diff mbox series

[3/3] sched/fair: fix unnecessary increase of balance interval

Message ID 1533657387-29039-4-git-send-email-vincent.guittot@linaro.org
State Superseded
Headers show
Series sched/fair: some fixes for asym_packing | expand

Commit Message

Vincent Guittot Aug. 7, 2018, 3:56 p.m. UTC 
In case of active balance, we increase the balance interval to cover
pinned tasks cases not covered by all_pinned logic. Neverthless, the active
migration triggered by asym packing should be treated as the normal
unbalanced case and reset the interval to default value otherwise active
migration for asym_packing can be easily delayed for hundreds of ms
because of this all_pinned detection mecanism.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>

---
 kernel/sched/fair.c | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

-- 
2.7.4

Comments

Peter Zijlstra Dec. 13, 2018, 1:52 p.m. UTC | #1 
On Tue, Aug 07, 2018 at 05:56:27PM +0200, Vincent Guittot wrote:
> +static inline bool

> +asym_active_balance(enum cpu_idle_type idle, unsigned int flags, int dst, int src)

>  {

> +	if (idle != CPU_NOT_IDLE) {

>  

>  		/*

>  		 * ASYM_PACKING needs to force migrate tasks from busy but

>  		 * lower priority CPUs in order to pack all tasks in the

>  		 * highest priority CPUs.

>  		 */

> +		if ((flags & SD_ASYM_PACKING) &&

> +		    sched_asym_prefer(dst, src))

> +			return true;

>  	}

>  

> +	return false;

> +}

> +

> +static int need_active_balance(struct lb_env *env)

> +{

> +	struct sched_domain *sd = env->sd;

> +

> +

> +	if (asym_active_balance(env->idle, sd->flags, env->dst_cpu, env->src_cpu))

> +		return 1;

> +

>  	/*

>  	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.

>  	 * It's worth migrating the task if the src_cpu's capacity is reduced

> @@ -8650,7 +8660,8 @@ static int load_balance(int this_cpu, struct rq *this_rq,

>  	} else

>  		sd->nr_balance_failed = 0;

>  

> +	if (likely(!active_balance) ||

> +	    asym_active_balance(env.idle, sd->flags, env.dst_cpu, env.src_cpu)) {


Perhaps like the below?

--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8857,21 +8857,24 @@ static struct rq *find_busiest_queue(str
  */
 #define MAX_PINNED_INTERVAL	512
 
+static inline bool
+asym_active_balance(struct lb_env *env)
+{
+	/*
+	 * ASYM_PACKING needs to force migrate tasks from busy but
+	 * lower priority CPUs in order to pack all tasks in the
+	 * highest priority CPUs.
+	 */
+	return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&
+		sched_asym_prefer(env->dst_cpu, env->src_cpu);
+}
+
 static int need_active_balance(struct lb_env *env)
 {
 	struct sched_domain *sd = env->sd;
 
-	if (env->idle != CPU_NOT_IDLE) {
-
-		/*
-		 * ASYM_PACKING needs to force migrate tasks from busy but
-		 * lower priority CPUs in order to pack all tasks in the
-		 * highest priority CPUs.
-		 */
-		if ((sd->flags & SD_ASYM_PACKING) &&
-		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
-			return 1;
-	}
+	if (asym_active_balance(env))
+		return 1;
 
 	/*
 	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
@@ -9150,7 +9153,7 @@ static int load_balance(int this_cpu, st
 	} else
 		sd->nr_balance_failed = 0;
 
-	if (likely(!active_balance)) {
+	if (likely(!active_balance) || asym_active_balance(&env)) {
 		/* We were unbalanced, so reset the balancing interval */
 		sd->balance_interval = sd->min_interval;
 	} else {
Vincent Guittot Dec. 13, 2018, 3:36 p.m. UTC | #2 
On Thu, 13 Dec 2018 at 14:52, Peter Zijlstra <peterz@infradead.org> wrote:
>

> On Tue, Aug 07, 2018 at 05:56:27PM +0200, Vincent Guittot wrote:

> > +static inline bool

> > +asym_active_balance(enum cpu_idle_type idle, unsigned int flags, int dst, int src)

> >  {

> > +     if (idle != CPU_NOT_IDLE) {

> >

> >               /*

> >                * ASYM_PACKING needs to force migrate tasks from busy but

> >                * lower priority CPUs in order to pack all tasks in the

> >                * highest priority CPUs.

