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Subject[RFC PATCH 04/11] sched: Create a helper function to calculate sched_group stats for fbg()
Date
Create a helper function named update_sg_lb_stats() which can be invoked to
calculate the individual group's statistics in find_busiest_group().

This reduces the lenght of find_busiest_group() considerably.

Credit: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
---

kernel/sched.c | 175 ++++++++++++++++++++++++++++++++------------------------
1 files changed, 100 insertions(+), 75 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index 6da9939..d2e9b8a 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3133,6 +3133,103 @@ static inline int get_sd_load_idx(struct sched_domain *sd,

return load_idx;
}
+
+
+/**
+ * update_sg_lb_stats - Update sched_group's statistics for load balancing.
+ * @group: sched_group whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @load_idx: Load index of sched_domain of this_cpu for load calc.
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @local_group: Does group contain this_cpu.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sgs: variable to hold the statistics for this group.
+ */
+static inline void update_sg_lb_stats(struct sched_group *group, int this_cpu,
+ enum cpu_idle_type idle, int load_idx, int *sd_idle,
+ int local_group, const struct cpumask *cpus,
+ int *balance, struct sg_lb_stats *sgs)
+{
+ unsigned long load, max_cpu_load, min_cpu_load;
+ int i;
+ unsigned int balance_cpu = -1, first_idle_cpu = 0;
+ unsigned long sum_avg_load_per_task;
+ unsigned long avg_load_per_task;
+
+ if (local_group)
+ balance_cpu = group_first_cpu(group);
+
+ /* Tally up the load of all CPUs in the group */
+ sum_avg_load_per_task = avg_load_per_task = 0;
+ max_cpu_load = 0;
+ min_cpu_load = ~0UL;
+
+ for_each_cpu_and(i, sched_group_cpus(group), cpus) {
+ struct rq *rq = cpu_rq(i);
+
+ if (*sd_idle && rq->nr_running)
+ *sd_idle = 0;
+
+ /* Bias balancing toward cpus of our domain */
+ if (local_group) {
+ if (idle_cpu(i) && !first_idle_cpu) {
+ first_idle_cpu = 1;
+ balance_cpu = i;
+ }
+
+ load = target_load(i, load_idx);
+ } else {
+ load = source_load(i, load_idx);
+ if (load > max_cpu_load)
+ max_cpu_load = load;
+ if (min_cpu_load > load)
+ min_cpu_load = load;
+ }
+
+ sgs->group_load += load;
+ sgs->sum_nr_running += rq->nr_running;
+ sgs->sum_weighted_load += weighted_cpuload(i);
+
+ sum_avg_load_per_task += cpu_avg_load_per_task(i);
+ }
+
+ /*
+ * First idle cpu or the first cpu(busiest) in this sched group
+ * is eligible for doing load balancing at this and above
+ * domains. In the newly idle case, we will allow all the cpu's
+ * to do the newly idle load balance.
+ */
+ if (idle != CPU_NEWLY_IDLE && local_group &&
+ balance_cpu != this_cpu && balance) {
+ *balance = 0;
+ return;
+ }
+
+ /* Adjust by relative CPU power of the group */
+ sgs->avg_load = sg_div_cpu_power(group,
+ sgs->group_load * SCHED_LOAD_SCALE);
+
+
+ /*
+ * Consider the group unbalanced when the imbalance is larger
+ * than the average weight of two tasks.
+ *
+ * APZ: with cgroup the avg task weight can vary wildly and
+ * might not be a suitable number - should we keep a
+ * normalized nr_running number somewhere that negates
+ * the hierarchy?
+ */
+ avg_load_per_task = sg_div_cpu_power(group,
+ sum_avg_load_per_task * SCHED_LOAD_SCALE);
+
+ if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
+ sgs->group_imb = 1;
+
+ sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
+
+}
/******* find_busiest_group() helpers end here *********************/

/*
@@ -3166,92 +3263,20 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,

do {
struct sg_lb_stats sgs;
- unsigned long load, max_cpu_load, min_cpu_load;
int local_group;
- int i;
- unsigned int balance_cpu = -1, first_idle_cpu = 0;
- unsigned long sum_avg_load_per_task;
- unsigned long avg_load_per_task;

local_group = cpumask_test_cpu(this_cpu,
sched_group_cpus(group));
memset(&sgs, 0, sizeof(sgs));
+ update_sg_lb_stats(group, this_cpu, idle, load_idx, sd_idle,
+ local_group, cpus, balance, &sgs);

- if (local_group)
- balance_cpu = group_first_cpu(group);
-
- /* Tally up the load of all CPUs in the group */
- sum_avg_load_per_task = avg_load_per_task = 0;
-
- max_cpu_load = 0;
- min_cpu_load = ~0UL;
-
- for_each_cpu_and(i, sched_group_cpus(group), cpus) {
- struct rq *rq = cpu_rq(i);
-
- if (*sd_idle && rq->nr_running)
- *sd_idle = 0;
-
- /* Bias balancing toward cpus of our domain */
- if (local_group) {
- if (idle_cpu(i) && !first_idle_cpu) {
- first_idle_cpu = 1;
- balance_cpu = i;
- }
-
- load = target_load(i, load_idx);
- } else {
- load = source_load(i, load_idx);
- if (load > max_cpu_load)
- max_cpu_load = load;
- if (min_cpu_load > load)
- min_cpu_load = load;
- }
-
- sgs.group_load += load;
- sgs.sum_nr_running += rq->nr_running;
- sgs.sum_weighted_load += weighted_cpuload(i);
-
- sum_avg_load_per_task += cpu_avg_load_per_task(i);
- }
-
- /*
- * First idle cpu or the first cpu(busiest) in this sched group
- * is eligible for doing load balancing at this and above
- * domains. In the newly idle case, we will allow all the cpu's
- * to do the newly idle load balance.
- */
- if (idle != CPU_NEWLY_IDLE && local_group &&
- balance_cpu != this_cpu && balance) {
- *balance = 0;
+ if (balance && !(*balance))
goto ret;
- }

total_load += sgs.group_load;
total_pwr += group->__cpu_power;

- /* Adjust by relative CPU power of the group */
- sgs.avg_load = sg_div_cpu_power(group,
- sgs.group_load * SCHED_LOAD_SCALE);
-
-
- /*
- * Consider the group unbalanced when the imbalance is larger
- * than the average weight of two tasks.
- *
- * APZ: with cgroup the avg task weight can vary wildly and
- * might not be a suitable number - should we keep a
- * normalized nr_running number somewhere that negates
- * the hierarchy?
- */
- avg_load_per_task = sg_div_cpu_power(group,
- sum_avg_load_per_task * SCHED_LOAD_SCALE);
-
- if ((max_cpu_load - min_cpu_load) > 2*avg_load_per_task)
- sgs.group_imb = 1;
-
- sgs.group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;
-
if (local_group) {
this_load = sgs.avg_load;
this = group;


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