linux-kernel - Re: [patch v8 6/9] sched: compute runnable load avg in cpu_load and cpu_avg_load_per

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Date:	Mon, 17 Jun 2013 05:17:17 -0700
From:	Paul Turner <pjt@...gle.com>
To:	Alex Shi <alex.shi@...el.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...en8.de>,
	Namhyung Kim <namhyung@...nel.org>,
	Mike Galbraith <efault@....de>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Preeti U Murthy <preeti@...ux.vnet.ibm.com>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mgorman@...e.de>, Rik van Riel <riel@...hat.com>,
	Michael Wang <wangyun@...ux.vnet.ibm.com>,
	Jason Low <jason.low2@...com>,
	Changlong Xie <changlongx.xie@...el.com>, sgruszka@...hat.com,
	Frédéric Weisbecker <fweisbec@...il.com>
Subject: Re: [patch v8 6/9] sched: compute runnable load avg in cpu_load and cpu_avg_load_per_task

On Mon, Jun 17, 2013 at 3:51 AM, Paul Turner <pjt@...gle.com> wrote:
> On Fri, Jun 7, 2013 at 12:20 AM, Alex Shi <alex.shi@...el.com> wrote:
>> They are the base values in load balance, update them with rq runnable
>> load average, then the load balance will consider runnable load avg
>> naturally.
>>
>> We also try to include the blocked_load_avg as cpu load in balancing,
>> but that cause kbuild performance drop 6% on every Intel machine, and
>> aim7/oltp drop on some of 4 CPU sockets machines.
>>
>
> This looks fine.
>
> Did you try including blocked_load_avg in only get_rq_runnable_load()
> [ and not weighted_cpuload() which is called by new-idle ]?

Looking at this more this feels less correct since you're taking
averages of averages.

This was previously discussed at:
  https://lkml.org/lkml/2013/5/6/109

And  you later replied suggesting this didn't seem to hurt; what's the
current status there?


>
>> Signed-off-by: Alex Shi <alex.shi@...el.com>
>> ---
>>  kernel/sched/fair.c |  5 +++--
>>  kernel/sched/proc.c | 17 +++++++++++++++--
>>  2 files changed, 18 insertions(+), 4 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 42c7be0..eadd2e7 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -2962,7 +2962,7 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>>  /* Used instead of source_load when we know the type == 0 */
>>  static unsigned long weighted_cpuload(const int cpu)
>>  {
>> -       return cpu_rq(cpu)->load.weight;
>> +       return cpu_rq(cpu)->cfs.runnable_load_avg;
>>  }
>>
>>  /*
>> @@ -3007,9 +3007,10 @@ static unsigned long cpu_avg_load_per_task(int cpu)
>>  {
>>         struct rq *rq = cpu_rq(cpu);
>>         unsigned long nr_running = ACCESS_ONCE(rq->nr_running);
>> +       unsigned long load_avg = rq->cfs.runnable_load_avg;
>>
>>         if (nr_running)
>> -               return rq->load.weight / nr_running;
>> +               return load_avg / nr_running;
>>
>>         return 0;
>>  }
>> diff --git a/kernel/sched/proc.c b/kernel/sched/proc.c
>> index bb3a6a0..ce5cd48 100644
>> --- a/kernel/sched/proc.c
>> +++ b/kernel/sched/proc.c
>> @@ -501,6 +501,18 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
>>         sched_avg_update(this_rq);
>>  }
>>
>> +#ifdef CONFIG_SMP
>> +unsigned long get_rq_runnable_load(struct rq *rq)
>> +{
>> +       return rq->cfs.runnable_load_avg;
>> +}
>> +#else
>> +unsigned long get_rq_runnable_load(struct rq *rq)
>> +{
>> +       return rq->load.weight;
>> +}
>> +#endif
>> +
>>  #ifdef CONFIG_NO_HZ_COMMON
>>  /*
>>   * There is no sane way to deal with nohz on smp when using jiffies because the
>> @@ -522,7 +534,7 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
>>  void update_idle_cpu_load(struct rq *this_rq)
>>  {
>>         unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
>> -       unsigned long load = this_rq->load.weight;
>> +       unsigned long load = get_rq_runnable_load(this_rq);
>>         unsigned long pending_updates;
>>
>>         /*
>> @@ -568,11 +580,12 @@ void update_cpu_load_nohz(void)
>>   */
>>  void update_cpu_load_active(struct rq *this_rq)
>>  {
>> +       unsigned long load = get_rq_runnable_load(this_rq);
>>         /*
>>          * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
>>          */
>>         this_rq->last_load_update_tick = jiffies;
>> -       __update_cpu_load(this_rq, this_rq->load.weight, 1);
>> +       __update_cpu_load(this_rq, load, 1);
>>
>>         calc_load_account_active(this_rq);
>>  }
>> --
>> 1.7.12
>>
--
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