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sched: Create a helper function to calculate imbalance

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Move all the imbalance calculation out of find_busiest_group()
through this helper function.

With this change, the structure of find_busiest_group() will be
as follows:

- update_sched_domain_statistics.

- check if imbalance exits.

- update imbalance and return busiest.

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: <20090325091411.13992.43293.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gautham R Shenoy 2009-03-25 14:44:12 +05:30 committed by Ingo Molnar
parent 2e6f44aeda
commit dbc523a3b8
1 changed files with 45 additions and 33 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

78
kernel/sched.c
View File

@ -3487,8 +3487,8 @@ group_next:
/**
* fix_small_imbalance - Calculate the minor imbalance that exists
* amongst the groups of a sched_domain, during
* load balancing.
* 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.
@ -3549,6 +3549,47 @@ static inline void fix_small_imbalance(struct sd_lb_stats *sds,
if (pwr_move > pwr_now)
*imbalance = sds->busiest_load_per_task;
}
/**
* calculate_imbalance - Calculate the amount of imbalance present within the
* groups of a given sched_domain during load balance.
* @sds: statistics of the sched_domain whose imbalance is to be calculated.
* @this_cpu: Cpu for which currently load balance is being performed.
* @imbalance: The variable to store the imbalance.
*/
static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
unsigned long *imbalance)
{
unsigned long max_pull;
/*
* In the presence of smp nice balancing, certain scenarios can have
* max load less than avg load(as we skip the groups at or below
* its cpu_power, while calculating max_load..)
*/
if (sds->max_load < sds->avg_load) {
*imbalance = 0;
return fix_small_imbalance(sds, this_cpu, imbalance);
}
/* Don't want to pull so many tasks that a group would go idle */
max_pull = min(sds->max_load - sds->avg_load,
sds->max_load - sds->busiest_load_per_task);
/* How much load to actually move to equalise the imbalance */
*imbalance = min(max_pull * sds->busiest->__cpu_power,
(sds->avg_load - sds->this_load) * sds->this->__cpu_power)
/ SCHED_LOAD_SCALE;
/*
* if *imbalance is less than the average load per runnable task
* there is no gaurantee that any tasks will be moved so we'll have
* a think about bumping its value to force at least one task to be
* moved
*/
if (*imbalance < sds->busiest_load_per_task)
return fix_small_imbalance(sds, this_cpu, imbalance);
}
/******* find_busiest_group() helpers end here *********************/
/*
@ -3562,7 +3603,6 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
int *sd_idle, const struct cpumask *cpus, int *balance)
{
struct sd_lb_stats sds;
unsigned long max_pull;
memset(&sds, 0, sizeof(sds));
@ -3605,36 +3645,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
if (sds.max_load <= sds.busiest_load_per_task)
goto out_balanced;
/*
* In the presence of smp nice balancing, certain scenarios can have
* max load less than avg load(as we skip the groups at or below
* its cpu_power, while calculating max_load..)
*/
if (sds.max_load < sds.avg_load) {
*imbalance = 0;
fix_small_imbalance(&sds, this_cpu, imbalance);
goto ret_busiest;
}
/* Don't want to pull so many tasks that a group would go idle */
max_pull = min(sds.max_load - sds.avg_load,
sds.max_load - sds.busiest_load_per_task);
/* How much load to actually move to equalise the imbalance */
*imbalance = min(max_pull * sds.busiest->__cpu_power,
(sds.avg_load - sds.this_load) * sds.this->__cpu_power)
/ SCHED_LOAD_SCALE;
/*
* if *imbalance is less than the average load per runnable task
* there is no gaurantee that any tasks will be moved so we'll have
* a think about bumping its value to force at least one task to be
* moved
*/
if (*imbalance < sds.busiest_load_per_task)
fix_small_imbalance(&sds, this_cpu, imbalance);
ret_busiest:
/* Looks like there is an imbalance. Compute it */
calculate_imbalance(&sds, this_cpu, imbalance);
return sds.busiest;
out_balanced: