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sched: group scheduling, sysfs tunables 

Add 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>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Dhaval Giani 2007-10-15 17:00:14 +02:00 committed by Ingo Molnar
parent 8ca0e14ffb
commit 5cb350baf5
6 changed files with 317 additions and 87 deletions
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67
Documentation/sched-design-CFS.txt
View File

@ -117,3 +117,70 @@ Some implementation details:
iterators of the scheduling modules are used. The balancing code got
quite a bit simpler as a result.
Group scheduler extension to CFS
================================
Normally the scheduler operates on individual tasks and strives to provide
fair CPU time to each task. Sometimes, it may be desirable to group tasks
and provide fair CPU time to each such task group. For example, it may
be desirable to first provide fair CPU time to each user on the system
and then to each task belonging to a user.
CONFIG_FAIR_GROUP_SCHED strives to achieve exactly that. It lets
SCHED_NORMAL/BATCH tasks be be grouped and divides CPU time fairly among such
groups. At present, there are two (mutually exclusive) mechanisms to group
tasks for CPU bandwidth control purpose:
- Based on user id (CONFIG_FAIR_USER_SCHED)
In this option, tasks are grouped according to their user id.
- Based on "cgroup" pseudo filesystem (CONFIG_FAIR_CGROUP_SCHED)
This options lets the administrator create arbitrary groups
of tasks, using the "cgroup" pseudo filesystem. See
Documentation/cgroups.txt for more information about this
filesystem.
Only one of these options to group tasks can be chosen and not both.
Group scheduler tunables:
When CONFIG_FAIR_USER_SCHED is defined, a directory is created in sysfs for
each new user and a "cpu_share" file is added in that directory.
# cd /sys/kernel/uids
# cat 512/cpu_share # Display user 512's CPU share
1024
# echo 2048 > 512/cpu_share # Modify user 512's CPU share
# cat 512/cpu_share # Display user 512's CPU share
2048
#
CPU bandwidth between two users are divided in the ratio of their CPU shares.
For ex: if you would like user "root" to get twice the bandwidth of user
"guest", then set the cpu_share for both the users such that "root"'s
cpu_share is twice "guest"'s cpu_share
When CONFIG_FAIR_CGROUP_SCHED is defined, a "cpu.shares" file is created
for each group created using the pseudo filesystem. See example steps
below to create task groups and modify their CPU share using the "cgroups"
pseudo filesystem
# mkdir /dev/cpuctl
# mount -t cgroup -ocpu none /dev/cpuctl
# cd /dev/cpuctl
# mkdir multimedia # create "multimedia" group of tasks
# mkdir browser # create "browser" group of tasks
# #Configure the multimedia group to receive twice the CPU bandwidth
# #that of browser group
# echo 2048 > multimedia/cpu.shares
# echo 1024 > browser/cpu.shares
# firefox & # Launch firefox and move it to "browser" group
# echo <firefox_pid> > browser/tasks
# #Launch gmplayer (or your favourite movie player)
# echo <movie_player_pid> > multimedia/tasks

11
include/linux/sched.h
View File

@ -87,6 +87,7 @@ 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>
@ -599,9 +600,18 @@ 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;
@ -1848,6 +1858,7 @@ extern struct task_group *sched_create_group(void);
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

8
kernel/ksysfs.c
View File

@ -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 +117,13 @@ static int __init ksysfs_init(void)
&notes_attr);
}
/*
* Create "/sys/kernel/uids" directory and corresponding root user's
* directory under it.
*/
if (!error)
error = uids_kobject_init();
return error;
}

14
kernel/sched.c
View File

@ -162,6 +162,8 @@ struct task_group {
/* runqueue "owned" by this group on each cpu */
struct cfs_rq **cfs_rq;
unsigned long shares;
/* spinlock to serialize modification to shares */
spinlock_t lock;
};
/* Default task group's sched entity on each cpu */
@ -6533,6 +6535,7 @@ void __init sched_init(void)
se->parent = NULL;
}
init_task_group.shares = init_task_group_load;
spin_lock_init(&init_task_group.lock);
#endif
for (j = 0; j < CPU_LOAD_IDX_MAX; j++)
@ -6777,6 +6780,7 @@ struct task_group *sched_create_group(void)
}
tg->shares = NICE_0_LOAD;
spin_lock_init(&tg->lock);
return tg;
@ -6897,8 +6901,9 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
{
int i;
spin_lock(&tg->lock);
if (tg->shares == shares)
return 0;
goto done;
/* return -EINVAL if the new value is not sane */
@ -6906,7 +6911,14 @@ int sched_group_set_shares(struct task_group *tg, unsigned long shares)
for_each_possible_cpu(i)
set_se_shares(tg->se[i], shares);
done:
spin_unlock(&tg->lock);
return 0;
}
unsigned long sched_group_shares(struct task_group *tg)
{
return tg->shares;
}
#endif /* CONFIG_FAIR_GROUP_SCHED */

