2021-04-26 17:05:38

by Gautham R Shenoy

Subject: [PATCH] sched/fair: Fix unsetting of "has_idle_cores" flag

From: "Gautham R. Shenoy" <[email protected]>

In commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()"), in
select_idle_cpu(), we check if an idle core is present in the LLC of the
target CPU via the flag "has_idle_cores". We look for the idle core in
select_idle_cores(). If select_idle_cores() isn't able to find an idle
core/CPU, we need to unset the has_idle_cores flag in the LLC of the
target to prevent other CPUs from going down this route.

However, the current code is unsetting it in the LLC of the current CPU
instead of the target CPU. This patch fixes this issue.

Fixes: Commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
Cc: Mel Gorman <[email protected]>
Signed-off-by: Gautham R. Shenoy <[email protected]>
---
kernel/sched/fair.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 794c2cb..5fb5020 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6171,7 +6171,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
}

if (smt)
- set_idle_cores(this, false);
+ set_idle_cores(target, false);

if (sched_feat(SIS_PROP) && !smt) {
time = cpu_clock(this) - time;
--
1.9.4

2021-04-27 07:11:16

by Vincent Guittot

Subject: Re: [PATCH] sched/fair: Fix unsetting of "has_idle_cores" flag

On Mon, 26 Apr 2021 at 19:04, Gautham R. Shenoy <[email protected]> wrote:
>
> From: "Gautham R. Shenoy" <[email protected]>
>
> In commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()"), in
> select_idle_cpu(), we check if an idle core is present in the LLC of the
> target CPU via the flag "has_idle_cores". We look for the idle core in
> select_idle_cores(). If select_idle_cores() isn't able to find an idle
> core/CPU, we need to unset the has_idle_cores flag in the LLC of the
> target to prevent other CPUs from going down this route.
>
> However, the current code is unsetting it in the LLC of the current CPU
> instead of the target CPU. This patch fixes this issue.
>
> Fixes: Commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
> Cc: Mel Gorman <[email protected]>
> Signed-off-by: Gautham R. Shenoy <[email protected]>

Reviewed-by: Vincent Guittot <[email protected]>

> ---
> kernel/sched/fair.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 794c2cb..5fb5020 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6171,7 +6171,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> }
>
> if (smt)
> - set_idle_cores(this, false);
> + set_idle_cores(target, false);
>
> if (sched_feat(SIS_PROP) && !smt) {
> time = cpu_clock(this) - time;
> --
> 1.9.4
>

2021-04-27 07:56:24

by Mel Gorman

Subject: Re: [PATCH] sched/fair: Fix unsetting of "has_idle_cores" flag

On Mon, Apr 26, 2021 at 10:34:12PM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <[email protected]>
>
> In commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()"), in
> select_idle_cpu(), we check if an idle core is present in the LLC of the
> target CPU via the flag "has_idle_cores". We look for the idle core in
> select_idle_cores(). If select_idle_cores() isn't able to find an idle
> core/CPU, we need to unset the has_idle_cores flag in the LLC of the
> target to prevent other CPUs from going down this route.
>
> However, the current code is unsetting it in the LLC of the current CPU
> instead of the target CPU. This patch fixes this issue.
>
> Fixes: Commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
> Cc: Mel Gorman <[email protected]>
> Signed-off-by: Gautham R. Shenoy <[email protected]>

Acked-by: Mel Gorman <[email protected]>

--
Mel Gorman
SUSE Labs

2021-05-10 16:09:22

by Gautham R Shenoy

Subject: Re: [PATCH] sched/fair: Fix unsetting of "has_idle_cores" flag

Peter, Ingo,

Pinging to check on this tiny fix :-)


On Mon, Apr 26, 2021 at 10:34:12PM +0530, Gautham R. Shenoy wrote:
> From: "Gautham R. Shenoy" <[email protected]>
>
> In commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()"), in
> select_idle_cpu(), we check if an idle core is present in the LLC of the
> target CPU via the flag "has_idle_cores". We look for the idle core in
> select_idle_cores(). If select_idle_cores() isn't able to find an idle
> core/CPU, we need to unset the has_idle_cores flag in the LLC of the
> target to prevent other CPUs from going down this route.
>
> However, the current code is unsetting it in the LLC of the current CPU
> instead of the target CPU. This patch fixes this issue.
>
> Fixes: Commit 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
> Cc: Mel Gorman <[email protected]>
> Signed-off-by: Gautham R. Shenoy <[email protected]>
> ---
> kernel/sched/fair.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 794c2cb..5fb5020 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -6171,7 +6171,7 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, int t
> }
>
> if (smt)
> - set_idle_cores(this, false);
> + set_idle_cores(target, false);
>
> if (sched_feat(SIS_PROP) && !smt) {
> time = cpu_clock(this) - time;
> --
> 1.9.4
>