2022-06-02 07:49:58

by Bing Huang

Subject: [PATCH v3] sched/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.

Co-developed-by: Dietmar Eggemann <[email protected]>
Signed-off-by: Bing Huang <[email protected]>
---

v1->v2:
move load_balance_mask and select_idle_mask allocation from
sched_init() to init_sched_fair_class()
v2->v3:
fixup by Marco Elver <[email protected]>

kernel/sched/core.c | 11 -----------
kernel/sched/fair.c | 13 +++++++++++--
2 files changed, 11 insertions(+), 13 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 696c6490bd5b..707df2aeebf8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -9503,9 +9503,6 @@ 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;
@@ -9549,14 +9546,6 @@ 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_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime());

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 8c5b74f66bd3..310b6f52a7df 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5843,8 +5843,8 @@ 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

@@ -11841,6 +11841,15 @@ void show_numa_stats(struct task_struct *p, struct seq_file *m)
__init void init_sched_fair_class(void)
{
#ifdef CONFIG_SMP
+ int i;
+
+ for_each_possible_cpu(i) {
+ zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i),
+ GFP_KERNEL, cpu_to_node(i));
+ zalloc_cpumask_var_node(&per_cpu(select_idle_mask, i),
+ GFP_KERNEL, cpu_to_node(i));
+ }
+
open_softirq(SCHED_SOFTIRQ, run_rebalance_domains);

#ifdef CONFIG_NO_HZ_COMMON
--
2.25.1


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2022-06-08 01:29:01

by Dietmar Eggemann

Subject: Re: [PATCH v3] sched/fair: static cpumasks for load balance

On 02/06/2022 05:01, 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.

Maybe you can change this into:

sched/fair: Make per-cpu cpumasks static

load_balance_mask and select_idle_mask are only used in fair.c. Make
them static and move their allocation into init_sched_fair_class().

Replace kzalloc_node() with zalloc_cpumask_var_node() to get rid of the
CONFIG_CPUMASK_OFFSTACK #ifdef and to align with per-cpu cpumask
allocation for RT (local_cpu_mask in init_sched_rt_class()) and DL
class (local_cpu_mask_dl in init_sched_dl_class()).

> Co-developed-by: Dietmar Eggemann <[email protected]>

You can remove the `Co-developed-by`. I was just reviewing the patch and
gave suggestions.

[...]

> @@ -11841,6 +11841,15 @@ void show_numa_stats(struct task_struct *p, struct seq_file *m)
> __init void init_sched_fair_class(void)
> {
> #ifdef CONFIG_SMP
> + int i;
> +
> + for_each_possible_cpu(i) {
> + zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i),
> + GFP_KERNEL, cpu_to_node(i));
> + zalloc_cpumask_var_node(&per_cpu(select_idle_mask, i),
> + GFP_KERNEL, cpu_to_node(i));

@@ -11815,9 +11815,9 @@ __init void init_sched_fair_class(void)

for_each_possible_cpu(i) {
zalloc_cpumask_var_node(&per_cpu(load_balance_mask, i),
- GFP_KERNEL, cpu_to_node(i));
+ GFP_KERNEL, cpu_to_node(i));
zalloc_cpumask_var_node(&per_cpu(select_idle_mask, i),
- GFP_KERNEL, cpu_to_node(i));
+ GFP_KERNEL, cpu_to_node(i));
}

[...]

Reviewed-by: Dietmar Eggemann <[email protected]>