2022-05-24 05:22:29

by Bing Huang

Subject: [PATCH] sche/fair: static cpumasks for load balance

The both cpu mask load_balance_mask and select_idle_mask just only used
in fair.c, but allocation in core.c in CONFIG_CPUMASK_OFFSTACK=y case,
and global via declare per cpu variations. More or less, it looks wired.

Signed-off-by: Bing Huang <[email protected]>
---
kernel/sched/core.c | 13 +++----------
kernel/sched/fair.c | 18 ++++++++++++++++--
kernel/sched/sched.h | 4 ++++
3 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index d58c0389eb23..64934c5e236d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9448,9 +9448,6 @@ LIST_HEAD(task_groups);
static struct kmem_cache *task_group_cache __read_mostly;
#endif

-DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
-DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
-
void __init sched_init(void)
{
unsigned long ptr = 0;
@@ -9494,14 +9491,10 @@ void __init sched_init(void)

#endif /* CONFIG_RT_GROUP_SCHED */
}
+
#ifdef CONFIG_CPUMASK_OFFSTACK
- for_each_possible_cpu(i) {
- per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
- cpumask_size(), GFP_KERNEL, cpu_to_node(i));
- per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
- cpumask_size(), GFP_KERNEL, cpu_to_node(i));
- }
-#endif /* CONFIG_CPUMASK_OFFSTACK */
+ init_working_cpumask();
+#endif

init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index a68482d66535..3a4b0dd1beb5 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5831,8 +5831,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
#ifdef CONFIG_SMP

/* Working cpumask for: load_balance, load_balance_newidle. */
-DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
-DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
+static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
+static DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);

#ifdef CONFIG_NO_HZ_COMMON

@@ -7052,6 +7052,20 @@ balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
}
#endif /* CONFIG_SMP */

+#ifdef CONFIG_CPUMASK_OFFSTACK
+void __init init_working_cpumask(void)
+{
+ int i;
+
+ for_each_possible_cpu(i) {
+ per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
+ cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+ per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
+ cpumask_size(), GFP_KERNEL, cpu_to_node(i));
+ }
+}
+#endif
+
static unsigned long wakeup_gran(struct sched_entity *se)
{
unsigned long gran = sysctl_sched_wakeup_granularity;
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 8dccb34eb190..9065be3def51 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -3087,4 +3087,8 @@ extern int sched_dynamic_mode(const char *str);
extern void sched_dynamic_update(int mode);
#endif

+#ifdef CONFIG_CPUMASK_OFFSTACK
+extern void __init init_working_cpumask(void);
+#endif /* CONFIG_CPUMASK_OFFSTACK */
+
#endif /* _KERNEL_SCHED_SCHED_H */
--
2.25.1


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2022-05-25 19:38:45

by Peter Zijlstra

Subject: Re: [PATCH] sche/fair: static cpumasks for load balance

On Mon, May 23, 2022 at 05:42:16PM +0800, Bing Huang wrote:
> The both cpu mask load_balance_mask and select_idle_mask just only used
> in fair.c, but allocation in core.c in CONFIG_CPUMASK_OFFSTACK=y case,
> and global via declare per cpu variations. More or less, it looks wired.
>
> Signed-off-by: Bing Huang <[email protected]>
> ---
> kernel/sched/core.c | 13 +++----------
> kernel/sched/fair.c | 18 ++++++++++++++++--
> kernel/sched/sched.h | 4 ++++
> 3 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d58c0389eb23..64934c5e236d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -9448,9 +9448,6 @@ LIST_HEAD(task_groups);
> static struct kmem_cache *task_group_cache __read_mostly;
> #endif
>
> -DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
> -DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
> -
> void __init sched_init(void)
> {
> unsigned long ptr = 0;
> @@ -9494,14 +9491,10 @@ void __init sched_init(void)
>
> #endif /* CONFIG_RT_GROUP_SCHED */
> }
> +
> #ifdef CONFIG_CPUMASK_OFFSTACK
> - for_each_possible_cpu(i) {
> - per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
> - cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> - per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
> - cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> - }
> -#endif /* CONFIG_CPUMASK_OFFSTACK */
> + init_working_cpumask();
> +#endif

We already have init_sched_fair_class(), can't you use that?

>
> init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a68482d66535..3a4b0dd1beb5 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5831,8 +5831,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
> #ifdef CONFIG_SMP
>
> /* Working cpumask for: load_balance, load_balance_newidle. */
> -DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
> -DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
> +static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
> +static DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
>
> #ifdef CONFIG_NO_HZ_COMMON
>
> @@ -7052,6 +7052,20 @@ balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
> }
> #endif /* CONFIG_SMP */
>
> +#ifdef CONFIG_CPUMASK_OFFSTACK
> +void __init init_working_cpumask(void)
> +{
> + int i;
> +
> + for_each_possible_cpu(i) {
> + per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
> + cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> + per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
> + cpumask_size(), GFP_KERNEL, cpu_to_node(i));
> + }
> +}
> +#endif

If you stick that #ifdef inside the function, you can remove it
everwhere else. Less #ifdef is more better.

2022-05-27 12:18:27

by Bing Huang

Subject: Re: [PATCH] sche/fair: static cpumasks for load balance

On 5/26/22 01:04, Peter Zijlstra wrote:
> On Mon, May 23, 2022 at 05:42:16PM +0800, Bing Huang wrote:
>> The both cpu mask load_balance_mask and select_idle_mask just only used
>> in fair.c, but allocation in core.c in CONFIG_CPUMASK_OFFSTACK=y case,
>> and global via declare per cpu variations. More or less, it looks wired.
>>
>> Signed-off-by: Bing Huang <[email protected]>
>> ---
>> kernel/sched/core.c | 13 +++----------
>> kernel/sched/fair.c | 18 ++++++++++++++++--
>> kernel/sched/sched.h | 4 ++++
>> 3 files changed, 23 insertions(+), 12 deletions(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index d58c0389eb23..64934c5e236d 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -9448,9 +9448,6 @@ LIST_HEAD(task_groups);
>> static struct kmem_cache *task_group_cache __read_mostly;
>> #endif
>>
>> -DECLARE_PER_CPU(cpumask_var_t, load_balance_mask);
>> -DECLARE_PER_CPU(cpumask_var_t, select_idle_mask);
>> -
>> void __init sched_init(void)
>> {
>> unsigned long ptr = 0;
>> @@ -9494,14 +9491,10 @@ void __init sched_init(void)
>>
>> #endif /* CONFIG_RT_GROUP_SCHED */
>> }
>> +
>> #ifdef CONFIG_CPUMASK_OFFSTACK
>> - for_each_possible_cpu(i) {
>> - per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
>> - cpumask_size(), GFP_KERNEL, cpu_to_node(i));
>> - per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
>> - cpumask_size(), GFP_KERNEL, cpu_to_node(i));
>> - }
>> -#endif /* CONFIG_CPUMASK_OFFSTACK */
>> + init_working_cpumask();
>> +#endif
> We already have init_sched_fair_class(), can't you use that?

OK, thanks for your review. I got it.

In addition, I notice that load_balance_mask and select_idle_mask are
defined
in CONFIG_SMP=y case in fair.c, so could be they moved inside
CONFIG_SMP, or just outside ?

>
>>
>> init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index a68482d66535..3a4b0dd1beb5 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -5831,8 +5831,8 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>> #ifdef CONFIG_SMP
>>
>> /* Working cpumask for: load_balance, load_balance_newidle. */
>> -DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
>> -DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
>> +static DEFINE_PER_CPU(cpumask_var_t, load_balance_mask);
>> +static DEFINE_PER_CPU(cpumask_var_t, select_idle_mask);
>>
>> #ifdef CONFIG_NO_HZ_COMMON
>>
>> @@ -7052,6 +7052,20 @@ balance_fair(struct rq *rq, struct task_struct *prev, struct rq_flags *rf)
>> }
>> #endif /* CONFIG_SMP */
>>
>> +#ifdef CONFIG_CPUMASK_OFFSTACK
>> +void __init init_working_cpumask(void)
>> +{
>> + int i;
>> +
>> + for_each_possible_cpu(i) {
>> + per_cpu(load_balance_mask, i) = (cpumask_var_t)kzalloc_node(
>> + cpumask_size(), GFP_KERNEL, cpu_to_node(i));
>> + per_cpu(select_idle_mask, i) = (cpumask_var_t)kzalloc_node(
>> + cpumask_size(), GFP_KERNEL, cpu_to_node(i));
>> + }
>> +}
>> +#endif
> If you stick that #ifdef inside the function, you can remove it
> everwhere else. Less #ifdef is more better.
I will remove it, move them inside init_sched_fair_class().