linux-kernel - Re: [PATCH v3 5/6] sched/fair: Rename scale_load() and scale_load

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Date:	Thu, 28 Apr 2016 13:18:00 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Yuyang Du <yuyang.du@...el.com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, bsegall@...gle.com, pjt@...gle.com,
	morten.rasmussen@....com, dietmar.eggemann@....com,
	lizefan@...wei.com, umgwanakikbuti@...il.com
Subject: Re: [PATCH v3 5/6] sched/fair: Rename scale_load() and
 scale_load_down()

Le Thursday 28 Apr 2016 à 11:19:19 (+0200), Peter Zijlstra a écrit :
> On Tue, Apr 05, 2016 at 12:12:30PM +0800, Yuyang Du wrote:
> > Rename scale_load() and scale_load_down() to user_to_kernel_load()
> > and kernel_to_user_load() respectively, to allow the names to bear
> > what they are really about.
> 
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -189,7 +189,7 @@ static void __update_inv_weight(struct load_weight *lw)
> >  	if (likely(lw->inv_weight))
> >  		return;
> >  
> > -	w = scale_load_down(lw->weight);
> > +	w = kernel_to_user_load(lw->weight);
> >  
> >  	if (BITS_PER_LONG > 32 && unlikely(w >= WMULT_CONST))
> >  		lw->inv_weight = 1;
> > @@ -213,7 +213,7 @@ static void __update_inv_weight(struct load_weight *lw)
> >   */
> >  static u64 __calc_delta(u64 delta_exec, unsigned long weight, struct load_weight *lw)
> >  {
> > -	u64 fact = scale_load_down(weight);
> > +	u64 fact = kernel_to_user_load(weight);
> >  	int shift = WMULT_SHIFT;
> >  
> >  	__update_inv_weight(lw);
> > @@ -6952,10 +6952,11 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
> >  	 */
> >  	if (busiest->group_type == group_overloaded &&
> >  	    local->group_type   == group_overloaded) {
> > +		unsigned long min_cpu_load =
> > +			kernel_to_user_load(NICE_0_LOAD) * busiest->group_capacity;
> >  		load_above_capacity = busiest->sum_nr_running * NICE_0_LOAD;
> > -		if (load_above_capacity > scale_load(busiest->group_capacity))
> > -			load_above_capacity -=
> > -				scale_load(busiest->group_capacity);
> > +		if (load_above_capacity > min_cpu_load)
> > +			load_above_capacity -= min_cpu_load;
> >  		else
> >  			load_above_capacity = ~0UL;
> >  	}
> 
> Except these 3 really are not about user/kernel visible fixed point
> ranges _at_all_... :/

While trying to optimize the calcultaion of min_cpu_load, i have broken evrything

it should be :

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0b6659d..3411eb7 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6953,7 +6953,7 @@ static inline void calculate_imbalance(struct lb_env *env, struct sd_lb_stats *s
 	if (busiest->group_type == group_overloaded &&
 	    local->group_type   == group_overloaded) {
 		unsigned long min_cpu_load =
-			kernel_to_user_load(NICE_0_LOAD) * busiest->group_capacity;
+			busiest->group_capacity * NICE_0_LOAD / SCHED_CAPACITY_SCALE;
 		load_above_capacity = busiest->sum_nr_running * NICE_0_LOAD;
 		if (load_above_capacity > min_cpu_load)
 			load_above_capacity -= min_cpu_load;


>
>