When picking out a CPU on a task wakeup, select_idle_smt() has to take
into account the scheduling domain of @target. This is because the
"isolcpus" kernel command line option can remove CPUs from the domain to
isolate them from other SMT siblings.
This fix checks if the candidate CPU is in the target scheduling domain.
The commit df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated
domain") originally proposed this fix by adding the check of the scheduling
domain in the loop. However, the commit 3e6efe87cd5cc ("sched/fair: Remove
redundant check in select_idle_smt()") accidentally removed the check.
This commit brings the check back.
Fixes: 3e6efe87cd5c ("sched/fair: Remove redundant check in select_idle_smt()")
Signed-off-by: Keisuke Nishimura <[email protected]>
Signed-off-by: Julia Lawall <[email protected]>
---
v2: - Changed the log message to mention only isolcpus
- Moved the check in the loop according to the original fix
kernel/sched/fair.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 533547e3c90a..66457d4b8965 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
/*
* Scan the local SMT mask for idle CPUs.
*/
-static int select_idle_smt(struct task_struct *p, int target)
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
int cpu;
for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
if (cpu == target)
continue;
+ /*
+ * Check if the CPU is in the LLC scheduling domain of @target.
+ * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
+ */
+ if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
+ continue;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
return cpu;
}
@@ -7341,7 +7347,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma
return __select_idle_cpu(core, p);
}
-static inline int select_idle_smt(struct task_struct *p, int target)
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
return -1;
}
@@ -7591,7 +7597,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
has_idle_core = test_idle_cores(target);
if (!has_idle_core && cpus_share_cache(prev, target)) {
- i = select_idle_smt(p, prev);
+ i = select_idle_smt(p, sd, prev);
if ((unsigned int)i < nr_cpumask_bits)
return i;
}
--
2.34.1
When picking out a CPU on a task wakeup, select_idle_core() has to take
into account the scheduling domain where the function looks for the CPU.
This is because the "isolcpus" kernel command line option can remove CPUs
from the domain to isolate them from other SMT siblings.
This change replaces the set of CPUs allowed to run the task from
p->cpus_ptr by the intersection of p->cpus_ptr and sched_domain_span(sd)
which is stored in the cpus argument provided by select_idle_cpu.
Fixes: 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
Signed-off-by: Keisuke Nishimura <[email protected]>
Signed-off-by: Julia Lawall <[email protected]>
---
v2: - Changed the log message to mention only isolcpus
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 66457d4b8965..e2b4e0396af8 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7289,7 +7289,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
if (!available_idle_cpu(cpu)) {
idle = false;
if (*idle_cpu == -1) {
- if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
+ if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
*idle_cpu = cpu;
break;
}
@@ -7297,7 +7297,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
}
break;
}
- if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+ if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
*idle_cpu = cpu;
}
--
2.34.1
On Wed, 10 Jan 2024 at 14:19, Keisuke Nishimura
<[email protected]> wrote:
>
> When picking out a CPU on a task wakeup, select_idle_core() has to take
> into account the scheduling domain where the function looks for the CPU.
> This is because the "isolcpus" kernel command line option can remove CPUs
> from the domain to isolate them from other SMT siblings.
>
> This change replaces the set of CPUs allowed to run the task from
> p->cpus_ptr by the intersection of p->cpus_ptr and sched_domain_span(sd)
> which is stored in the cpus argument provided by select_idle_cpu.
>
> Fixes: 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
> Signed-off-by: Keisuke Nishimura <[email protected]>
> Signed-off-by: Julia Lawall <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
> ---
> v2: - Changed the log message to mention only isolcpus
>
> 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 66457d4b8965..e2b4e0396af8 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7289,7 +7289,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
> if (!available_idle_cpu(cpu)) {
> idle = false;
> if (*idle_cpu == -1) {
> - if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
> + if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
> *idle_cpu = cpu;
> break;
> }
> @@ -7297,7 +7297,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
> }
> break;
> }
> - if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
> + if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
> *idle_cpu = cpu;
> }
>
> --
> 2.34.1
>
On Wed, 10 Jan 2024 at 14:19, Keisuke Nishimura
<[email protected]> wrote:
>
> When picking out a CPU on a task wakeup, select_idle_smt() has to take
> into account the scheduling domain of @target. This is because the
> "isolcpus" kernel command line option can remove CPUs from the domain to
> isolate them from other SMT siblings.
>
> This fix checks if the candidate CPU is in the target scheduling domain.
>
> The commit df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated
> domain") originally proposed this fix by adding the check of the scheduling
> domain in the loop. However, the commit 3e6efe87cd5cc ("sched/fair: Remove
> redundant check in select_idle_smt()") accidentally removed the check.
