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sched: Clean up some f_b_g() comments 

The existing comment tends to grow state (as it already has), split it
up and place it near the actual tests.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Nikhil Rao <ncrao@google.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2011-02-21 18:55:32 +01:00 committed by Ingo Molnar
parent c186fafe9a
commit cc57aa8f4b
1 changed files with 13 additions and 15 deletions
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28
kernel/sched_fair.c
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@ -3113,19 +3113,9 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
*/
update_sd_lb_stats(sd, this_cpu, idle, cpus, balance, &sds);
/* Cases where imbalance does not exist from POV of this_cpu */
/* 1) this_cpu is not the appropriate cpu to perform load balancing
* at this level.
* 2) There is no busy sibling group to pull from.
* 3) This group is the busiest group.
* 4) This group is more busy than the avg busieness at this
* sched_domain.
* 5) The imbalance is within the specified limit.
*
* Note: when doing newidle balance, if the local group has excess
* capacity (i.e. nr_running < group_capacity) and the busiest group
* does not have any capacity, we force a load balance to pull tasks
* to the local group. In this case, we skip past checks 3, 4 and 5.
/*
* this_cpu is not the appropriate cpu to perform load balancing at
* this level.
*/
if (!(*balance))
goto ret;
@ -3134,19 +3124,27 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
check_asym_packing(sd, &sds, this_cpu, imbalance))
return sds.busiest;
/* There is no busy sibling group to pull tasks from */
if (!sds.busiest || sds.busiest_nr_running == 0)
goto out_balanced;
/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
/* SD_BALANCE_NEWIDLE trumps SMP nice when underutilized */
if (idle == CPU_NEWLY_IDLE && sds.this_has_capacity &&
!sds.busiest_has_capacity)
goto force_balance;
/*
* If the local group is more busy than the selected busiest group
* don't try and pull any tasks.
*/
if (sds.this_load >= sds.max_load)
goto out_balanced;
/*
* Don't pull any tasks if this group is already above the domain
* average load.
*/
sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
if (sds.this_load >= sds.avg_load)
goto out_balanced;