[PATCH 13/15] sched/isolation: Implement sysfs interface for dynamic housekeeping

Qiliang Yuan
2026-03-25T09:11:27Z

Subsystem housekeeping masks are currently static and can only be set
via boot-time parameters (isolcpus, nohz_full, etc.). There is no
userspace interface to reconfigure these boundaries at runtime.

Implement the DHEI sysfs interface under /sys/kernel/housekeeping.

This enables userspace to independently reconfigure different kernel
services' affinities without a reboot.

Signed-off-by: Qiliang Yuan <realwujing@gmail.com>
---
kernel/sched/isolation.c | 89 ++++++++++++++++++++++++------------------------
1 file changed, 45 insertions(+), 44 deletions(-)

diff --git a/kernel/sched/isolation.c b/kernel/sched/isolation.c
index 685cc0df1bd9f..1c867784d155b 100644
--- a/kernel/sched/isolation.c
+++ b/kernel/sched/isolation.c
@@ -8,7 +8,12 @@
*
*/
#include <linux/sched/isolation.h>
+#include <linux/capability.h>
#include <linux/mutex.h>
+#include <linux/kobject.h>
+#include <linux/sysfs.h>
+#include <linux/slab.h>
+#include <linux/ctype.h>
#include <linux/notifier.h>
#include <linux/topology.h>
#include "sched.h"
@@ -16,9 +21,17 @@
enum hk_flags {
HK_FLAG_DOMAIN = BIT(HK_TYPE_DOMAIN),
HK_FLAG_MANAGED_IRQ = BIT(HK_TYPE_MANAGED_IRQ),
- HK_FLAG_KERNEL_NOISE = BIT(HK_TYPE_KERNEL_NOISE),
+ HK_FLAG_TICK = BIT(HK_TYPE_TICK),
+ HK_FLAG_TIMER = BIT(HK_TYPE_TIMER),
+ HK_FLAG_RCU = BIT(HK_TYPE_RCU),
+ HK_FLAG_MISC = BIT(HK_TYPE_MISC),
+ HK_FLAG_WQ = BIT(HK_TYPE_WQ),
+ HK_FLAG_KTHREAD = BIT(HK_TYPE_KTHREAD),
};

+#define HK_FLAG_KERNEL_NOISE (HK_FLAG_TICK | HK_FLAG_TIMER | HK_FLAG_RCU | \
+ HK_FLAG_MISC | HK_FLAG_WQ | HK_FLAG_KTHREAD)
+
static DEFINE_MUTEX(housekeeping_mutex);
static BLOCKING_NOTIFIER_HEAD(housekeeping_notifier_list);
DEFINE_STATIC_KEY_FALSE(housekeeping_overridden);
@@ -44,6 +57,9 @@ static ssize_t smt_aware_store(struct kobject *kobj,
{
bool val;

+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
if (kstrtobool(buf, &val))
return -EINVAL;

@@ -53,7 +69,7 @@ static ssize_t smt_aware_store(struct kobject *kobj,
}

static struct kobj_attribute smt_aware_attr =
- __ATTR(smt_aware_mode, 0644, smt_aware_show, smt_aware_store);
+ __ATTR(smt_aware_mode, 0600, smt_aware_show, smt_aware_store);

bool housekeeping_enabled(enum hk_type type)
{
@@ -171,6 +187,9 @@ static ssize_t housekeeping_store(struct kobject *kobject,
cpumask_var_t new_mask;
int err;

+ if (!capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
if (!alloc_cpumask_var(&new_mask, GFP_KERNEL))
return -ENOMEM;

@@ -178,42 +197,26 @@ static ssize_t housekeeping_store(struct kobject *kobject,
if (err)
goto out_free;

- /* Safety check: must have at least one online CPU for housekeeping */
- if (!cpumask_intersects(new_mask, cpu_online_mask)) {
+ if (cpumask_empty(new_mask) ||
+ !cpumask_intersects(new_mask, cpu_online_mask)) {
err = -EINVAL;
goto out_free;
}