> This commit brings the check back.
>
> Fixes: 3e6efe87cd5c ("sched/fair: Remove redundant check in select_idle_smt()")
> Signed-off-by: Keisuke Nishimura <[email protected]>
> Signed-off-by: Julia Lawall <[email protected]>
> ---
> v2: - Changed the log message to mention only isolcpus
> - Moved the check in the loop according to the original fix
>
> kernel/sched/fair.c | 12 +++++++++---
> 1 file changed, 9 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 533547e3c90a..66457d4b8965 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
> /*
> * Scan the local SMT mask for idle CPUs.
> */
> -static int select_idle_smt(struct task_struct *p, int target)
> +static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
> {
> int cpu;
>
> for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
> if (cpu == target)
> continue;
> + /*
> + * Check if the CPU is in the LLC scheduling domain of @target.
> + * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
> + */
> + if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
commit df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated domain")
also checked if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
Why didn't you also re-add this test ?
> + continue;
> if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
> return cpu;
> }
> @@ -7341,7 +7347,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma
> return __select_idle_cpu(core, p);
> }
>
> -static inline int select_idle_smt(struct task_struct *p, int target)
> +static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
> {
> return -1;
> }
> @@ -7591,7 +7597,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
> has_idle_core = test_idle_cores(target);
>
> if (!has_idle_core && cpus_share_cache(prev, target)) {
> - i = select_idle_smt(p, prev);
> + i = select_idle_smt(p, sd, prev);
> if ((unsigned int)i < nr_cpumask_bits)
> return i;
> }
> --
> 2.34.1
>
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 533547e3c90a..66457d4b8965 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
>> /*
>> * Scan the local SMT mask for idle CPUs.
>> */
>> -static int select_idle_smt(struct task_struct *p, int target)
>> +static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
>> {
>> int cpu;
>>
>> for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
>> if (cpu == target)
>> continue;
>> + /*
>> + * Check if the CPU is in the LLC scheduling domain of @target.
>> + * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
>> + */
>> + if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
>
> commit df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated domain")
> also checked if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
>
> Why didn't you also re-add this test ?
>
>
Thank you for your comment. This is because the iterator "for_each_cpu_and(cpu,
cpu_smt_mask(target), p->cpus_ptr)" ensures that cpu is included in p->cpus_ptr.
The iterator has changed. FYI, here is the change made in commit df3cb4ea1fb6:
for_each_cpu(cpu, cpu_smt_mask(target)) {
- if (!cpumask_test_cpu(cpu, p->cpus_ptr))
+ if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
+ !cpumask_test_cpu(cpu, sched_domain_span(sd)))
continue;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
best,
Keisuke
On Wed, 10 Jan 2024 at 18:57, Keisuke Nishimura
<[email protected]> wrote:
>
> >>
> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> >> index 533547e3c90a..66457d4b8965 100644
> >> --- a/kernel/sched/fair.c
> >> +++ b/kernel/sched/fair.c
> >> @@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
> >> /*
> >> * Scan the local SMT mask for idle CPUs.
> >> */
> >> -static int select_idle_smt(struct task_struct *p, int target)
> >> +static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
> >> {
> >> int cpu;
> >>
> >> for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
> >> if (cpu == target)
> >> continue;
> >> + /*
> >> + * Check if the CPU is in the LLC scheduling domain of @target.
> >> + * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
> >> + */
> >> + if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
> >
> > commit df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated domain")
> > also checked if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
> >
> > Why didn't you also re-add this test ?
> >
> >
>
> Thank you for your comment. This is because the iterator "for_each_cpu_and(cpu,
> cpu_smt_mask(target), p->cpus_ptr)" ensures that cpu is included in p->cpus_ptr.
Ah yes indeed. I didn't notice that it was now included in the for_each_cpu_and
Reviewed-by: Vincent Guittot <[email protected]>
>
> The iterator has changed. FYI, here is the change made in commit df3cb4ea1fb6:
>
> for_each_cpu(cpu, cpu_smt_mask(target)) {
> - if (!cpumask_test_cpu(cpu, p->cpus_ptr))
> + if (!cpumask_test_cpu(cpu, p->cpus_ptr) ||
> + !cpumask_test_cpu(cpu, sched_domain_span(sd)))
> continue;
> if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
>
> best,
> Keisuke
>
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 23d04d8c6b8ec339057264659b7834027f3e6a63
Gitweb: https://git.kernel.org/tip/23d04d8c6b8ec339057264659b7834027f3e6a63
Author: Keisuke Nishimura <[email protected]>
AuthorDate: Wed, 10 Jan 2024 14:17:07 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Wed, 28 Feb 2024 15:15:49 +01:00
sched/fair: Take the scheduling domain into account in select_idle_core()
When picking a CPU on task wakeup, select_idle_core() has to take
into account the scheduling domain where the function looks for the CPU.
This is because the "isolcpus" kernel command line option can remove CPUs
from the domain to isolate them from other SMT siblings.
This change replaces the set of CPUs allowed to run the task from
p->cpus_ptr by the intersection of p->cpus_ptr and sched_domain_span(sd)
which is stored in the 'cpus' argument provided by select_idle_cpu().
Fixes: 9fe1f127b913 ("sched/fair: Merge select_idle_core/cpu()")
Signed-off-by: Keisuke Nishimura <[email protected]>
Signed-off-by: Julia Lawall <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
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 005f6d3..352222d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7289,7 +7289,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
if (!available_idle_cpu(cpu)) {
idle = false;
if (*idle_cpu == -1) {
- if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, p->cpus_ptr)) {
+ if (sched_idle_cpu(cpu) && cpumask_test_cpu(cpu, cpus)) {
*idle_cpu = cpu;
break;
}
@@ -7297,7 +7297,7 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
}
break;
}
- if (*idle_cpu == -1 && cpumask_test_cpu(cpu, p->cpus_ptr))
+ if (*idle_cpu == -1 && cpumask_test_cpu(cpu, cpus))
*idle_cpu = cpu;
}
The following commit has been merged into the sched/core branch of tip:
Commit-ID: 8aeaffef8c6eceab0e1498486fdd4f3dc3b7066c
Gitweb: https://git.kernel.org/tip/8aeaffef8c6eceab0e1498486fdd4f3dc3b7066c
Author: Keisuke Nishimura <[email protected]>
AuthorDate: Wed, 10 Jan 2024 14:17:06 +01:00
Committer: Ingo Molnar <[email protected]>
CommitterDate: Wed, 28 Feb 2024 15:15:48 +01:00
sched/fair: Take the scheduling domain into account in select_idle_smt()
When picking a CPU on task wakeup, select_idle_smt() has to take
into account the scheduling domain of @target. This is because the
"isolcpus" kernel command line option can remove CPUs from the domain to
isolate them from other SMT siblings.
This fix checks if the candidate CPU is in the target scheduling domain.
Commit:
df3cb4ea1fb6 ("sched/fair: Fix wrong cpu selecting from isolated domain")
.. originally introduced this fix by adding the check of the scheduling
domain in the loop.
However, commit:
3e6efe87cd5cc ("sched/fair: Remove redundant check in select_idle_smt()")
.. accidentally removed the check. Bring it back.
Fixes: 3e6efe87cd5c ("sched/fair: Remove redundant check in select_idle_smt()")
Signed-off-by: Keisuke Nishimura <[email protected]>
Signed-off-by: Julia Lawall <[email protected]>
Signed-off-by: Ingo Molnar <[email protected]>
Reviewed-by: Vincent Guittot <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
---
kernel/sched/fair.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ba36339..005f6d3 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7311,13 +7311,19 @@ static int select_idle_core(struct task_struct *p, int core, struct cpumask *cpu
/*
* Scan the local SMT mask for idle CPUs.
*/
-static int select_idle_smt(struct task_struct *p, int target)
+static int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
int cpu;
for_each_cpu_and(cpu, cpu_smt_mask(target), p->cpus_ptr) {
if (cpu == target)
continue;
+ /*
+ * Check if the CPU is in the LLC scheduling domain of @target.
+ * Due to isolcpus, there is no guarantee that all the siblings are in the domain.
+ */
+ if (!cpumask_test_cpu(cpu, sched_domain_span(sd)))
+ continue;
if (available_idle_cpu(cpu) || sched_idle_cpu(cpu))
return cpu;
}
@@ -7341,7 +7347,7 @@ static inline int select_idle_core(struct task_struct *p, int core, struct cpuma
return __select_idle_cpu(core, p);
}
-static inline int select_idle_smt(struct task_struct *p, int target)
+static inline int select_idle_smt(struct task_struct *p, struct sched_domain *sd, int target)
{
return -1;
}
@@ -7591,7 +7597,7 @@ static int select_idle_sibling(struct task_struct *p, int prev, int target)
has_idle_core = test_idle_cores(target);
if (!has_idle_core && cpus_share_cache(prev, target)) {
- i = select_idle_smt(p, prev);
+ i = select_idle_smt(p, sd, prev);
if ((unsigned int)i < nr_cpumask_bits)
return i;
}