sched: Refactor the power savings balance code

Impact: cleanup

Create seperate helper functions to initialize the
power-savings-balance related variables, to update them and
to check if we have a scope for performing power-savings balance.

Add no-op inline functions for the !(CONFIG_SCHED_MC || CONFIG_SCHED_SMT)
case.

This will eliminate all the #ifdef jungle in find_busiest_group() and the
other helper functions.

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>
Cc: "Vaidyanathan Srinivasan" <svaidy@linux.vnet.ibm.com>
LKML-Reference: <20090325091422.13992.73616.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/kernel/sched.c b/kernel/sched.c
index 71e8dcaf2c790eefc3ca429466061e419eb8b9d7..5f21658b0f674f5fb533ecb523a961d8a32d9c30 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3270,6 +3270,151 @@ static inline int get_sd_load_idx(struct sched_domain *sd,
 }
 
 
+#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
+/**
+ * init_sd_power_savings_stats - Initialize power savings statistics for
+ * the given sched_domain, during load balancing.
+ *
+ * @sd: Sched domain whose power-savings statistics are to be initialized.
+ * @sds: Variable containing the statistics for sd.
+ * @idle: Idle status of the CPU at which we're performing load-balancing.
+ */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+       struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+       /*
+        * Busy processors will not participate in power savings
+        * balance.
+        */
+       if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
+               sds->power_savings_balance = 0;
+       else {
+               sds->power_savings_balance = 1;
+               sds->min_nr_running = ULONG_MAX;
+               sds->leader_nr_running = 0;
+       }
+}
+
+/**
+ * update_sd_power_savings_stats - Update the power saving stats for a
+ * sched_domain while performing load balancing.
+ *
+ * @group: sched_group belonging to the sched_domain under consideration.
+ * @sds: Variable containing the statistics of the sched_domain
+ * @local_group: Does group contain the CPU for which we're performing
+ *             load balancing ?
+ * @sgs: Variable containing the statistics of the group.
+ */
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+       struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+
+       if (!sds->power_savings_balance)
+               return;
+
+       /*
+        * If the local group is idle or completely loaded
+        * no need to do power savings balance at this domain
+        */
+       if (local_group && (sds->this_nr_running >= sgs->group_capacity ||
+                               !sds->this_nr_running))
+               sds->power_savings_balance = 0;
+
+       /*
+        * If a group is already running at full capacity or idle,
+        * don't include that group in power savings calculations
+        */
+       if (!sds->power_savings_balance ||
+               sgs->sum_nr_running >= sgs->group_capacity ||
+               !sgs->sum_nr_running)
+               return;
+
+       /*
+        * Calculate the group which has the least non-idle load.
+        * This is the group from where we need to pick up the load
+        * for saving power
+        */
+       if ((sgs->sum_nr_running < sds->min_nr_running) ||
+           (sgs->sum_nr_running == sds->min_nr_running &&
+            group_first_cpu(group) > group_first_cpu(sds->group_min))) {
+               sds->group_min = group;
+               sds->min_nr_running = sgs->sum_nr_running;
+               sds->min_load_per_task = sgs->sum_weighted_load /
+                                               sgs->sum_nr_running;
+       }
+
+       /*
+        * Calculate the group which is almost near its
+        * capacity but still has some space to pick up some load
+        * from other group and save more power
+        */
+       if (sgs->sum_nr_running > sgs->group_capacity - 1)
+               return;
+
+       if (sgs->sum_nr_running > sds->leader_nr_running ||
+           (sgs->sum_nr_running == sds->leader_nr_running &&
+            group_first_cpu(group) < group_first_cpu(sds->group_leader))) {
+               sds->group_leader = group;
+               sds->leader_nr_running = sgs->sum_nr_running;
+       }
+}
+
+/**
+ * check_power_save_busiest_group - Check if we have potential to perform
+ *     some power-savings balance. If yes, set the busiest group to be
+ *     the least loaded group in the sched_domain, so that it's CPUs can
+ *     be put to idle.
+ *
+ * @sds: Variable containing the statistics of the sched_domain
+ *     under consideration.
+ * @this_cpu: Cpu at which we're currently performing load-balancing.
+ * @imbalance: Variable to store the imbalance.
+ *
+ * Returns 1 if there is potential to perform power-savings balance.
+ * Else returns 0.
+ */
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+                                       int this_cpu, unsigned long *imbalance)
+{
+       if (!sds->power_savings_balance)
+               return 0;
+
+       if (sds->this != sds->group_leader ||
+                       sds->group_leader == sds->group_min)
+               return 0;
+
+       *imbalance = sds->min_load_per_task;
+       sds->busiest = sds->group_min;
+
+       if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {
+               cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =
+                       group_first_cpu(sds->group_leader);
+       }
+
+       return 1;
+
+}
+#else /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
+static inline void init_sd_power_savings_stats(struct sched_domain *sd,
+       struct sd_lb_stats *sds, enum cpu_idle_type idle)
+{
+       return;
+}
+
+static inline void update_sd_power_savings_stats(struct sched_group *group,
+       struct sd_lb_stats *sds, int local_group, struct sg_lb_stats *sgs)
+{
+       return;
+}
+
+static inline int check_power_save_busiest_group(struct sd_lb_stats *sds,
+                                       int this_cpu, unsigned long *imbalance)
+{
+       return 0;
+}
+#endif /* CONFIG_SCHED_MC || CONFIG_SCHED_SMT */
+
+
 /**
  * update_sg_lb_stats - Update sched_group's statistics for load balancing.
  * @group: sched_group whose statistics are to be updated.
@@ -3385,19 +3530,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
        struct sg_lb_stats sgs;
        int load_idx;
 
-#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
-       /*
-        * Busy processors will not participate in power savings
-        * balance.
-        */
-       if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
-               sds->power_savings_balance = 0;
-       else {
-               sds->power_savings_balance = 1;
-               sds->min_nr_running = ULONG_MAX;
-               sds->leader_nr_running = 0;
-       }
-#endif
+       init_sd_power_savings_stats(sd, sds, idle);
        load_idx = get_sd_load_idx(sd, idle);
 
        do {
@@ -3430,61 +3563,7 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
                        sds->group_imb = sgs.group_imb;
                }
 
-#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
-
-               if (!sds->power_savings_balance)
-                       goto group_next;
-
-               /*
-                * If the local group is idle or completely loaded
-                * no need to do power savings balance at this domain
-                */
-               if (local_group &&
-                       (sds->this_nr_running >= sgs.group_capacity ||
-                       !sds->this_nr_running))
-                       sds->power_savings_balance = 0;
-
-               /*
-                * If a group is already running at full capacity or idle,
-                * don't include that group in power savings calculations
-                */
-               if (!sds->power_savings_balance ||
-                       sgs.sum_nr_running >= sgs.group_capacity ||
-                       !sgs.sum_nr_running)
-                       goto group_next;
-
-               /*
-                * Calculate the group which has the least non-idle load.
-                * This is the group from where we need to pick up the load
-                * for saving power
-                */
-               if ((sgs.sum_nr_running < sds->min_nr_running) ||
-                   (sgs.sum_nr_running == sds->min_nr_running &&
-                    group_first_cpu(group) >
-                       group_first_cpu(sds->group_min))) {
-                       sds->group_min = group;
-                       sds->min_nr_running = sgs.sum_nr_running;
-                       sds->min_load_per_task = sgs.sum_weighted_load /
-                                               sgs.sum_nr_running;
-               }
-
-               /*
-                * Calculate the group which is almost near its
-                * capacity but still has some space to pick up some load
-                * from other group and save more power
-                */
-               if (sgs.sum_nr_running > sgs.group_capacity - 1)
-                       goto group_next;
-
-               if (sgs.sum_nr_running > sds->leader_nr_running ||
-                   (sgs.sum_nr_running == sds->leader_nr_running &&
-                    group_first_cpu(group) <
-                       group_first_cpu(sds->group_leader))) {
-                       sds->group_leader = group;
-                       sds->leader_nr_running = sgs.sum_nr_running;
-               }
-group_next:
-#endif
+               update_sd_power_savings_stats(group, sds, local_group, &sgs);
                group = group->next;
        } while (group != sd->groups);
 
@@ -3655,21 +3734,12 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
        return sds.busiest;
 
 out_balanced:
-#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
-       if (!sds.power_savings_balance)
-               goto ret;
-
-       if (sds.this != sds.group_leader || sds.group_leader == sds.group_min)
-               goto ret;
-
-       *imbalance = sds.min_load_per_task;
-       if (sched_mc_power_savings >= POWERSAVINGS_BALANCE_WAKEUP) {
-               cpu_rq(this_cpu)->rd->sched_mc_preferred_wakeup_cpu =
-                       group_first_cpu(sds.group_leader);
-       }
-       return sds.group_min;
-
-#endif
+       /*
+        * There is no obvious imbalance. But check if we can do some balancing
+        * to save power.
+        */
+       if (check_power_save_busiest_group(&sds, this_cpu, imbalance))
+               return sds.busiest;
 ret:
        *imbalance = 0;
        return NULL;