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sched: Create helper to calculate small_imbalance in fbg()

Browse source 
Impact: cleanup

We have two places in find_busiest_group() where we need to calculate
the minor imbalance before returning the busiest group. Encapsulate
this functionality into a seperate helper function.

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: <20090325091406.13992.54316.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gautham R Shenoy 2009-03-25 14:44:06 +05:30 committed by Ingo Molnar
parent 37abe198b1
commit 2e6f44aeda
1 changed files with 70 additions and 61 deletions
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131
kernel/sched.c
View file

@ -3484,6 +3484,71 @@ group_next:
} while (group != sd->groups);
}
/**
* fix_small_imbalance - Calculate the minor imbalance that exists
* 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.
*/
static inline void fix_small_imbalance(struct sd_lb_stats *sds,
int this_cpu, unsigned long *imbalance)
{
unsigned long tmp, pwr_now = 0, pwr_move = 0;
unsigned int imbn = 2;
if (sds->this_nr_running) {
sds->this_load_per_task /= sds->this_nr_running;
if (sds->busiest_load_per_task >
sds->this_load_per_task)
imbn = 1;
} else
sds->this_load_per_task =
cpu_avg_load_per_task(this_cpu);
if (sds->max_load - sds->this_load + sds->busiest_load_per_task >=
sds->busiest_load_per_task * imbn) {
*imbalance = sds->busiest_load_per_task;
return;
}
/*
* OK, we don't have enough imbalance to justify moving tasks,
* however we may be able to increase total CPU power used by
* moving them.
*/
pwr_now += sds->busiest->__cpu_power *
min(sds->busiest_load_per_task, sds->max_load);
pwr_now += sds->this->__cpu_power *
min(sds->this_load_per_task, sds->this_load);
pwr_now /= SCHED_LOAD_SCALE;
/* Amount of load we'd subtract */
tmp = sg_div_cpu_power(sds->busiest,
sds->busiest_load_per_task * SCHED_LOAD_SCALE);
if (sds->max_load > tmp)
pwr_move += sds->busiest->__cpu_power *
min(sds->busiest_load_per_task, sds->max_load - tmp);
/* Amount of load we'd add */
if (sds->max_load * sds->busiest->__cpu_power <
sds->busiest_load_per_task * SCHED_LOAD_SCALE)
tmp = sg_div_cpu_power(sds->this,
sds->max_load * sds->busiest->__cpu_power);
else
tmp = sg_div_cpu_power(sds->this,
sds->busiest_load_per_task * SCHED_LOAD_SCALE);
pwr_move += sds->this->__cpu_power *
min(sds->this_load_per_task, sds->this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain throughput */
if (pwr_move > pwr_now)
*imbalance = sds->busiest_load_per_task;
}
/******* find_busiest_group() helpers end here *********************/
/*
@ -3547,7 +3612,8 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
*/
if (sds.max_load < sds.avg_load) {
*imbalance = 0;
goto small_imbalance;
fix_small_imbalance(&sds, this_cpu, imbalance);
goto ret_busiest;
}
/* Don't want to pull so many tasks that a group would go idle */
@ -3565,67 +3631,10 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
* a think about bumping its value to force at least one task to be
* moved
*/
if (*imbalance < sds.busiest_load_per_task) {
unsigned long tmp, pwr_now, pwr_move;
unsigned int imbn;
small_imbalance:
pwr_move = pwr_now = 0;
imbn = 2;
if (sds.this_nr_running) {
sds.this_load_per_task /= sds.this_nr_running;
if (sds.busiest_load_per_task >
sds.this_load_per_task)
imbn = 1;
} else
sds.this_load_per_task =
cpu_avg_load_per_task(this_cpu);
if (sds.max_load - sds.this_load +
sds.busiest_load_per_task >=
sds.busiest_load_per_task * imbn) {
*imbalance = sds.busiest_load_per_task;
return sds.busiest;
}
/*
* OK, we don't have enough imbalance to justify moving tasks,
* however we may be able to increase total CPU power used by
* moving them.
*/
pwr_now += sds.busiest->__cpu_power *
min(sds.busiest_load_per_task, sds.max_load);
pwr_now += sds.this->__cpu_power *
min(sds.this_load_per_task, sds.this_load);
pwr_now /= SCHED_LOAD_SCALE;
/* Amount of load we'd subtract */
tmp = sg_div_cpu_power(sds.busiest,
sds.busiest_load_per_task * SCHED_LOAD_SCALE);
if (sds.max_load > tmp)
pwr_move += sds.busiest->__cpu_power *
min(sds.busiest_load_per_task,
sds.max_load - tmp);
/* Amount of load we'd add */
if (sds.max_load * sds.busiest->__cpu_power <
sds.busiest_load_per_task * SCHED_LOAD_SCALE)
tmp = sg_div_cpu_power(sds.this,
sds.max_load * sds.busiest->__cpu_power);
else
tmp = sg_div_cpu_power(sds.this,
sds.busiest_load_per_task * SCHED_LOAD_SCALE);
pwr_move += sds.this->__cpu_power *
min(sds.this_load_per_task,
sds.this_load + tmp);
pwr_move /= SCHED_LOAD_SCALE;
/* Move if we gain throughput */
if (pwr_move > pwr_now)
*imbalance = sds.busiest_load_per_task;
}
if (*imbalance < sds.busiest_load_per_task)
fix_small_imbalance(&sds, this_cpu, imbalance);
ret_busiest:
return sds.busiest;
out_balanced: