sched: add fair-user scheduler

Enable user-id based fair group scheduling. This is useful 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 <vatsa@linux.vnet.ibm.com>
Signed-off-by: Dhaval Giani <dhaval@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 52 insertions, 0 deletions

diff --git a/kernel/sched_debug.c b/kernel/sched_debug.c
index 3e47e870b043..57ee9d5630a8 100644
--- a/kernel/sched_debug.c
+++ b/kernel/sched_debug.c
@@ -212,6 +212,49 @@ static void sysrq_sched_debug_show(void)
         sched_debug_show(NULL, NULL);
 }
 
+#ifdef CONFIG_FAIR_USER_SCHED
+
+static DEFINE_MUTEX(root_user_share_mutex);
+
+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;
+}
+
+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);
@@ -234,6 +277,15 @@ 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_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;
 }