sched: Create helper to calculate small_imbalance in fbg()

Impact: cleanup

We have two places in find_busiest_group() where we need to calculate
the minor imbalance before returning the busiest group. Encapsulate
this functionality into a seperate helper function.

Credit: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: "Balbir Singh" <balbir@in.ibm.com>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: "Dhaval Giani" <dhaval@linux.vnet.ibm.com>
Cc: Bharata B Rao <bharata@linux.vnet.ibm.com>
LKML-Reference: <20090325091406.13992.54316.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 70 insertions, 61 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index ec715f97202e..540147e5e82b 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3484,6 +3484,71 @@ group_next:
         } while (group != sd->groups);
 
 }
+
+/**
+ * fix_small_imbalance - Calculate the minor imbalance that exists
+ *                      amongst the groups of a sched_domain, during
+ *                      load balancing.
+ * @sds: Statistics of the sched_domain whose imbalance is to be calculated.
+ * @this_cpu: The cpu at whose sched_domain we're performing load-balance.
+ * @imbalance: Variable to store the imbalance.
+ */
+static inline void fix_small_imbalance(struct sd_lb_stats *sds,
+                                int this_cpu, unsigned long *imbalance)
+{
+        unsigned long tmp, pwr_now = 0, pwr_move = 0;
+        unsigned int imbn = 2;
+
+        if (sds->this_nr_running) {
+                sds->this_load_per_task /= sds->this_nr_running;
+                if (sds->busiest_load_per_task >
+                                sds->this_load_per_task)
+                        imbn = 1;
+        } else
+                sds->this_load_per_task =
+                        cpu_avg_load_per_task(this_cpu);
+
+        if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
+                        sds->busiest_load_per_task * imbn) {
+                *imbalance = sds->busiest_load_per_task;
+                return;
+        }
+
+        /*
+         * OK, we don't have enough imbalance to justify moving tasks,
+         * however we may be able to increase total CPU power used by
+         * moving them.
+         */
+
+        pwr_now += sds->busiest->__cpu_power *
+                        min(sds->busiest_load_per_task, sds->max_load);
+        pwr_now += sds->this->__cpu_power *
+                        min(sds->this_load_per_task, sds->this_load);
+        pwr_now /= SCHED_LOAD_SCALE;
+
+        /* Amount of load we'd subtract */
+        tmp = sg_div_cpu_power(sds->busiest,
+                        sds->busiest_load_per_task * SCHED_LOAD_SCALE);
+        if (sds->max_load > tmp)
+                pwr_move += sds->busiest->__cpu_power *
+                        min(sds->busiest_load_per_task, sds->max_load - tmp);
+
+        /* Amount of load we'd add */
+        if (sds->max_load * sds->busiest->__cpu_power <
+                sds->busiest_load_per_task * SCHED_LOAD_SCALE)
+                tmp = sg_div_cpu_power(sds->this,
+                        sds->max_load * sds->busiest->__cpu_power);
+        else
+                tmp = sg_div_cpu_power(sds->this,
+                        sds->busiest_load_per_task * SCHED_LOAD_SCALE);
+        pwr_move += sds->this->__cpu_power *
+                        min(sds->this_load_per_task, sds->this_load + tmp);
+        pwr_move /= SCHED_LOAD_SCALE;
+
+        /* Move if we gain throughput */
+        if (pwr_move > pwr_now)
+                *imbalance = sds->busiest_load_per_task;
+}
 /******* find_busiest_group() helpers end here *********************/
 
 /*
@@ -3547,7 +3612,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
          */
         if (sds.max_load < sds.avg_load) {
                 *imbalance = 0;
-                goto small_imbalance;
+                fix_small_imbalance(&sds, this_cpu, imbalance);
+                goto ret_busiest;
         }
 
         /* Don't want to pull so many tasks that a group would go idle */
@@ -3565,67 +3631,10 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
          * a think about bumping its value to force at least one task to be
          * moved
          */
-        if (*imbalance < sds.busiest_load_per_task) {
-                unsigned long tmp, pwr_now, pwr_move;
-                unsigned int imbn;
-
-small_imbalance:
-                pwr_move = pwr_now = 0;
-                imbn = 2;
-                if (sds.this_nr_running) {
-                        sds.this_load_per_task /= sds.this_nr_running;
-                        if (sds.busiest_load_per_task >
-                                        sds.this_load_per_task)
-                                imbn = 1;
-                } else
-                        sds.this_load_per_task =
-                                cpu_avg_load_per_task(this_cpu);
-
-                if (sds.max_load - sds.this_load +
-                        sds.busiest_load_per_task >=
-                                sds.busiest_load_per_task * imbn) {
-                        *imbalance = sds.busiest_load_per_task;
-                        return sds.busiest;
-                }
-
-                /*
-                 * OK, we don't have enough imbalance to justify moving tasks,
-                 * however we may be able to increase total CPU power used by
-                 * moving them.
-                 */
-
-                pwr_now += sds.busiest->__cpu_power *
-                                min(sds.busiest_load_per_task, sds.max_load);
-                pwr_now += sds.this->__cpu_power *
-                                min(sds.this_load_per_task, sds.this_load);
-                pwr_now /= SCHED_LOAD_SCALE;
-
-                /* Amount of load we'd subtract */
-                tmp = sg_div_cpu_power(sds.busiest,
-                                sds.busiest_load_per_task * SCHED_LOAD_SCALE);
-                if (sds.max_load > tmp)
-                        pwr_move += sds.busiest->__cpu_power *
-                                min(sds.busiest_load_per_task,
-                                                sds.max_load - tmp);
-
-                /* Amount of load we'd add */
-                if (sds.max_load * sds.busiest->__cpu_power <
-                                sds.busiest_load_per_task * SCHED_LOAD_SCALE)
-                        tmp = sg_div_cpu_power(sds.this,
-                                sds.max_load * sds.busiest->__cpu_power);
-                else
-                        tmp = sg_div_cpu_power(sds.this,
-                                sds.busiest_load_per_task * SCHED_LOAD_SCALE);
-                pwr_move += sds.this->__cpu_power *
-                                min(sds.this_load_per_task,
-                                        sds.this_load + tmp);
-                pwr_move /= SCHED_LOAD_SCALE;
-
-                /* Move if we gain throughput */
-                if (pwr_move > pwr_now)
-                        *imbalance = sds.busiest_load_per_task;
-        }
+        if (*imbalance < sds.busiest_load_per_task)
+                fix_small_imbalance(&sds, this_cpu, imbalance);
 
+ret_busiest:
         return sds.busiest;
 
 out_balanced: