sched: Clean up some f_b_g() comments

The existing comment tends to grow state (as it already has), split it
up and place it near the actual tests.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nikhil Rao <ncrao@google.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index cd18600..03496eb 100644 (file)
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -3113,19 +3113,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
         */
        update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds);
 
-       /* Cases where imbalance does not exist from POV of this_cpu */
-       /* 1) this_cpu is not the appropriate cpu to perform load balancing
-        *    at this level.
-        * 2) There is no busy sibling group to pull from.
-        * 3) This group is the busiest group.
-        * 4) This group is more busy than the avg busieness at this
-        *    sched_domain.
-        * 5) The imbalance is within the specified limit.
-        *
-        * Note: when doing newidle balance, if the local group has excess
-        * capacity (i.e. nr_running < group_capacity) and the busiest group
-        * does not have any capacity, we force a load balance to pull tasks
-        * to the local group. In this case, we skip past checks 3, 4 and 5.
+       /*
+        * this_cpu is not the appropriate cpu to perform load balancing at
+        * this level.
         */
        if (!(*balance))
                goto ret;
@@ -3134,19 +3124,27 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
            check_asym_packing(sd, &sds, this_cpu, imbalance))
                return sds.busiest;
 
+       /* There is no busy sibling group to pull tasks from */
        if (!sds.busiest || sds.busiest_nr_running == 0)
                goto out_balanced;
 
-       /*  SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
+       /* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
        if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
                        !sds.busiest_has_capacity)
                goto force_balance;
 
+       /*
+        * If the local group is more busy than the selected busiest group
+        * don't try and pull any tasks.
+        */
        if (sds.this_load >= sds.max_load)
                goto out_balanced;
 
+       /*
+        * Don't pull any tasks if this group is already above the domain
+        * average load.
+        */
        sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
-
        if (sds.this_load >= sds.avg_load)
                goto out_balanced;