- if (housekeeping_smt_aware) {
- int cpu, sibling;
- cpumask_var_t tmp_mask;
+ mutex_lock(&housekeeping_mutex);

- if (!alloc_cpumask_var(&tmp_mask, GFP_KERNEL)) {
- err = -ENOMEM;
- goto out_free;
- }
+ if (housekeeping_smt_aware) {
+ int cpu;

- cpumask_copy(tmp_mask, new_mask);
- for_each_cpu(cpu, tmp_mask) {
- for_each_cpu(sibling, topology_sibling_cpumask(cpu)) {
- if (!cpumask_test_cpu(sibling, tmp_mask)) {
- /* SMT sibling should stay grouped */
- cpumask_clear_cpu(cpu, new_mask);
- break;
- }
+ for_each_cpu(cpu, new_mask) {
+ if (!cpumask_subset(topology_sibling_cpumask(cpu),
+ new_mask)) {
+ err = -EINVAL;
+ goto out_unlock;
}
}
- free_cpumask_var(tmp_mask);
-
- /* Re-check after SMT sync */
- if (!cpumask_intersects(new_mask, cpu_online_mask)) {
- err = -EINVAL;
- goto out_free;
- }
}

- mutex_lock(&housekeeping_mutex);
-
if (!housekeeping.cpumasks[type]) {
if (!alloc_cpumask_var(&housekeeping.cpumasks[type], GFP_KERNEL)) {
err = -ENOMEM;
@@ -242,7 +245,7 @@ static ssize_t housekeeping_store(struct kobject *kobject,
}

static struct hk_attribute housekeeping_attrs[HK_TYPE_MAX];
-static struct attribute *housekeeping_attr_ptr[HK_TYPE_MAX + 1];
+static struct attribute *housekeeping_attr_ptr[HK_TYPE_MAX + 2];

static const struct attribute_group housekeeping_attr_group = {
.attrs = housekeeping_attr_ptr,
@@ -265,28 +268,22 @@ static int __init housekeeping_sysfs_init(void)
housekeeping_attrs[i].type = i;
sysfs_attr_init(&housekeeping_attrs[i].kattr.attr);
housekeeping_attrs[i].kattr.attr.name = hk_type_names[i];
- housekeeping_attrs[i].kattr.attr.mode = 0644;
+ housekeeping_attrs[i].kattr.attr.mode = 0600;
housekeeping_attrs[i].kattr.show = housekeeping_show;
housekeeping_attrs[i].kattr.store = housekeeping_store;
housekeeping_attr_ptr[j++] = &housekeeping_attrs[i].kattr.attr;
}
+
+ housekeeping_attr_ptr[j++] = &smt_aware_attr.attr;
housekeeping_attr_ptr[j] = NULL;

ret = sysfs_create_group(housekeeping_kobj, &housekeeping_attr_group);
- if (ret)
- goto err_group;
-
- ret = sysfs_create_file(housekeeping_kobj, &smt_aware_attr.attr);
- if (ret)
- goto err_file;
+ if (ret) {
+ kobject_put(housekeeping_kobj);
+ return ret;
+ }

return 0;
-
-err_file:
- sysfs_remove_group(housekeeping_kobj, &housekeeping_attr_group);
-err_group:
- kobject_put(housekeeping_kobj);
- return ret;
}
late_initcall(housekeeping_sysfs_init);

@@ -313,8 +310,12 @@ static void __init housekeeping_setup_type(enum hk_type type,
if (!slab_is_available())
gfp = GFP_NOWAIT;

- if (!housekeeping.cpumasks[type])
- alloc_cpumask_var(&housekeeping.cpumasks[type], gfp);
+ if (!housekeeping.cpumasks[type]) {
+ if (!alloc_cpumask_var(&housekeeping.cpumasks[type], gfp)) {
+ pr_err("housekeeping: failed to allocate cpumask for type %d\n", type);
+ return;
+ }
+ }

cpumask_copy(housekeeping.cpumasks[type],
housekeeping_staging);

--
2.43.0