Fix unnecessary increase of balance
interval").
