linux-kernel - Re: [PATCH 10/14] sched: update the buddy CPU

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Date:	Mon, 29 Apr 2013 09:32:30 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Francesco Lavra <francescolavra.fl@...il.com>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	LAK <linux-arm-kernel@...ts.infradead.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Paul Turner <pjt@...gle.com>,
	Santosh <santosh.shilimkar@...com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	Chander Kashyap <chander.kashyap@...aro.org>,
	"cmetcalf@...era.com" <cmetcalf@...era.com>,
	"tony.luck@...el.com" <tony.luck@...el.com>,
	Alex Shi <alex.shi@...el.com>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Len Brown <len.brown@...el.com>,
	Lukasz Majewski <l.majewski@...sung.com>,
	Jonathan Corbet <corbet@....net>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH 10/14] sched: update the buddy CPU

On 28 April 2013 10:20, Francesco Lavra <francescolavra.fl@...il.com> wrote:
> Hi,
>
> On 04/25/2013 07:23 PM, Vincent Guittot wrote:
>> Periodically updates the buddy of a CPU according to the current activity of
>> the system. A CPU is its own buddy if it participates to the packing effort.
>> Otherwise, it points to a CPU that participates to the packing effort.
>>
>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>> ---
>>  kernel/sched/fair.c |   91 ++++++++++++++++++++++++++++++++++++++++++++++++---
>>  1 file changed, 86 insertions(+), 5 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 234ecdd..28f8ea7 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -174,11 +174,17 @@ void sched_init_granularity(void)
>>
>>
>>  #ifdef CONFIG_SMP
>> +static unsigned long power_of(int cpu)
>> +{
>> +     return cpu_rq(cpu)->cpu_power;
>> +}
>> +
>>  /*
>>   * Save the id of the optimal CPU that should be used to pack small tasks
>>   * The value -1 is used when no buddy has been found
>>   */
>>  DEFINE_PER_CPU(int, sd_pack_buddy);
>> +DEFINE_PER_CPU(struct sched_domain *, sd_pack_domain);
>>
>>  /*
>>   * Look for the best buddy CPU that can be used to pack small tasks
>> @@ -237,6 +243,68 @@ void update_packing_domain(int cpu)
>>       }
>>
>>       pr_debug("CPU%d packing on CPU%d\n", cpu, id);
>> +     per_cpu(sd_pack_domain, cpu) = sd;
>> +     per_cpu(sd_pack_buddy, cpu) = id;
>> +}
>> +
>> +void update_packing_buddy(int cpu, int activity)
>> +{
>> +     struct sched_domain *sd = per_cpu(sd_pack_domain, cpu);
>> +     struct sched_group *sg, *pack, *tmp;
>> +     int id = cpu;
>> +
>> +     if (!sd)
>> +             return;
>> +
>> +     /*
>> +      * The sched_domain of a CPU points on the local sched_group
>> +      * and this CPU of this local group is a good candidate
>> +      */
>> +     pack = sg = sd->groups;
>> +
>> +     /* loop the sched groups to find the best one */
>> +     for (tmp = sg->next; tmp != sg; tmp = tmp->next) {
>> +             if ((tmp->sgp->power * pack->group_weight) >
>> +                     (pack->sgp->power_available * tmp->group_weight))
>
> The power_available struct member is defined in a subsequent patch
> (12/14), so this patch series would break git bisect.

Hi Francesco,

yes, power_available should have been added in patch 13/14.
I will correct that

Thanks
Vincent

>
> --
> Francesco
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