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>

1 files changed, 153 insertions, 83 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 71e8dcaf2c79..5f21658b0f67 100644
--- 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;