On 20 December 2017 at 15:09, Peter Zijlstra <pet...@infradead.org> wrote:
> On Fri, Dec 01, 2017 at 06:01:56PM +0000, Brendan Jackman wrote:
>
>> @@ -9210,7 +9256,15 @@ static void nohz_idle_balance(struct rq *this_rq,
>> enum cpu_idle_type idle)
>> cpu_load_update_idle(rq);
>> rq_unlock_irq(rq, &rf);
>>
>> - rebalance_domains(rq, CPU_IDLE);
>> + update_blocked_averages(balance_cpu);
>> + /*
>> + * This idle load balance softirq may have been
>> + * triggered only to update the blocked load and shares
>> + * of idle CPUs (which we have just done for
>> + * balance_cpu). In that case skip the actual balance.
>> + */
>> + if (!in_nohz_stats_kick(this_cpu))
>> + rebalance_domains(rq, idle);
>> }
>>
>> if (time_after(next_balance, rq->next_balance)) {
>
>> @@ -9336,7 +9396,12 @@ static __latent_entropy void
>> run_rebalance_domains(struct softirq_action *h)
>> * and abort nohz_idle_balance altogether if we pull some load.
>> */
>> nohz_idle_balance(this_rq, idle);
>> - rebalance_domains(this_rq, idle);
>> + update_blocked_averages(this_rq->cpu);
>> + if (!in_nohz_stats_kick(this_rq->cpu))
>> + rebalance_domains(this_rq, idle);
>> +#ifdef CONFIG_NO_HZ_COMMON
>> + clear_bit(NOHZ_STATS_KICK, nohz_flags(this_rq->cpu));
>> +#endif
>> }
>>
>> /*
>
> You're doing the same thing to both (all) callsites of
> rebalance_domains(), does that not suggest doing it inside and leaving
> update_blocked_averages() where it is?
The goal of moving update_blocked_averages() outside rebalance_domains
is to not add a new parameter or use a special cpu_idle_type value in
rebalance_domains parameters in order to abort the rebalance sequence
just after updating blocked load
>
>
