While investigating the sparse warning reported by the LKP bot [1],
observed that we have a redundant variable "top" in the function
build_sched_domains that was introduced in the recent commit
e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when
SD_NUMA spans multiple LLCs")
The existing variable "sd" suffices which allows us to remove the
redundant variable "top" while annotating the other variable "top_p"
with the "__rcu" annotation to silence the sparse warning.
[1] https://lore.kernel.org/lkml/[email protected]/
Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: K Prateek Nayak <[email protected]>
---
kernel/sched/topology.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index e6cd55951304..4b757fb8f661 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
(child->flags & SD_SHARE_PKG_RESOURCES)) {
- struct sched_domain *top, *top_p;
+ struct sched_domain __rcu *top_p;
unsigned int nr_llcs;
/*
@@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
sd->imb_numa_nr = imb;
/* Set span based on the first NUMA domain. */
- top = sd;
- top_p = top->parent;
+ top_p = sd->parent;
while (top_p && !(top_p->flags & SD_NUMA)) {
- top = top->parent;
- top_p = top->parent;
+ top_p = top_p->parent;
}
imb_span = top_p ? top_p->span_weight : sd->span_weight;
} else {
--
2.25.1
On Fri, Mar 04, 2022 at 12:56:44PM +0000, Valentin Schneider wrote:
> On 18/02/22 21:57, K Prateek Nayak wrote:
> > While investigating the sparse warning reported by the LKP bot [1],
> > observed that we have a redundant variable "top" in the function
> > build_sched_domains that was introduced in the recent commit
> > e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when
> > SD_NUMA spans multiple LLCs")
> >
> > The existing variable "sd" suffices which allows us to remove the
> > redundant variable "top" while annotating the other variable "top_p"
> > with the "__rcu" annotation to silence the sparse warning.
> >
> > [1] https://lore.kernel.org/lkml/[email protected]/
> >
> > Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
> > Reported-by: kernel test robot <[email protected]>
> > Signed-off-by: K Prateek Nayak <[email protected]>
> > ---
> > kernel/sched/topology.c | 8 +++-----
> > 1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> > index e6cd55951304..4b757fb8f661 100644
> > --- a/kernel/sched/topology.c
> > +++ b/kernel/sched/topology.c
> > @@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
> >
> > if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
> > (child->flags & SD_SHARE_PKG_RESOURCES)) {
> > - struct sched_domain *top, *top_p;
> > + struct sched_domain __rcu *top_p;
> > unsigned int nr_llcs;
> >
> > /*
> > @@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
> > sd->imb_numa_nr = imb;
> >
> > /* Set span based on the first NUMA domain. */
> > - top = sd;
> > - top_p = top->parent;
> > + top_p = sd->parent;
> > while (top_p && !(top_p->flags & SD_NUMA)) {
> > - top = top->parent;
> > - top_p = top->parent;
> > + top_p = top_p->parent;
> > }
> > imb_span = top_p ? top_p->span_weight : sd->span_weight;
>
>
> So sd starts as the first domain without SD_SHARE_PKG_RESOURCES (but its
> direct child has it), and the loop searches upward for a NUMA domain. This
> indeed shouldn't require two variables.
>
> I was going to say that while you're at it, you could init top_p to sd
> rather than sd->parent in case someone runs a non-default
> sched_domain_topology[], but NODE should have neither
> SD_SHARE_PKG_RESOURCES nor SD_NUMA, so that doesn't seem required.
>
> Reviewed-by: Valentin Schneider <[email protected]>
Thanks!
Hello everyone,
Ping :)
On 2/18/2022 9:57 PM, K Prateek Nayak wrote:
> While investigating the sparse warning reported by the LKP bot [1],
> observed that we have a redundant variable "top" in the function
> build_sched_domains that was introduced in the recent commit
> e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when
> SD_NUMA spans multiple LLCs")
>
> The existing variable "sd" suffices which allows us to remove the
> redundant variable "top" while annotating the other variable "top_p"
> with the "__rcu" annotation to silence the sparse warning.
