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Subject: Re: [RFC PATCH 1/3] sched/fair: Aggregate task utilization only on
 root cfs_rq
To: Juri Lelli <juri.lelli@arm.com>
References: <1464809962-25814-1-git-send-email-dietmar.eggemann@arm.com>
 <1464809962-25814-2-git-send-email-dietmar.eggemann@arm.com>
 <20160602092358.GC9340@e106622-lin>
Cc: Peter Zijlstra <peterz@infradead.org>, linux-kernel@vger.kernel.org,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Ben Segall <bsegall@google.com>,
        Morten Rasmussen <morten.rasmussen@arm.com>,
        Yuyang Du <yuyang.du@intel.com>
From: Dietmar Eggemann <dietmar.eggemann@arm.com>
Message-ID: <5750567F.6060601@arm.com>
Date: Thu, 2 Jun 2016 16:53:35 +0100
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On 02/06/16 10:23, Juri Lelli wrote:

>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 218f8e83db73..212becd3708f 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -2705,6 +2705,7 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
>>  	u32 contrib;
>>  	unsigned int delta_w, scaled_delta_w, decayed = 0;
>>  	unsigned long scale_freq, scale_cpu;
>> +	int update_util = 0;
>>  
>>  	delta = now - sa->last_update_time;
>>  	/*
>> @@ -2725,6 +2726,12 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
>>  		return 0;
>>  	sa->last_update_time = now;
>>  
>> +	if (cfs_rq) {
>> +		if (&rq_of(cfs_rq)->cfs == cfs_rq)
> 
> Maybe we can wrap this sort of checks in a static inline improving
> readability?

Something like this?

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 218f8e83db73..01b0fa689ef9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -251,6 +251,18 @@ static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
        return cfs_rq->rq;
 }
 
+/* cfs_rq "owned" by the root task group */
+static inline struct cfs_rq *root_rq_of(struct cfs_rq *cfs_rq)
+{
+       return &rq_of(cfs_rq)->cfs;
+}
+
+/* Is this cfs_rq "owned" by the root task group ? */
+static inline bool rq_is_root(struct cfs_rq *cfs_rq)
+{
+       return root_rq_of(cfs_rq) == cfs_rq;
+}
+
 /* An entity is a task if it doesn't "own" a runqueue */
 #define entity_is_task(se)     (!se->my_q)
 
@@ -376,6 +388,16 @@ static inline struct rq *rq_of(struct cfs_rq *cfs_rq)
        return container_of(cfs_rq, struct rq, cfs);
 }
 
+static inline struct cfs_rq *root_rq_of(struct cfs_rq *cfs_rq)
+{
+       return cfs_rq;
+}
+
+static inline bool rq_is_root(struct cfs_rq *cfs_rq)
+{
+       return true;
+}
+
 #define entity_is_task(se)     1