[RFC/PATCH] Add sysfs control to modify a user's cpu share

Dhaval Giani
2007-10-01T14:09:47Z

Hi Ingo,

Adds tunables in sysfs to modify a user's cpu share.

A directory is created in sysfs for each new user in the system.

/sys/kernel/uids/<uid>/cpu_share

Reading this file returns the cpu shares granted for the user.
Writing into this file modifies the cpu share for the user. Only an
administrator is allowed to modify a user's cpu share.

Ex:
# cd /sys/kernel/uids/
# cat 512/cpu_share
1024
# echo 2048 > 512/cpu_share
# cat 512/cpu_share
2048
#

Signed-off-by: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>

---
include/linux/sched.h | 11 +++++
kernel/ksysfs.c | 4 +
kernel/sched.c | 5 ++
kernel/user.c | 110 +++++++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 129 insertions(+), 1 deletion(-)

Index: linux-2.6.23-rc8-sched-devel/include/linux/sched.h
===================================================================
--- linux-2.6.23-rc8-sched-devel.orig/include/linux/sched.h
+++ linux-2.6.23-rc8-sched-devel/include/linux/sched.h
@@ -86,6 +86,7 @@ struct sched_param {
#include <linux/timer.h>
#include <linux/hrtimer.h>
#include <linux/task_io_accounting.h>
+#include <linux/kobject.h>

#include <asm/processor.h>

@@ -598,9 +599,18 @@ struct user_struct {

#ifdef CONFIG_FAIR_USER_SCHED
struct task_group *tg;
+ struct kset kset;
+ struct subsys_attribute user_attr;
+ struct work_struct work;
#endif
};

+#ifdef CONFIG_FAIR_USER_SCHED
+extern int uids_kobject_init(void);
+#else
+static inline int uids_kobject_init(void) { return 0; }
+#endif
+
extern struct user_struct *find_user(uid_t);

extern struct user_struct root_user;
@@ -1846,6 +1856,7 @@ extern struct task_group *sched_create_g
extern void sched_destroy_group(struct task_group *tg);
extern void sched_move_task(struct task_struct *tsk);
extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);
+extern unsigned long sched_group_shares(struct task_group *tg);

#endif

Index: linux-2.6.23-rc8-sched-devel/kernel/ksysfs.c
===================================================================
--- linux-2.6.23-rc8-sched-devel.orig/kernel/ksysfs.c
+++ linux-2.6.23-rc8-sched-devel/kernel/ksysfs.c
@@ -14,6 +14,7 @@
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kexec.h>
+#include <linux/sched.h>

#define KERNEL_ATTR_RO(_name) \
static struct subsys_attribute _name##_attr = __ATTR_RO(_name)
@@ -116,6 +117,9 @@ static int __init ksysfs_init(void)
&notes_attr);
}

+ if (!error)
+ error = uids_kobject_init();
+
return error;
}

Index: linux-2.6.23-rc8-sched-devel/kernel/sched.c
===================================================================
--- linux-2.6.23-rc8-sched-devel.orig/kernel/sched.c
+++ linux-2.6.23-rc8-sched-devel/kernel/sched.c
@@ -6928,4 +6928,9 @@ int sched_group_set_shares(struct task_g
return 0;
}

+unsigned long sched_group_shares(struct task_group *tg)
+{
+ return tg->shares;
+}
+
#endif /* CONFIG_FAIR_GROUP_SCHED */
Index: linux-2.6.23-rc8-sched-devel/kernel/user.c
===================================================================
--- linux-2.6.23-rc8-sched-devel.orig/kernel/user.c
+++ linux-2.6.23-rc8-sched-devel/kernel/user.c
@@ -56,6 +56,62 @@ struct user_struct root_user = {
};

