sched/numa: Use unsigned longs for numa group fault stats

As Peter says "If you're going to hold locks you can also do away with all
that atomic_long_*() nonsense". Lock aquisition moved slightly to protect
the updates.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1381141781-10992-63-git-send-email-mgorman@suse.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 20 insertions, 29 deletions

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e7884dc3416d..5b2208e504a4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -916,8 +916,8 @@ struct numa_group {
         struct list_head task_list;
 
         struct rcu_head rcu;
-        atomic_long_t total_faults;
-        atomic_long_t faults[0];
+        unsigned long total_faults;
+        unsigned long faults[0];
 };
 
 pid_t task_numa_group_id(struct task_struct *p)
@@ -944,8 +944,7 @@ static inline unsigned long group_faults(struct task_struct *p, int nid)
         if (!p->numa_group)
                 return 0;
 
-        return atomic_long_read(&p->numa_group->faults[2*nid]) +
-               atomic_long_read(&p->numa_group->faults[2*nid+1]);
+        return p->numa_group->faults[2*nid] + p->numa_group->faults[2*nid+1];
 }
 
 /*
@@ -971,17 +970,10 @@ static inline unsigned long task_weight(struct task_struct *p, int nid)
 
 static inline unsigned long group_weight(struct task_struct *p, int nid)
 {
-        unsigned long total_faults;
-
-        if (!p->numa_group)
-                return 0;
-
-        total_faults = atomic_long_read(&p->numa_group->total_faults);
-
-        if (!total_faults)
+        if (!p->numa_group || !p->numa_group->total_faults)
                 return 0;
 
-        return 1000 * group_faults(p, nid) / total_faults;
+        return 1000 * group_faults(p, nid) / p->numa_group->total_faults;
 }
 
 static unsigned long weighted_cpuload(const int cpu);
@@ -1397,9 +1389,9 @@ static void task_numa_placement(struct task_struct *p)
                         p->total_numa_faults += diff;
                         if (p->numa_group) {
                                 /* safe because we can only change our own group */
-                                atomic_long_add(diff, &p->numa_group->faults[i]);
-                                atomic_long_add(diff, &p->numa_group->total_faults);
-                                group_faults += atomic_long_read(&p->numa_group->faults[i]);
+                                p->numa_group->faults[i] += diff;
+                                p->numa_group->total_faults += diff;
+                                group_faults += p->numa_group->faults[i];
                         }
                 }
 
@@ -1475,7 +1467,7 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
 
         if (unlikely(!p->numa_group)) {
                 unsigned int size = sizeof(struct numa_group) +
-                                    2*nr_node_ids*sizeof(atomic_long_t);
+                                    2*nr_node_ids*sizeof(unsigned long);
 
                 grp = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
                 if (!grp)
@@ -1487,9 +1479,9 @@ static void task_numa_group(struct task_struct *p, int cpupid, int flags,
                 grp->gid = p->pid;
 
                 for (i = 0; i < 2*nr_node_ids; i++)
-                        atomic_long_set(&grp->faults[i], p->numa_faults[i]);
+                        grp->faults[i] = p->numa_faults[i];
 
-                atomic_long_set(&grp->total_faults, p->total_numa_faults);
+                grp->total_faults = p->total_numa_faults;
 
                 list_add(&p->numa_entry, &grp->task_list);
                 grp->nr_tasks++;
@@ -1543,14 +1535,14 @@ unlock:
         if (!join)
                 return;
 
+        double_lock(&my_grp->lock, &grp->lock);
+
         for (i = 0; i < 2*nr_node_ids; i++) {
-                atomic_long_sub(p->numa_faults[i], &my_grp->faults[i]);
-                atomic_long_add(p->numa_faults[i], &grp->faults[i]);
+                my_grp->faults[i] -= p->numa_faults[i];
+                grp->faults[i] += p->numa_faults[i];
         }
-        atomic_long_sub(p->total_numa_faults, &my_grp->total_faults);
-        atomic_long_add(p->total_numa_faults, &grp->total_faults);
-
-        double_lock(&my_grp->lock, &grp->lock);
+        my_grp->total_faults -= p->total_numa_faults;
+        grp->total_faults += p->total_numa_faults;
 
         list_move(&p->numa_entry, &grp->task_list);
         my_grp->nr_tasks--;
@@ -1571,12 +1563,11 @@ void task_numa_free(struct task_struct *p)
         void *numa_faults = p->numa_faults;
 
         if (grp) {
+                spin_lock(&grp->lock);
                 for (i = 0; i < 2*nr_node_ids; i++)
-                        atomic_long_sub(p->numa_faults[i], &grp->faults[i]);
-
-                atomic_long_sub(p->total_numa_faults, &grp->total_faults);
+                        grp->faults[i] -= p->numa_faults[i];
+                grp->total_faults -= p->total_numa_faults;
 
-                spin_lock(&grp->lock);
                 list_del(&p->numa_entry);
                 grp->nr_tasks--;
                 spin_unlock(&grp->lock);