[PATCH] sched: schedstats update for balance on fork

Add SCHEDSTAT statistics for sched-balance-fork.

Signed-off-by: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 44 insertions, 29 deletions

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 613491d3a875..36a10781c3f3 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -517,10 +517,16 @@ struct sched_domain {
         unsigned long alb_failed;
         unsigned long alb_pushed;
 
-        /* sched_balance_exec() stats */
-        unsigned long sbe_attempts;
+        /* SD_BALANCE_EXEC stats */
+        unsigned long sbe_cnt;
+        unsigned long sbe_balanced;
         unsigned long sbe_pushed;
 
+        /* SD_BALANCE_FORK stats */
+        unsigned long sbf_cnt;
+        unsigned long sbf_balanced;
+        unsigned long sbf_pushed;
+
         /* try_to_wake_up() stats */
         unsigned long ttwu_wake_remote;
         unsigned long ttwu_move_affine;
diff --git a/kernel/sched.c b/kernel/sched.c
index 7ecc237e2aab..2711130cd973 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -309,7 +309,7 @@ static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
  * bump this up when changing the output format or the meaning of an existing
  * format, so that tools can adapt (or abort)
  */
-#define SCHEDSTAT_VERSION 11
+#define SCHEDSTAT_VERSION 12
 
 static int show_schedstat(struct seq_file *seq, void *v)
 {
@@ -356,9 +356,10 @@ static int show_schedstat(struct seq_file *seq, void *v)
                                     sd->lb_nobusyq[itype],
                                     sd->lb_nobusyg[itype]);
                         }
-                        seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu\n",
+                        seq_printf(seq, " %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
                             sd->alb_cnt, sd->alb_failed, sd->alb_pushed,
-                            sd->sbe_pushed, sd->sbe_attempts,
+                            sd->sbe_cnt, sd->sbe_balanced, sd->sbe_pushed,
+                            sd->sbf_cnt, sd->sbf_balanced, sd->sbf_pushed,
                             sd->ttwu_wake_remote, sd->ttwu_move_affine, sd->ttwu_move_balance);
                 }
 #endif
@@ -1264,24 +1265,34 @@ void fastcall wake_up_new_task(task_t * p, unsigned long clone_flags)
                         sd = tmp;
 
         if (sd) {
+                int new_cpu;
                 struct sched_group *group;
 
+                schedstat_inc(sd, sbf_cnt);
                 cpu = task_cpu(p);
                 group = find_idlest_group(sd, p, cpu);
-                if (group) {
-                        int new_cpu;
-                        new_cpu = find_idlest_cpu(group, cpu);
-                        if (new_cpu != -1 && new_cpu != cpu &&
-                                        cpu_isset(new_cpu, p->cpus_allowed)) {
-                                set_task_cpu(p, new_cpu);
-                                task_rq_unlock(rq, &flags);
-                                rq = task_rq_lock(p, &flags);
-                                cpu = task_cpu(p);
-                        }
+                if (!group) {
+                        schedstat_inc(sd, sbf_balanced);
+                        goto no_forkbalance;
+                }
+
+                new_cpu = find_idlest_cpu(group, cpu);
+                if (new_cpu == -1 || new_cpu == cpu) {
+                        schedstat_inc(sd, sbf_balanced);
+                        goto no_forkbalance;
+                }
+
+                if (cpu_isset(new_cpu, p->cpus_allowed)) {
+                        schedstat_inc(sd, sbf_pushed);
+                        set_task_cpu(p, new_cpu);
+                        task_rq_unlock(rq, &flags);
+                        rq = task_rq_lock(p, &flags);
+                        cpu = task_cpu(p);
                 }
         }
-#endif
 
+no_forkbalance:
+#endif
         /*
          * We decrease the sleep average of forking parents
          * and children as well, to keep max-interactive tasks
@@ -1618,30 +1629,28 @@ void sched_exec(void)
         struct sched_domain *tmp, *sd = NULL;
         int new_cpu, this_cpu = get_cpu();
 
-        /* Prefer the current CPU if there's only this task running */
-        if (this_rq()->nr_running <= 1)
-                goto out;
-
         for_each_domain(this_cpu, tmp)
                 if (tmp->flags & SD_BALANCE_EXEC)
                         sd = tmp;
 
         if (sd) {
                 struct sched_group *group;
-                schedstat_inc(sd, sbe_attempts);
+                schedstat_inc(sd, sbe_cnt);
                 group = find_idlest_group(sd, current, this_cpu);
-                if (!group)
+                if (!group) {
+                        schedstat_inc(sd, sbe_balanced);
                         goto out;
+                }
                 new_cpu = find_idlest_cpu(group, this_cpu);
-                if (new_cpu == -1)
+                if (new_cpu == -1 || new_cpu == this_cpu) {
+                        schedstat_inc(sd, sbe_balanced);
                         goto out;
-
-                if (new_cpu != this_cpu) {
-                        schedstat_inc(sd, sbe_pushed);
-                        put_cpu();
-                        sched_migrate_task(current, new_cpu);
-                        return;
                 }
+
+                schedstat_inc(sd, sbe_pushed);
+                put_cpu();
+                sched_migrate_task(current, new_cpu);
+                return;
         }
 out:
         put_cpu();