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Subject[tip:sched/balancing] sched: Create a helper function to calculate sched_domain stats for fbg()
Commit-ID:  37abe198b1246ddd206319c43502a687db62d347
Gitweb: http://git.kernel.org/tip/37abe198b1246ddd206319c43502a687db62d347
Author: Gautham R Shenoy <ego@in.ibm.com>
AuthorDate: Wed, 25 Mar 2009 14:44:01 +0530
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Wed, 25 Mar 2009 10:30:46 +0100

sched: Create a helper function to calculate sched_domain stats for fbg()

Impact: cleanup

Create a helper function named update_sd_lb_stats() to update the
various sched_domain related statistics in find_busiest_group().

With this we would have moved all the statistics computation out of
find_busiest_group().

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: <20090325091401.13992.88737.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>


---
kernel/sched.c | 117 +++++++++++++++++++++++++++++++++++---------------------
1 files changed, 73 insertions(+), 44 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index 8198dbe..ec715f9 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -3365,32 +3365,33 @@ static inline void update_sg_lb_stats(struct sched_group *group, int this_cpu,
sgs->group_capacity = group->__cpu_power / SCHED_LOAD_SCALE;

}
-/******* find_busiest_group() helpers end here *********************/

-/*
- * find_busiest_group finds and returns the busiest CPU group within the
- * domain. It calculates and returns the amount of weighted load which
- * should be moved to restore balance via the imbalance parameter.
+/**
+ * update_sd_lb_stats - Update sched_group's statistics for load balancing.
+ * @sd: sched_domain whose statistics are to be updated.
+ * @this_cpu: Cpu for which load balance is currently performed.
+ * @idle: Idle status of this_cpu
+ * @sd_idle: Idle status of the sched_domain containing group.
+ * @cpus: Set of cpus considered for load balancing.
+ * @balance: Should we balance.
+ * @sds: variable to hold the statistics for this sched_domain.
*/
-static struct sched_group *
-find_busiest_group(struct sched_domain *sd, int this_cpu,
- unsigned long *imbalance, enum cpu_idle_type idle,
- int *sd_idle, const struct cpumask *cpus, int *balance)
+static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
+ enum cpu_idle_type idle, int *sd_idle,
+ const struct cpumask *cpus, int *balance,
+ struct sd_lb_stats *sds)
{
- struct sd_lb_stats sds;
struct sched_group *group = sd->groups;
- unsigned long max_pull;
+ struct sg_lb_stats sgs;
int load_idx;

- memset(&sds, 0, sizeof(sds));
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
- sds.power_savings_balance = 1;
- sds.min_nr_running = ULONG_MAX;
+ sds->power_savings_balance = 1;
+ sds->min_nr_running = ULONG_MAX;
#endif
load_idx = get_sd_load_idx(sd, idle);

do {
- struct sg_lb_stats sgs;
int local_group;

local_group = cpumask_test_cpu(this_cpu,
@@ -3399,25 +3400,25 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
update_sg_lb_stats(group, this_cpu, idle, load_idx, sd_idle,
local_group, cpus, balance, &sgs);

- if (balance && !(*balance))
- goto ret;
+ if (local_group && balance && !(*balance))
+ return;

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

if (local_group) {
- sds.this_load = sgs.avg_load;
- sds.this = group;
- sds.this_nr_running = sgs.sum_nr_running;
- sds.this_load_per_task = sgs.sum_weighted_load;
- } else if (sgs.avg_load > sds.max_load &&
+ sds->this_load = sgs.avg_load;
+ sds->this = group;
+ sds->this_nr_running = sgs.sum_nr_running;
+ sds->this_load_per_task = sgs.sum_weighted_load;
+ } else if (sgs.avg_load > sds->max_load &&
(sgs.sum_nr_running > sgs.group_capacity ||
sgs.group_imb)) {
- sds.max_load = sgs.avg_load;
- sds.busiest = group;
- sds.busiest_nr_running = sgs.sum_nr_running;
- sds.busiest_load_per_task = sgs.sum_weighted_load;
- sds.group_imb = sgs.group_imb;
+ sds->max_load = sgs.avg_load;
+ sds->busiest = group;
+ sds->busiest_nr_running = sgs.sum_nr_running;
+ sds->busiest_load_per_task = sgs.sum_weighted_load;
+ sds->group_imb = sgs.group_imb;
}

#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
@@ -3434,15 +3435,15 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
* 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;
+ (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 ||
+ if (!sds->power_savings_balance ||
sgs.sum_nr_running >= sgs.group_capacity ||
!sgs.sum_nr_running)
goto group_next;
@@ -3452,13 +3453,13 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
* 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 &&
+ 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 /
+ 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;
}

@@ -3470,18 +3471,46 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
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 &&
+ 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_first_cpu(sds->group_leader))) {
+ sds->group_leader = group;
+ sds->leader_nr_running = sgs.sum_nr_running;
}
group_next:
#endif
group = group->next;
} while (group != sd->groups);

+}
+/******* find_busiest_group() helpers end here *********************/
+
+/*
+ * find_busiest_group finds and returns the busiest CPU group within the
+ * domain. It calculates and returns the amount of weighted load which
+ * should be moved to restore balance via the imbalance parameter.
+ */
+static struct sched_group *
+find_busiest_group(struct sched_domain *sd, int this_cpu,
+ unsigned long *imbalance, enum cpu_idle_type idle,
+ int *sd_idle, const struct cpumask *cpus, int *balance)
+{
+ struct sd_lb_stats sds;
+ unsigned long max_pull;
+
+ memset(&sds, 0, sizeof(sds));
+
+ /*
+ * Compute the various statistics relavent for load balancing at
+ * this level.
+ */
+ update_sd_lb_stats(sd, this_cpu, idle, sd_idle, cpus,
+ balance, &sds);
+
+ if (balance && !(*balance))
+ goto ret;
+
if (!sds.busiest || sds.this_load >= sds.max_load
|| sds.busiest_nr_running == 0)
goto out_balanced;

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