#ifdef CONFIG_FAIR_USER_SCHED
+
+static struct kobject uids_kobject;
+
+ssize_t cpu_shares_show(struct kset *kset, char *buffer)
+{
+ struct user_struct *up = container_of(kset, struct user_struct, kset);
+
+ return sprintf(buffer, "%lu\n", sched_group_shares(up->tg));
+}
+
+ssize_t cpu_shares_store(struct kset *kset, const char *buffer, size_t size)
+{
+ struct user_struct *up = container_of(kset, struct user_struct, kset);
+ unsigned long shares;
+ int rc;
+
+ sscanf(buffer, "%lu", &shares);
+
+ rc = sched_group_set_shares(up->tg, shares);
+
+ return (rc ? rc : size);
+}
+
+static void user_attr_init(struct subsys_attribute *sa, char *name, int mode)
+{
+ sa->attr.name = name;
+ sa->attr.mode = mode;
+ sa->show = cpu_shares_show;
+ sa->store = cpu_shares_store;
+}
+
+static int user_kobject_create(struct user_struct *up)
+{
+ struct kset *kset = &up->kset;
+ struct kobject *kobj = &kset->kobj;
+ int error;
+
+ memset(kset, 0, sizeof(struct kset));
+ kobj->parent = &uids_kobject;
+ kobject_set_name(kobj, "%d", up->uid);
+ kset_init(kset);
+ user_attr_init(&up->user_attr, "cpu_share", 0644);
+
+ error = kobject_add(kobj);
+
+ if (error)
+ goto done;
+
+ error = sysfs_create_file(kobj, &up->user_attr.attr);
+ if (error)
+ kobject_del(kobj);
+
+done:
+ return error;
+}
+
static void sched_destroy_user(struct user_struct *up)
{
sched_destroy_group(up->tg);
@@ -77,11 +133,53 @@ static void sched_switch_user(struct tas
sched_move_task(p);
}

+int __init uids_kobject_init(void)
+{
+ int error;
+
+ uids_kobject.parent = &kernel_subsys.kobj;
+ kobject_set_name(&uids_kobject, "uids");
+ kobject_init(&uids_kobject);
+ error = kobject_add(&uids_kobject);
+
+ if (!error)
+ error = user_kobject_create(&root_user);
+
+ return error;
+}
+
+static void remove_user_sysfs_dir(struct work_struct *w)
+{
+ struct user_struct *up = container_of(w, struct user_struct, work);
+ struct kobject *kobj = &up->kset.kobj;
+
+ sysfs_remove_file(kobj, &up->user_attr.attr);
+ kobject_del(kobj);
+ kmem_cache_free(uid_cachep, up);
+}
+
+static inline void free_user(struct user_struct *up)
+{
+ struct kobject *kobj = &up->kset.kobj;
+
+ if (!kobj->sd)
+ return;
+
+ INIT_WORK(&up->work, remove_user_sysfs_dir);
+ schedule_work(&up->work);
+}
+
#else /* CONFIG_FAIR_USER_SCHED */

static void sched_destroy_user(struct user_struct *up) { }
static int sched_create_user(struct user_struct *up) { return 0; }
static void sched_switch_user(struct task_struct *p) { }
+static inline int user_kobject_create(struct user_struct *up) { return 0; }
+
+static inline void free_user(struct user_struct *up)
+{
+ kmem_cache_free(uid_cachep, up);
+}

#endif /* CONFIG_FAIR_USER_SCHED */

@@ -145,7 +243,7 @@ void free_uid(struct user_struct *up)
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
- kmem_cache_free(uid_cachep, up);
+ free_user(up);
} else {
local_irq_restore(flags);
}
@@ -155,6 +253,7 @@ struct user_struct * alloc_uid(struct us
{
struct hlist_head *hashent = uidhashentry(ns, uid);
struct user_struct *up;
+ int create_sysfs_dir = 0;

spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
@@ -205,10 +304,19 @@ struct user_struct * alloc_uid(struct us
} else {
uid_hash_insert(new, hashent);
up = new;
+ create_sysfs_dir = 1;
}
spin_unlock_irq(&uidhash_lock);

}
+
+ if (create_sysfs_dir) {
+ if (user_kobject_create(up)) {
+ free_uid(up);
+ up = NULL;
+ }
+ }
+
return up;
}

--
regards,
Dhaval