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>

1 files changed, 13 insertions, 15 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index cd18600a8a63..03496ebc4553 100644
--- 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;