Re: [RFC][PATCH 12/22] sched: add runtime reporting for -deadline tasks

[Peter Zijlstra <peterz@infradead.org>]

On Fri, 2010-10-29 at 08:36 +0200, Raistlin wrote:
> Make it available for the user-space the total amount of runtime
> time it has used from since it became a -deadline task.
> 
> This is something that is typically useful for monitoring from
> user-space the task CPU usage, and maybe implementing at that level
> some more sophisticated scheduling behaviour.
> 
> One example is feedback scheduling, where you try to adapt the
> scheduling parameters of a task by looking at its behaviour in
> a certain interval of time, applying concepts coming from control
> engineering.
> 
> Signed-off-by: Dario Faggioli <raistlin@linux.it>
> ---
>  include/linux/sched.h |    7 +++----
>  kernel/sched.c        |    3 +++
>  kernel/sched_debug.c  |    1 +
>  kernel/sched_dl.c     |    1 +
>  4 files changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/sched.h b/include/linux/sched.h
> index 8ae947b..b6f0635 100644
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -1242,14 +1242,15 @@ struct sched_rt_entity {
>  #endif
>  };
>  
> -#ifdef CONFIG_SCHEDSTATS
>  struct sched_stats_dl {
> +#ifdef CONFIG_SCHEDSTATS
>  	u64			last_dmiss;
>  	u64			last_rorun;
>  	u64			dmiss_max;
>  	u64			rorun_max;
> -};
>  #endif
> +	u64			tot_rtime;
> +};
>  

I know we agreed to pull this from the sched_param2 structure and delay
exposing this information for a while until the base patches got merged
and came up with a solid use-case, but reading this patch makes me
wonder why tsk->se.sum_exec_runtime isn't good enough?