Re: [PATCH v7 3/7] sched: add utilization_avg_contrib

[Dietmar Eggemann <dietmar.eggemann@arm.com>]

On 07/10/14 13:13, Vincent Guittot wrote:
> Add new statistics which reflect the average time a task is running on the CPU
> and the sum of these running time of the tasks on a runqueue. The latter is
> named utilization_avg_contrib.
> 
> This patch is based on the usage metric that was proposed in the 1st
> versions of the per-entity load tracking patchset by Paul Turner
> <pjt@google.com> but that has be removed afterward. This version differs
> from the original one in the sense that it's not linked to task_group.
> 
> The rq's utilization_avg_contrib will be used to check if a rq is overloaded
> or not instead of trying to compute how many task a group of CPUs can handle
> 
> Rename runnable_avg_period into avg_period as it is now used with both
> runnable_avg_sum and running_avg_sum
> 
> Add some descriptions of the variables to explain their differences
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>  include/linux/sched.h | 21 +++++++++++++---
>  kernel/sched/debug.c  |  9 ++++---
>  kernel/sched/fair.c   | 70 +++++++++++++++++++++++++++++++++++++++------------
>  kernel/sched/sched.h  |  8 +++++-
>  4 files changed, 84 insertions(+), 24 deletions(-)
> 

[...]

> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9075dee..d6de526 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -678,8 +678,8 @@ void init_task_runnable_average(struct task_struct *p)
> 
>         p->se.avg.decay_count = 0;
>         slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
> -       p->se.avg.runnable_avg_sum = slice;
> -       p->se.avg.runnable_avg_period = slice;
> +       p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = slice;
> +       p->se.avg.avg_period = slice;
>         __update_task_entity_contrib(&p->se);

Didn't you miss a call to __update_task_entity_utilization here?

Another thing from the naming perspective: You use the term
'utilization' for 'load' (e.g. existing __update_entity_load_avg_contrib
versus new __update_entity_utilization_avg_contrib) but for the
__update_task_entity_contrib function, you use the term 'utilization'
for 'contrib'. IMHO, kind of hard to grasp.

>  }
>  #else
> @@ -1548,7 +1548,7 @@ static u64 numa_get_avg_runtime(struct task_struct *p, u64 *period)
>                 *period = now - p->last_task_numa_placement;
>         } else {
>                 delta = p->se.avg.runnable_avg_sum;
> -               *period = p->se.avg.runnable_avg_period;
> +               *period = p->se.avg.avg_period;
>         }
> 
>         p->last_sum_exec_runtime = runtime;