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sched: Do not construct nor expose RT_GROUP_SCHED structures if disabled 

Thanks to kernel cmdline being available early, before any
cgroup hierarchy exists, we can achieve the RT_GROUP_SCHED boottime
disabling goal by simply skipping any creation (and destruction) of
RT_GROUP data and its exposure via RT attributes.

We can do this thanks to previously placed runtime guards that would
redirect all operations to root_task_group's data when RT_GROUP_SCHED
disabled.

Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20250310170442.504716-8-mkoutny@suse.com
pull/1250/head
Michal Koutný 2025-03-10 18:04:39 +01:00 committed by Peter Zijlstra
parent 277e090975
commit d6809c2f60
2 changed files with 33 additions and 12 deletions
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36
kernel/sched/core.c
View File

@ -9867,18 +9867,6 @@ static struct cftype cpu_legacy_files[] = {
.seq_show = cpu_cfs_local_stat_show,
},
#endif
#ifdef CONFIG_RT_GROUP_SCHED
{
.name = "rt_runtime_us",
.read_s64 = cpu_rt_runtime_read,
.write_s64 = cpu_rt_runtime_write,
},
{
.name = "rt_period_us",
.read_u64 = cpu_rt_period_read_uint,
.write_u64 = cpu_rt_period_write_uint,
},
#endif
#ifdef CONFIG_UCLAMP_TASK_GROUP
{
.name = "uclamp.min",
@ -9897,6 +9885,20 @@ static struct cftype cpu_legacy_files[] = {
};
#ifdef CONFIG_RT_GROUP_SCHED
static struct cftype rt_group_files[] = {
{
.name = "rt_runtime_us",
.read_s64 = cpu_rt_runtime_read,
.write_s64 = cpu_rt_runtime_write,
},
{
.name = "rt_period_us",
.read_u64 = cpu_rt_period_read_uint,
.write_u64 = cpu_rt_period_write_uint,
},
{ } /* Terminate */
};
# ifdef CONFIG_RT_GROUP_SCHED_DEFAULT_DISABLED
DEFINE_STATIC_KEY_FALSE(rt_group_sched);
# else
@ -9919,6 +9921,16 @@ static int __init setup_rt_group_sched(char *str)
return 1;
}
__setup("rt_group_sched=", setup_rt_group_sched);
static int __init cpu_rt_group_init(void)
{
if (!rt_group_sched_enabled())
return 0;
WARN_ON(cgroup_add_legacy_cftypes(&cpu_cgrp_subsys, rt_group_files));
return 0;
}
subsys_initcall(cpu_rt_group_init);
#endif /* CONFIG_RT_GROUP_SCHED */
static int cpu_extra_stat_show(struct seq_file *sf,

9
kernel/sched/rt.c
View File

@ -193,6 +193,9 @@ static inline struct rq *rq_of_rt_se(struct sched_rt_entity *rt_se)
void unregister_rt_sched_group(struct task_group *tg)
{
if (!rt_group_sched_enabled())
return;
if (tg->rt_se)
destroy_rt_bandwidth(&tg->rt_bandwidth);
}
@ -201,6 +204,9 @@ void free_rt_sched_group(struct task_group *tg)
{
int i;
if (!rt_group_sched_enabled())
return;
for_each_possible_cpu(i) {
if (tg->rt_rq)
kfree(tg->rt_rq[i]);
@ -245,6 +251,9 @@ int alloc_rt_sched_group(struct task_group *tg, struct task_group *parent)
struct sched_rt_entity *rt_se;
int i;
if (!rt_group_sched_enabled())
return 1;
tg->rt_rq = kcalloc(nr_cpu_ids, sizeof(rt_rq), GFP_KERNEL);
if (!tg->rt_rq)
goto err;