2014-12-05 06:22:41

by Zhang, Jun

Subject: [PATCH] sched/fair: fix find_idlest_cpu return -1

From: zhang jun <[email protected]>

find_idlest_cpu return -1 is not reasonable, set default value to this_cpu.

Signed-off-by: zhang jun <[email protected]>
Signed-off-by: Chuansheng Liu <[email protected]>
Signed-off-by: Changcheng Liu <[email protected]>
Cc: Hillf Danton <[email protected]>
Cc: Vincent Guittot <[email protected]>
Cc: <[email protected]> # 3.14.25
---
kernel/sched/fair.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9b4c4f3..9d18887 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -4151,7 +4151,7 @@ static int
find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
{
unsigned long load, min_load = ULONG_MAX;
- int idlest = -1;
+ int idlest = this_cpu;
int i;

/* Traverse only the allowed CPUs */
@@ -4284,7 +4284,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
}

new_cpu = find_idlest_cpu(group, p, cpu);
- if (new_cpu == -1 || new_cpu == cpu) {
+ if (new_cpu == cpu) {
/* Now try balancing at a lower domain level of cpu */
sd = sd->child;
continue;
--
1.7.9.5

2014-12-05 06:38:57

by Hillf Danton

Subject: Re: [PATCH] sched/fair: fix find_idlest_cpu return -1

Cc: [email protected]
>
> From: zhang jun <[email protected]>
>
> find_idlest_cpu return -1 is not reasonable, set default value to this_cpu.
>
> Signed-off-by: zhang jun <[email protected]>
> Signed-off-by: Chuansheng Liu <[email protected]>
> Signed-off-by: Changcheng Liu <[email protected]>
> Cc: Hillf Danton <[email protected]>
> Cc: Vincent Guittot <[email protected]>
> Cc: <[email protected]> # 3.14.25
> ---
> kernel/sched/fair.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 9b4c4f3..9d18887 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4151,7 +4151,7 @@ static int
> find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu)
> {
> unsigned long load, min_load = ULONG_MAX;
> - int idlest = -1;
> + int idlest = this_cpu;
> int i;
>
> /* Traverse only the allowed CPUs */
> @@ -4284,7 +4284,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
> }
>
> new_cpu = find_idlest_cpu(group, p, cpu);
> - if (new_cpu == -1 || new_cpu == cpu) {
> + if (new_cpu == cpu) {
> /* Now try balancing at a lower domain level of cpu */
> sd = sd->child;
> continue;
> --
> 1.7.9.5

2014-12-15 16:59:27

by Peter Zijlstra

Subject: Re: [PATCH] sched/fair: fix find_idlest_cpu return -1

On Fri, Dec 05, 2014 at 01:58:01PM +0800, [email protected] wrote:
> From: zhang jun <[email protected]>
>
> find_idlest_cpu return -1 is not reasonable, set default value to this_cpu.

This fails to explain why.

> Signed-off-by: zhang jun <[email protected]>
> Signed-off-by: Chuansheng Liu <[email protected]>
> Signed-off-by: Changcheng Liu <[email protected]>

This is an invalid SoB chain.

> Cc: Hillf Danton <[email protected]>
> Cc: Vincent Guittot <[email protected]>
> Cc: <[email protected]> # 3.14.25