Messages in this thread | | | Subject | Re: [PATCH] sched/fair: Fix the logic about active_balance in load_balance() | From | Qi Zheng <> | Date | Mon, 3 Aug 2020 20:33:58 +0800 |
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Hi Dietmar,
I understand, thank you for your review and very detailed explanation.
Yours, Qi Zheng
On 2020/8/3 下午3:36, Dietmar Eggemann wrote: > 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.zheng@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"). >
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