linux-kernel - Re: [PATCH v2 08/11] sched: get CPU's activity statistic

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Date:	Fri, 30 May 2014 21:20:40 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Dietmar Eggemann <dietmar.eggemann@....com>
Cc:	"peterz@...radead.org" <peterz@...radead.org>,
	"mingo@...nel.org" <mingo@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"preeti@...ux.vnet.ibm.com" <preeti@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"efault@....de" <efault@....de>,
	"nicolas.pitre@...aro.org" <nicolas.pitre@...aro.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
Subject: Re: [PATCH v2 08/11] sched: get CPU's activity statistic

On 30 May 2014 11:50, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> On 23/05/14 16:53, Vincent Guittot wrote:
>> Monitor the activity level of each group of each sched_domain level. The
>> activity is the amount of cpu_power that is currently used on a CPU or group
>> of CPUs. We use the runnable_avg_sum and _period to evaluate this activity
>> level. In the special use case where the CPU is fully loaded by more than 1
>> task, the activity level is set above the cpu_power in order to reflect the
>> overload of the CPU
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>
> [...]
>
>>  /*
>>   * select_task_rq_fair: Select target runqueue for the waking task in domains
>>   * that have the 'sd_flag' flag set. In practice, this is SD_BALANCE_WAKE,
>> @@ -5518,6 +5535,7 @@ struct sg_lb_stats {
>>       unsigned long sum_weighted_load; /* Weighted load of group's tasks */
>>       unsigned long load_per_task;
>>       unsigned long group_power;
>> +     unsigned long group_activity; /* Total activity of the group */
>>       unsigned int sum_nr_running; /* Nr tasks running in the group */
>>       unsigned int group_capacity;
>>       unsigned int idle_cpus;
>> @@ -5538,6 +5556,7 @@ struct sd_lb_stats {
>>       struct sched_group *busiest;    /* Busiest group in this sd */
>>       struct sched_group *local;      /* Local group in this sd */
>>       unsigned long total_load;       /* Total load of all groups in sd */
>> +     unsigned long total_activity;  /* Total activity of all groups in sd */
>>       unsigned long total_pwr;        /* Total power of all groups in sd */
>>       unsigned long avg_load; /* Average load across all groups in sd */
>>
>> @@ -5557,6 +5576,7 @@ static inline void init_sd_lb_stats(struct sd_lb_stats *sds)
>>               .busiest = NULL,
>>               .local = NULL,
>>               .total_load = 0UL,
>> +             .total_activity = 0UL,
>
> AFAICS, total_activity is not used right now. Do you intend to use it to
> calculate something like avg_activity later (like total_load/avg_load)?

this patch only creates group_activity and total_activity.The use of
these statistics appears on the next patches. I have not planned to
compute such avg_activity for the moment mainly because i have need it
yet.

Do you have in mind any use of such avg_activity ?

Vincent

>
>>               .total_pwr = 0UL,
>>               .busiest_stat = {
>>                       .avg_load = 0UL,
>
> [...]
>
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