linux-kernel - Re: sched: per-entity load-tracking

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Date:	Mon, 08 Oct 2012 14:14:45 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Paul Turner <pjt@...gle.com>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>,
	Srivatsa Vaddagiri <vatsa@...ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Venki Pallipadi <venki@...gle.com>,
	Ben Segall <bsegall@...gle.com>,
	Mike Galbraith <efault@....de>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Nikunj A Dadhania <nikunj@...ux.vnet.ibm.com>,
	Morten Rasmussen <Morten.Rasmussen@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: sched: per-entity load-tracking

On Sat, 2012-10-06 at 09:39 +0200, Ingo Molnar wrote:

Thanks Ingo! Paul,

>  tip/kernel/sched/fair.c |   28 ++++++++++++++++++----------
>  1 file changed, 18 insertions(+), 10 deletions(-)
> 
> Index: tip/kernel/sched/fair.c
> ===================================================================
> --- tip.orig/kernel/sched/fair.c
> +++ tip/kernel/sched/fair.c
>  
> @@ -1151,7 +1156,7 @@ static inline void update_cfs_shares(str
>   * Note: The tables below are dependent on this value.
>   */
>  #define LOAD_AVG_PERIOD 32
> -#define LOAD_AVG_MAX 47765 /* maximum possible load avg */
> +#define LOAD_AVG_MAX 47742 /* maximum possible load avg */
>  #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_MAX_AVG */
>  
>  /* Precomputed fixed inverse multiplies for multiplication by y^n */
> @@ -1203,7 +1208,8 @@ static __always_inline u64 decay_load(u6
>  	}
>  
>  	val *= runnable_avg_yN_inv[local_n];
> -	return SRR(val, 32);
> +	/* We don't use SRR here since we always want to round down. */
> +	return val >> 32;
>  }
>  
>  /*

This is from patches/sched-fast_decay.patch and I changed both the
patch and the changelog to reflect your changes.


>@@ -262,6 +262,9 @@ static inline struct cfs_rq *group_cfs_r
>  	return grp->my_q;
>  }
>  
> +static void update_cfs_rq_blocked_load(struct cfs_rq *cfs_rq,
> +				       int force_update);
> +
>  static inline void list_add_leaf_cfs_rq(struct cfs_rq *cfs_rq)
>  {
>  	if (!cfs_rq->on_list) {
> @@ -281,6 +284,8 @@ static inline void list_add_leaf_cfs_rq(
>  		}
>  
>  		cfs_rq->on_list = 1;
> +		/* We should have no load, but we need to update last_decay. */
> +		update_cfs_rq_blocked_load(cfs_rq, 0);
>  	}
>  }


This seems to have come from patches/sched-cfs_rq_blocked_load.patch, and I merged
it in there. With subsequent updates in 
patches/sched-wakeup_load.patch. I didn't find any changes to the Changelogs for either.


> @@ -4236,13 +4242,15 @@ static void __update_blocked_averages_cp
>  	if (se) {
>  		update_entity_load_avg(se, 1);
>  		/*
> -		 * We can pivot on the runnable average decaying to zero for
> -		 * list removal since the parent average will always be >=
> -		 * child.
> +		 * We pivot on our runnable average having decayed to zero for
> +		 * list removal.  This generally implies that all our children
> +		 * have also been removed (modulo rounding error or bandwidth
> +		 * control); however, such cases are rare and we can fix these
> +		 * at enqueue.
> +		 *
> +		 * TODO: fix up out-of-order children on enqueue.
>  		 */
> -		if (se->avg.runnable_avg_sum)
> -			update_cfs_shares(cfs_rq);
> -		else
> +		if (!se->avg.runnable_avg_sum && !cfs_rq->nr_running)
>  			list_del_leaf_cfs_rq(cfs_rq);
>  	} else {
>  		struct rq *rq = rq_of(cfs_rq);


This hunk seems to have come from
patches/sched-swap_update_shares.patch, merged in there, no Changelog
changes afaict.


I've updated my queue (at the usual location:
http://programming.kicks-ass.net/sekrit/patches.tar.bz2), Paul please
verify I didn't miss anything.


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