> >                */

> > +             if ((flags & SD_ASYM_PACKING) &&

> > +                 sched_asym_prefer(dst, src))

> > +                     return true;

> >       }

> >

> > +     return false;

> > +}

> > +

> > +static int need_active_balance(struct lb_env *env)

> > +{

> > +     struct sched_domain *sd = env->sd;

> > +

> > +

> > +     if (asym_active_balance(env->idle, sd->flags, env->dst_cpu, env->src_cpu))

> > +             return 1;

> > +

> >       /*

> >        * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.

> >        * It's worth migrating the task if the src_cpu's capacity is reduced

> > @@ -8650,7 +8660,8 @@ static int load_balance(int this_cpu, struct rq *this_rq,

> >       } else

> >               sd->nr_balance_failed = 0;

> >

> > +     if (likely(!active_balance) ||

> > +         asym_active_balance(env.idle, sd->flags, env.dst_cpu, env.src_cpu)) {

>

> Perhaps like the below?


Yes. Far more simple and readable

>

> --- a/kernel/sched/fair.c

> +++ b/kernel/sched/fair.c

> @@ -8857,21 +8857,24 @@ static struct rq *find_busiest_queue(str

>   */

>  #define MAX_PINNED_INTERVAL    512

>

> +static inline bool

> +asym_active_balance(struct lb_env *env)

> +{

> +       /*

> +        * ASYM_PACKING needs to force migrate tasks from busy but

> +        * lower priority CPUs in order to pack all tasks in the

> +        * highest priority CPUs.

> +        */

> +       return env->idle != CPU_NOT_IDLE && (env->sd->flags & SD_ASYM_PACKING) &&

> +               sched_asym_prefer(env->dst_cpu, env->src_cpu);

> +}

> +

>  static int need_active_balance(struct lb_env *env)

>  {

>         struct sched_domain *sd = env->sd;

>

> -       if (env->idle != CPU_NOT_IDLE) {

> -

> -               /*

> -                * ASYM_PACKING needs to force migrate tasks from busy but

> -                * lower priority CPUs in order to pack all tasks in the

> -                * highest priority CPUs.

> -                */

> -               if ((sd->flags & SD_ASYM_PACKING) &&

> -                   sched_asym_prefer(env->dst_cpu, env->src_cpu))

> -                       return 1;

> -       }

> +       if (asym_active_balance(env))

> +               return 1;

>

>         /*

>          * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.

> @@ -9150,7 +9153,7 @@ static int load_balance(int this_cpu, st

>         } else

>                 sd->nr_balance_failed = 0;

>

> -       if (likely(!active_balance)) {

> +       if (likely(!active_balance) || asym_active_balance(&env)) {

>                 /* We were unbalanced, so reset the balancing interval */

>                 sd->balance_interval = sd->min_interval;

>         } else {
diff mbox series

Patch

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5f1b6c6..ceb6bed 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8360,22 +8360,32 @@  static struct rq *find_busiest_queue(struct lb_env *env,
  */
 #define MAX_PINNED_INTERVAL	512
 
-static int need_active_balance(struct lb_env *env)
+static inline bool
+asym_active_balance(enum cpu_idle_type idle, unsigned int flags, int dst, int src)
 {
-	struct sched_domain *sd = env->sd;
-
-	if (env->idle != CPU_NOT_IDLE) {
+	if (idle != CPU_NOT_IDLE) {
 
 		/*
 		 * ASYM_PACKING needs to force migrate tasks from busy but
 		 * lower priority CPUs in order to pack all tasks in the
 		 * highest priority CPUs.
 		 */
-		if ((sd->flags & SD_ASYM_PACKING) &&
-		    sched_asym_prefer(env->dst_cpu, env->src_cpu))
-			return 1;
+		if ((flags & SD_ASYM_PACKING) &&
+		    sched_asym_prefer(dst, src))
+			return true;
 	}
 
+	return false;
+}
+
+static int need_active_balance(struct lb_env *env)
+{
+	struct sched_domain *sd = env->sd;
+
+
+	if (asym_active_balance(env->idle, sd->flags, env->dst_cpu, env->src_cpu))
+		return 1;
+
 	/*
 	 * The dst_cpu is idle and the src_cpu CPU has only 1 CFS task.
 	 * It's worth migrating the task if the src_cpu's capacity is reduced
@@ -8650,7 +8660,8 @@  static int load_balance(int this_cpu, struct rq *this_rq,
 	} else
 		sd->nr_balance_failed = 0;
 
-	if (likely(!active_balance)) {
+	if (likely(!active_balance) ||
+	    asym_active_balance(env.idle, sd->flags, env.dst_cpu, env.src_cpu)) {
 		/* We were unbalanced, so reset the balancing interval */
 		sd->balance_interval = sd->min_interval;
 	} else {