numa: add a sysctl for numa_balancing

Add a working sysctl to enable/disable automatic numa memory balancing
at runtime.

This allows us to track down performance problems with this feature and
is generally a good idea.

This was possible earlier through debugfs, but only with special
debugging options set.  Also fix the boot message.

[akpm@linux-foundation.org: s/sched_numa_balancing/sysctl_numa_balancing/]
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

4 files changed, 37 insertions, 2 deletions

diff --git a/include/linux/sched/sysctl.h b/include/linux/sched/sysctl.h
index 31e0193cb0c5..b13cf430764f 100644
--- a/include/linux/sched/sysctl.h
+++ b/include/linux/sched/sysctl.h
@@ -99,4 +99,8 @@ extern int sched_rt_handler(struct ctl_table *table, int write,
                 void __user *buffer, size_t *lenp,
                 loff_t *ppos);
 
+extern int sysctl_numa_balancing(struct ctl_table *table, int write,
+                                 void __user *buffer, size_t *lenp,
+                                 loff_t *ppos);
+
 #endif /* _SCHED_SYSCTL_H */
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4d6964e49711..7fea865a810d 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1770,7 +1770,29 @@ void set_numabalancing_state(bool enabled)
         numabalancing_enabled = enabled;
 }
 #endif /* CONFIG_SCHED_DEBUG */
-#endif /* CONFIG_NUMA_BALANCING */
+
+#ifdef CONFIG_PROC_SYSCTL
+int sysctl_numa_balancing(struct ctl_table *table, int write,
+                         void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+        struct ctl_table t;
+        int err;
+        int state = numabalancing_enabled;
+
+        if (write && !capable(CAP_SYS_ADMIN))
+                return -EPERM;
+
+        t = *table;
+        t.data = &state;
+        err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos);
+        if (err < 0)
+                return err;
+        if (write)
+                set_numabalancing_state(state);
+        return err;
+}
+#endif
+#endif
 
 /*
  * fork()/clone()-time setup:
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 332cefcdb04b..693eac39c202 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -389,6 +389,15 @@ static struct ctl_table kern_table[] = {
                 .mode           = 0644,
                 .proc_handler   = proc_dointvec,
         },
+        {
+                .procname       = "numa_balancing",
+                .data           = NULL, /* filled in by handler */
+                .maxlen         = sizeof(unsigned int),
+                .mode           = 0644,
+                .proc_handler   = sysctl_numa_balancing,
+                .extra1         = &zero,
+                .extra2         = &one,
+        },
 #endif /* CONFIG_NUMA_BALANCING */
 #endif /* CONFIG_SCHED_DEBUG */
         {
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 0cd2c4d4e270..947293e76533 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -2668,7 +2668,7 @@ static void __init check_numabalancing_enable(void)
 
         if (nr_node_ids > 1 && !numabalancing_override) {
                 printk(KERN_INFO "Enabling automatic NUMA balancing. "
-                        "Configure with numa_balancing= or sysctl");
+                        "Configure with numa_balancing= or the kernel.numa_balancing sysctl");
                 set_numabalancing_state(numabalancing_default);
         }
 }