>
> [1] https://lore.kernel.org/lkml/[email protected]/
>
> Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: K Prateek Nayak <[email protected]>
> ---
> kernel/sched/topology.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index e6cd55951304..4b757fb8f661 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
>
> if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
> (child->flags & SD_SHARE_PKG_RESOURCES)) {
> - struct sched_domain *top, *top_p;
> + struct sched_domain __rcu *top_p;
> unsigned int nr_llcs;
>
> /*
> @@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
> sd->imb_numa_nr = imb;
>
> /* Set span based on the first NUMA domain. */
> - top = sd;
> - top_p = top->parent;
> + top_p = sd->parent;
> while (top_p && !(top_p->flags & SD_NUMA)) {
> - top = top->parent;
> - top_p = top->parent;
> + top_p = top_p->parent;
> }
> imb_span = top_p ? top_p->span_weight : sd->span_weight;
> } else {
--
Thanks and Regards,
Prateek
On 18/02/22 21:57, K Prateek Nayak wrote:
> While investigating the sparse warning reported by the LKP bot [1],
> observed that we have a redundant variable "top" in the function
> build_sched_domains that was introduced in the recent commit
> e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when
> SD_NUMA spans multiple LLCs")
>
> The existing variable "sd" suffices which allows us to remove the
> redundant variable "top" while annotating the other variable "top_p"
> with the "__rcu" annotation to silence the sparse warning.
>
> [1] https://lore.kernel.org/lkml/[email protected]/
>
> Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
> Reported-by: kernel test robot <[email protected]>
> Signed-off-by: K Prateek Nayak <[email protected]>
> ---
> kernel/sched/topology.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index e6cd55951304..4b757fb8f661 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -2255,7 +2255,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
>
> if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
> (child->flags & SD_SHARE_PKG_RESOURCES)) {
> - struct sched_domain *top, *top_p;
> + struct sched_domain __rcu *top_p;
> unsigned int nr_llcs;
>
> /*
> @@ -2280,11 +2280,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
> sd->imb_numa_nr = imb;
>
> /* Set span based on the first NUMA domain. */
> - top = sd;
> - top_p = top->parent;
> + top_p = sd->parent;
> while (top_p && !(top_p->flags & SD_NUMA)) {
> - top = top->parent;
> - top_p = top->parent;
> + top_p = top_p->parent;
> }
> imb_span = top_p ? top_p->span_weight : sd->span_weight;
So sd starts as the first domain without SD_SHARE_PKG_RESOURCES (but its
direct child has it), and the loop searches upward for a NUMA domain. This
indeed shouldn't require two variables.
I was going to say that while you're at it, you could init top_p to sd
rather than sd->parent in case someone runs a non-default
sched_domain_topology[], but NODE should have neither
SD_SHARE_PKG_RESOURCES nor SD_NUMA, so that doesn't seem required.
Reviewed-by: Valentin Schneider <[email protected]>
> } else {
> --
> 2.25.1
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 7f434dff76215af00c26ba6449eaa4738fe9e2ab
Gitweb: https://git.kernel.org/tip/7f434dff76215af00c26ba6449eaa4738fe9e2ab
Author: K Prateek Nayak <[email protected]>
AuthorDate: Fri, 18 Feb 2022 21:57:43 +05:30
Committer: Peter Zijlstra <[email protected]>
CommitterDate: Tue, 08 Mar 2022 16:08:40 +01:00
sched/topology: Remove redundant variable and fix incorrect type in build_sched_domains
While investigating the sparse warning reported by the LKP bot [1],
observed that we have a redundant variable "top" in the function
build_sched_domains that was introduced in the recent commit
e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when
SD_NUMA spans multiple LLCs")
The existing variable "sd" suffices which allows us to remove the
redundant variable "top" while annotating the other variable "top_p"
with the "__rcu" annotation to silence the sparse warning.
[1] https://lore.kernel.org/lkml/[email protected]/
Fixes: e496132ebedd ("sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans multiple LLCs")
Reported-by: kernel test robot <[email protected]>
Signed-off-by: K Prateek Nayak <[email protected]>
Signed-off-by: Peter Zijlstra (Intel) <[email protected]>
Reviewed-by: Valentin Schneider <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/sched/topology.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 32841c6..43f2899 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2291,7 +2291,7 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
if (!(sd->flags & SD_SHARE_PKG_RESOURCES) && child &&
(child->flags & SD_SHARE_PKG_RESOURCES)) {
- struct sched_domain *top, *top_p;
+ struct sched_domain __rcu *top_p;
unsigned int nr_llcs;
/*
@@ -2316,11 +2316,9 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att
sd->imb_numa_nr = imb;
/* Set span based on the first NUMA domain. */
- top = sd;
- top_p = top->parent;
+ top_p = sd->parent;
while (top_p && !(top_p->flags & SD_NUMA)) {
- top = top->parent;
- top_p = top->parent;
+ top_p = top_p->parent;
}
imb_span = top_p ? top_p->span_weight : sd->span_weight;
} else {