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

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Date:	Mon, 2 Jun 2014 16:07:52 +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 1 June 2014 13:33, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
> On 30/05/14 20:20, Vincent Guittot wrote:
>>
>> 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 ?
>
>
> No, not really but I still don't see (taken all your patches) where
> sds->total_activity is used.
>
> $ find . -name "*.[ch]" | xargs grep total_activity
> ./kernel/sched/fair.c:  unsigned long total_activity;  /* Total activity of
> all groups in sd */
> ./kernel/sched/fair.c:          .total_activity = 0UL,
> ./kernel/sched/fair.c:          sds->total_activity += sgs->group_activity;
>
> OOTH, sgs->group_activity is used to set sgs->group_capacity which is then
> used in if conditions in update_sd_pick_busiest(), update_sd_lb_stats() and
> find_busiest_group().

Sorry, i misread you 1st email and haven't understood that you were
specifically speaking about total_activity.
When i created the activity statistic, i have added both sg and sd
fields but i finally only use the sg one. If i don't need the sd field
after updating my patches, i will remove it

Thanks
Vincent

>
> [...]
>
>
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