Fair group scheduler - various fixes

here is a few cleanup/simplification/optimization(s) based on the recent modifications in the sched-dev tree.

(3) rework enqueue/dequeue_entity() to get rid of
sched_class::set_curr_task()

Quoted 2 lines

(3) rework enqueue/dequeue_entity() to get rid of
sched_class::set_curr_task()

Dmitry/Ingo,
I am sorry for not having reviewed this change properly, but I
think we need to revert this.

In theory its possible to solve these problems w/o reintroducing set_curr_task(). I tried doing so, but found it clutters dequeue_entity and enqueue_entity a lot and makes it less readable. It will duplicate what put_prev_entity() and set_next_entity() are supposed to do. Moreoever it is slightly inefficient to do all these in dequeue_entity() if we consider that dequeue_entity can be called on current task for other reasons as well (like when it is abt to sleep or change its nice value).

With the view of supporting user-id based fair scheduling (and not just container-based fair scheduling), this patch renames several functions and makes them independent of whether they are being used for container or user-id based fair scheduling.

Also fix a problem reported by KAMEZAWA Hiroyuki (wrt allocating less-sized array for tg->cfs_rq[] and tf->se[]).

Signed-off-by Srivatsa Vaddagiri <[email protected]>

Signed-off-by Dhaval Giani <[email protected]>

---
 include/linux/sched.h |   12 +++
 init/Kconfig          |   11 +--
 kernel/sched.c        |  172 ++++++++++++++++++--------------------------------
 kernel/sched_fair.c   |    5 +
 4 files changed, 83 insertions(+), 117 deletions(-)

Index: current/init/Kconfig
===================================================================

init/Kconfig config CPUSETS · line 285

Quoted 4 lines

config FAIR_GROUP_SCHED

init/Kconfig +1 -2

-	bool "Fair group scheduler"
-	depends on EXPERIMENTAL && CONTAINERS
+	bool "Fair group cpu scheduler"

Can we have "CPU" instead of "cpu" ?

---
 include/linux/sched.h |    4 +++
 init/Kconfig          |   13 ++++++++++++
 kernel/sched.c        |    9 ++++++++
 kernel/sched_debug.c  |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/user.c         |   43 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 121 insertions(+)

Index: linux-2.6.23-rc6/init/Kconfig
===================================================================

init/Kconfig +0 -0

@@ -289,6 +289,19 @@ config FAIR_GROUP_SCHED
 	  This feature lets cpu scheduler recognize task groups and control cpu
 	  bandwidth allocation to such task groups.
 

Quoted 4 lines

init/Kconfig +4 -0

+choice
+	depends on FAIR_GROUP_SCHED
+	prompt "Basis for grouping tasks"
+	default FAIR_USER_SCHED

init/Kconfig config FAIR_GROUP_SCHED · line 301

Quoted 6 lines

init/Kconfig +6 -0

+
+ 	config FAIR_USER_SCHED
+ 		bool "user id"
+ 		help
+ 		  This option will choose userid as the basis for grouping
+		  tasks, thus providing equal cpu bandwidth to each user.

s/cpu/CPU/g please.

and the "bool", "help" and help text are indented by one tab too much.

Enable user-id based fair group scheduling. This is usefull for anyone who wants to test the group scheduler w/o having to enable CONFIG_CGROUPS.

Enable user-id based fair group scheduling. This is usefull for anyone who wants to test the group scheduler w/o having to enable CONFIG_CGROUPS.

A separate scheduling group (i.e struct task_grp) is automatically created for every new user added to the system. Upon uid change for a task, it is made to move to the corresponding scheduling group.

A /proc tunable (/proc/root_user_share) is also provided to tune root user's quota of cpu bandwidth.

Signed-off-by Srivatsa Vaddagiri <[email protected]>

Signed-off-by Dhaval Giani <[email protected]>

---
 include/linux/sched.h |    4 +++
 init/Kconfig          |   13 ++++++++++++
 kernel/sched.c        |    9 ++++++++
 kernel/sched_debug.c  |   52 ++++++++++++++++++++++++++++++++++++++++++++++++++
 kernel/user.c         |   43 +++++++++++++++++++++++++++++++++++++++++
 5 files changed, 121 insertions(+)

Index: linux-2.6.23-rc6/include/linux/sched.h
===================================================================

include/linux/sched.h +4 -0

@@ -596,6 +596,10 @@ struct user_struct {
 	/* Hash table maintenance information */
 	struct hlist_node uidhash_node;
 	uid_t uid;
+
+#ifdef CONFIG_FAIR_USER_SCHED
+	struct task_grp *tg;
+#endif
 };
 
 extern struct user_struct *find_user(uid_t);

Index: linux-2.6.23-rc6/init/Kconfig
===================================================================

init/Kconfig +13 -0

@@ -289,6 +289,19 @@ config FAIR_GROUP_SCHED
 	  This feature lets cpu scheduler recognize task groups and control cpu
 	  bandwidth allocation to such task groups.
 
+choice
+	depends on FAIR_GROUP_SCHED
+	prompt "Basis for grouping tasks"
+	default FAIR_USER_SCHED
+
+ 	config FAIR_USER_SCHED
+ 		bool "user id"
+ 		help
+ 		  This option will choose userid as the basis for grouping
+		  tasks, thus providing equal cpu bandwidth to each user.
+
+endchoice
+
 config SYSFS_DEPRECATED
 	bool "Create deprecated sysfs files"
 	default y

Index: linux-2.6.23-rc6/kernel/sched.c
===================================================================

kernel/sched.c +9 -0

@@ -199,7 +199,12 @@ struct task_grp init_task_grp =  {
 				.cfs_rq = init_cfs_rq_p,
 				 };
 
+#ifdef CONFIG_FAIR_USER_SCHED
+#define INIT_TASK_GRP_LOAD	2*NICE_0_LOAD
+#else
 #define INIT_TASK_GRP_LOAD	NICE_0_LOAD
+#endif
+
 static int init_task_grp_load = INIT_TASK_GRP_LOAD;
 
 /* return group to which a task belongs */

@@ -207,7 +212,11 @@ static inline struct task_grp *task_grp(
 {
 	struct task_grp *tg;
 
+#ifdef CONFIG_FAIR_USER_SCHED
+	tg = p->user->tg;
+#else
 	tg  = &init_task_grp;
+#endif
 
 	return tg;
 }

Index: linux-2.6.23-rc6/kernel/sched_debug.c
===================================================================

kernel/sched_debug.c +4 -0

@@ -214,6 +214,49 @@ static void sysrq_sched_debug_show(void)
 	sched_debug_show(NULL, NULL);
 }
 
+#ifdef CONFIG_FAIR_USER_SCHED
+
+static DEFINE_MUTEX(root_user_share_mutex);
+

kernel/sched_debug.c +38 -0

+
+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_grp_load = shares;
+	rc = sched_group_set_shares(&init_task_grp, 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);

@@ -236,6 +279,15 @@ static int __init init_sched_debug_procf
 
 	pe->proc_fops = &sched_debug_fops;
 
+#ifdef CONFIG_FAIR_USER_SCHED
+	pe = create_proc_entry("root_user_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;
 }
 

Index: linux-2.6.23-rc6/kernel/user.c
===================================================================

kernel/user.c +43 -0

@@ -50,8 +50,41 @@ struct user_struct root_user = {
 	.uid_keyring	= &root_user_keyring,
 	.session_keyring = &root_session_keyring,
 #endif
+#ifdef CONFIG_FAIR_USER_SCHED
+	.tg		= &init_task_grp,
+#endif
 };
 
+#ifdef CONFIG_FAIR_USER_SCHED
+static void sched_destroy_user(struct user_struct *up)
+{
+	sched_destroy_group(up->tg);
+}
+
+static int sched_create_user(struct user_struct *up)
+{
+	int rc = 0;
+
+	up->tg = sched_create_group();
+	if (IS_ERR(up->tg))
+		rc = -ENOMEM;
+
+	return rc;
+}
+
+static void sched_switch_user(struct task_struct *p)
+{
+	sched_move_task(p);
+}
+
+#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) { }
+
+#endif	/* CONFIG_FAIR_USER_SCHED */
+
 /*
  * These routines must be called with the uidhash spinlock held!
  */

@@ -109,6 +142,7 @@ void free_uid(struct user_struct *up)
 	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);

@@ -150,6 +184,13 @@ struct user_struct * alloc_uid(struct us
 			return NULL;
 		}
 
+		if (sched_create_user(new) < 0) {
+			key_put(new->uid_keyring);
+			key_put(new->session_keyring);
+			kmem_cache_free(uid_cachep, new);
+			return NULL;
+		}
+
 		/*
 		 * Before adding this, check whether we raced
 		 * on adding the same user already..

@@ -157,6 +198,7 @@ struct user_struct * alloc_uid(struct us
 		spin_lock_irq(&uidhash_lock);
 		up = uid_hash_find(uid, hashent);
 		if (up) {
+			sched_destroy_user(new);
 			key_put(new->uid_keyring);
 			key_put(new->session_keyring);
 			kmem_cache_free(uid_cachep, new);

@@ -184,6 +226,7 @@ void switch_uid(struct user_struct *new_
 	atomic_dec(&old_user->processes);
 	switch_uid_keyring(new_user);
 	current->user = new_user;
+	sched_switch_user(current);
 
 	/*
 	 * We need to synchronize with __sigqueue_alloc()

kernel/sched_debug.c static void sysrq_sched_debug_show(void) · line 230

Quoted 10 lines

kernel/sched_debug.c +10 -0

+static int
+root_user_share_read_proc(char *page, char **start, off_t off, int count,
+				 int *eof, void *data)
+{
+	int len;
+
+	len = sprintf(page, "%d\n", init_task_grp_load);
+
+	return len;
+}

or use this oneliner:

	return sprintf(page, "%d\n", init_task_grp_load);

 include/linux/cgroup_subsys.h |    6 ++
 init/Kconfig                  |   24 +++++---
 kernel/sched.c                |  122 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 145 insertions(+), 7 deletions(-)

Index: current/init/Kconfig
===================================================================

init/Kconfig +0 -7

@@ -327,13 +327,6 @@ config FAIR_GROUP_SCHED
 	  This feature lets cpu scheduler recognize task groups and control cpu
 	  bandwidth allocation to such task groups.
 
-config RESOURCE_COUNTERS
-	bool "Resource counters"
-	help
-	  This option enables controller independent resource accounting
-          infrastructure that works with cgroups
-	depends on CGROUPS
-
 choice
 	depends on FAIR_GROUP_SCHED
 	prompt "Basis for grouping tasks"

@@ -345,8 +338,25 @@ choice
  		  This option will choose userid as the basis for grouping
 		  tasks, thus providing equal cpu bandwidth to each user.

init/Kconfig choice · line 349

Quoted 9 lines

init/Kconfig +9 -0

+	config FAIR_CGROUP_SCHED
+		bool "Control groups"
+		depends on CGROUPS
+		help
+		   This option allows you to create arbitrary task groups
+		   using the "cgroup" psuedo filesystem and control
+		   the cpu bandwidth allocated to each such task group.
+		   Refer to Documentation/cgroups.txt for more information
+		   on "cgroup" psuedo filesystem.

Too much indentation.

s/cpu/CPU/g please.

init/Kconfig choice · line 357

Quoted 5 lines

init/Kconfig +5 -0

+config RESOURCE_COUNTERS
+	bool "Resource counters"
+	help
+	  This option enables controller independent resource accounting
+          infrastructure that works with cgroups

Use tab + 2 spaces to indent help text.