48
kernel/sched_debug.c
View File

@ -231,45 +231,6 @@ static void sysrq_sched_debug_show(void)
sched_debug_show(NULL, NULL);
}
#ifdef CONFIG_FAIR_USER_SCHED
static DEFINE_MUTEX(root_user_share_mutex);
static int
root_user_share_read_proc(char *page, char **start, off_t off, int count,
int *eof, void *data)
{
return sprintf(page, "%d\n", init_task_group_load);
}
static int
root_user_share_write_proc(struct file *file, const char __user *buffer,
unsigned long count, void *data)
{
unsigned long shares;
char kbuf[sizeof(unsigned long)+1];
int rc = 0;
if (copy_from_user(kbuf, buffer, sizeof(kbuf)))
return -EFAULT;
shares = simple_strtoul(kbuf, NULL, 0);
if (!shares)
shares = NICE_0_LOAD;
mutex_lock(&root_user_share_mutex);
init_task_group_load = shares;
rc = sched_group_set_shares(&init_task_group, shares);
mutex_unlock(&root_user_share_mutex);
return (rc < 0 ? rc : count);
}
#endif /* CONFIG_FAIR_USER_SCHED */
static int sched_debug_open(struct inode *inode, struct file *filp)
{
return single_open(filp, sched_debug_show, NULL);
@ -292,15 +253,6 @@ static int __init init_sched_debug_procfs(void)
pe->proc_fops = &sched_debug_fops;
#ifdef CONFIG_FAIR_USER_SCHED
pe = create_proc_entry("root_user_cpu_share", 0644, NULL);
if (!pe)
return -ENOMEM;
pe->read_proc = root_user_share_read_proc;
pe->write_proc = root_user_share_write_proc;
#endif
return 0;
}

