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sched/topology: Allocate per-CPU sched_domain_shared in s_data

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The "sched_domain_shared" object is allocated for every topology level
in __sdt_alloc() and is freed post sched domain rebuild if they aren't
assigned during sd_init().

"sd->shared" is only assigned for SD_SHARE_LLC domains and out of all
the assigned objects, only "sd_llc_shared" is ever used by the
scheduler.

Since only "sd_llc_shared" is ever used, and since SD_SHARE_LLC domains
never overlap, allocate only a single range of per-CPU
"sched_domain_shared" object with s_data instead of doing it per
topology level.

The subsequent commit uses the degeneration path to correctly assign the
"sd->shared" to the topmost SD_SHARE_LLC domain.

No functional changes are expected at this point.

Signed-off-by: K Prateek Nayak <kprateek.nayak@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Reviewed-by: Chen Yu <yu.c.chen@intel.com>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Link: https://patch.msgid.link/20260312044434.1974-4-kprateek.nayak@amd.com
This commit is contained in:
K Prateek Nayak 2026-03-12 04:44:28 +00:00 committed by Peter Zijlstra
parent 5a7b576b3e
commit 1cc8a33ca7
1 changed files with 47 additions and 1 deletions
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48
kernel/sched/topology.c
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@ -782,6 +782,7 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu)
}
struct s_data {
struct sched_domain_shared * __percpu *sds;
struct sched_domain * __percpu *sd;
struct root_domain *rd;
};
@ -789,6 +790,7 @@ struct s_data {
enum s_alloc {
sa_rootdomain,
sa_sd,
sa_sd_shared,
sa_sd_storage,
sa_none,
};
@ -1535,6 +1537,9 @@ static void set_domain_attribute(struct sched_domain *sd,
static void __sdt_free(const struct cpumask *cpu_map);
static int __sdt_alloc(const struct cpumask *cpu_map);
static void __sds_free(struct s_data *d, const struct cpumask *cpu_map);
static int __sds_alloc(struct s_data *d, const struct cpumask *cpu_map);
static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
const struct cpumask *cpu_map)
{
@ -1546,6 +1551,9 @@ static void __free_domain_allocs(struct s_data *d, enum s_alloc what,
case sa_sd:
free_percpu(d->sd);
fallthrough;
case sa_sd_shared:
__sds_free(d, cpu_map);
fallthrough;
case sa_sd_storage:
__sdt_free(cpu_map);
fallthrough;
@ -1561,9 +1569,11 @@ __visit_domain_allocation_hell(struct s_data *d, const struct cpumask *cpu_map)
if (__sdt_alloc(cpu_map))
return sa_sd_storage;
if (__sds_alloc(d, cpu_map))
return sa_sd_shared;
d->sd = alloc_percpu(struct sched_domain *);
if (!d->sd)
return sa_sd_storage;
return sa_sd_shared;
d->rd = alloc_rootdomain();
if (!d->rd)
return sa_sd;
@ -2464,6 +2474,42 @@ static void __sdt_free(const struct cpumask *cpu_map)
}
}
static int __sds_alloc(struct s_data *d, const struct cpumask *cpu_map)
{
int j;
d->sds = alloc_percpu(struct sched_domain_shared *);
if (!d->sds)
return -ENOMEM;
for_each_cpu(j, cpu_map) {
struct sched_domain_shared *sds;
sds = kzalloc_node(sizeof(struct sched_domain_shared),
GFP_KERNEL, cpu_to_node(j));
if (!sds)
return -ENOMEM;
*per_cpu_ptr(d->sds, j) = sds;
}
return 0;
}
static void __sds_free(struct s_data *d, const struct cpumask *cpu_map)
{
int j;
if (!d->sds)
return;
for_each_cpu(j, cpu_map)
kfree(*per_cpu_ptr(d->sds, j));
free_percpu(d->sds);
d->sds = NULL;
}
static struct sched_domain *build_sched_domain(struct sched_domain_topology_level *tl,
const struct cpumask *cpu_map, struct sched_domain_attr *attr,
struct sched_domain *child, int cpu)