256
kernel/user.c
View File

@ -55,7 +55,41 @@ struct user_struct root_user = {
#endif
};
/*
* These routines must be called with the uidhash spinlock held!
*/
static inline void uid_hash_insert(struct user_struct *up,
struct hlist_head *hashent)
{
hlist_add_head(&up->uidhash_node, hashent);
}
static inline void uid_hash_remove(struct user_struct *up)
{
hlist_del_init(&up->uidhash_node);
}
static inline struct user_struct *uid_hash_find(uid_t uid,
struct hlist_head *hashent)
{
struct user_struct *user;
struct hlist_node *h;
hlist_for_each_entry(user, h, hashent, uidhash_node) {
if (user->uid == uid) {
atomic_inc(&user->__count);
return user;
}
}
return NULL;
}
#ifdef CONFIG_FAIR_USER_SCHED
static struct kobject uids_kobject; /* represents /sys/kernel/uids directory */
static DEFINE_MUTEX(uids_mutex);
static void sched_destroy_user(struct user_struct *up)
{
sched_destroy_group(up->tg);
@ -77,42 +111,173 @@ static void sched_switch_user(struct task_struct *p)
sched_move_task(p);
}
static inline void uids_mutex_lock(void)
{
mutex_lock(&uids_mutex);
}
static inline void uids_mutex_unlock(void)
{
mutex_unlock(&uids_mutex);
}
/* return cpu shares held by the user */
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));
}
/* modify cpu shares held by the user */
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;
}
/* Create "/sys/kernel/uids/<uid>" directory and
* "/sys/kernel/uids/<uid>/cpu_share" file for this user.
*/
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; /* create under /sys/kernel/uids dir */
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;
}
/* create these in sysfs filesystem:
* "/sys/kernel/uids" directory
* "/sys/kernel/uids/0" directory (for root user)
* "/sys/kernel/uids/0/cpu_share" file (for root user)
*/
int __init uids_kobject_init(void)
{
int error;
/* create under /sys/kernel dir */
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;
}
/* work function to remove sysfs directory for a user and free up
* corresponding structures.
*/
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;
unsigned long flags;
int remove_user = 0;
/* Make uid_hash_remove() + sysfs_remove_file() + kobject_del()
* atomic.
*/
uids_mutex_lock();
local_irq_save(flags);
if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
uid_hash_remove(up);
remove_user = 1;
spin_unlock_irqrestore(&uidhash_lock, flags);
} else {
local_irq_restore(flags);
}
if (!remove_user)
goto done;
sysfs_remove_file(kobj, &up->user_attr.attr);
kobject_del(kobj);
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
done:
uids_mutex_unlock();
}
/* IRQs are disabled and uidhash_lock is held upon function entry.
* IRQ state (as stored in flags) is restored and uidhash_lock released
* upon function exit.
*/
static inline void free_user(struct user_struct *up, unsigned long flags)
{
/* restore back the count */
atomic_inc(&up->__count);
spin_unlock_irqrestore(&uidhash_lock, flags);
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 uids_mutex_lock(void) { }
static inline void uids_mutex_unlock(void) { }
/* IRQs are disabled and uidhash_lock is held upon function entry.
* IRQ state (as stored in flags) is restored and uidhash_lock released
* upon function exit.
*/
static inline void free_user(struct user_struct *up, unsigned long flags)
{
uid_hash_remove(up);
spin_unlock_irqrestore(&uidhash_lock, flags);
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
}
#endif /* CONFIG_FAIR_USER_SCHED */
/*
* These routines must be called with the uidhash spinlock held!
*/
static inline void uid_hash_insert(struct user_struct *up, struct hlist_head *hashent)
{
hlist_add_head(&up->uidhash_node, hashent);
}
static inline void uid_hash_remove(struct user_struct *up)
{
hlist_del_init(&up->uidhash_node);
}
static inline struct user_struct *uid_hash_find(uid_t uid, struct hlist_head *hashent)
{
struct user_struct *user;
struct hlist_node *h;
hlist_for_each_entry(user, h, hashent, uidhash_node) {
if(user->uid == uid) {
atomic_inc(&user->__count);
return user;
}
}
return NULL;
}
/*
* Locate the user_struct for the passed UID. If found, take a ref on it. The
* caller must undo that ref with free_uid().
@ -139,16 +304,10 @@ void free_uid(struct user_struct *up)
return;
local_irq_save(flags);
if (atomic_dec_and_lock(&up->__count, &uidhash_lock)) {
uid_hash_remove(up);
spin_unlock_irqrestore(&uidhash_lock, flags);
sched_destroy_user(up);
key_put(up->uid_keyring);
key_put(up->session_keyring);
kmem_cache_free(uid_cachep, up);
} else {
if (atomic_dec_and_lock(&up->__count, &uidhash_lock))
free_user(up, flags);
else
local_irq_restore(flags);
}
}
struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
@ -156,6 +315,11 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
struct hlist_head *hashent = uidhashentry(ns, uid);
struct user_struct *up;
/* Make uid_hash_find() + user_kobject_create() + uid_hash_insert()
* atomic.
*/
uids_mutex_lock();
spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
spin_unlock_irq(&uidhash_lock);
@ -191,6 +355,15 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
return NULL;
}
if (user_kobject_create(new)) {
sched_destroy_user(new);
key_put(new->uid_keyring);
key_put(new->session_keyring);
kmem_cache_free(uid_cachep, new);
uids_mutex_unlock();
return NULL;
}
/*
* Before adding this, check whether we raced
* on adding the same user already..
@ -198,7 +371,11 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
spin_lock_irq(&uidhash_lock);
up = uid_hash_find(uid, hashent);
if (up) {
sched_destroy_user(new);
/* This case is not possible when CONFIG_FAIR_USER_SCHED
* is defined, since we serialize alloc_uid() using
* uids_mutex. Hence no need to call
* sched_destroy_user() or remove_user_sysfs_dir().
*/
key_put(new->uid_keyring);
key_put(new->session_keyring);
kmem_cache_free(uid_cachep, new);
@ -209,6 +386,9 @@ struct user_struct * alloc_uid(struct user_namespace *ns, uid_t uid)
spin_unlock_irq(&uidhash_lock);
}
uids_mutex_unlock();
return up;
}