sched: Add comments to find_busiest_group() function
Impact: cleanup Add /** style comments around find_busiest_group(). Also add a few explanatory comments. This concludes the find_busiest_group() cleanup. The function is now down to 72 lines from the original 313 lines. 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: <20090325091427.13992.18933.stgit@sofia.in.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
parent
c071df1852
commit
b7bb4c9bb0
|
@ -3676,10 +3676,30 @@ static inline void calculate_imbalance(struct sd_lb_stats *sds, int this_cpu,
|
|||
}
|
||||
/******* 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.
|
||||
/**
|
||||
* find_busiest_group - Returns the busiest group within the sched_domain
|
||||
* if there is an imbalance. If there isn't an imbalance, and
|
||||
* the user has opted for power-savings, it returns a group whose
|
||||
* CPUs can be put to idle by rebalancing those tasks elsewhere, if
|
||||
* such a group exists.
|
||||
*
|
||||
* Also calculates the amount of weighted load which should be moved
|
||||
* to restore balance.
|
||||
*
|
||||
* @sd: The sched_domain whose busiest group is to be returned.
|
||||
* @this_cpu: The cpu for which load balancing is currently being performed.
|
||||
* @imbalance: Variable which stores amount of weighted load which should
|
||||
* be moved to restore balance/put a group to idle.
|
||||
* @idle: The idle status of this_cpu.
|
||||
* @sd_idle: The idleness of sd
|
||||
* @cpus: The set of CPUs under consideration for load-balancing.
|
||||
* @balance: Pointer to a variable indicating if this_cpu
|
||||
* is the appropriate cpu to perform load balancing at this_level.
|
||||
*
|
||||
* Returns: - the busiest group if imbalance exists.
|
||||
* - If no imbalance and user has opted for power-savings balance,
|
||||
* return the least loaded group whose CPUs can be
|
||||
* put to idle by rebalancing its tasks onto our group.
|
||||
*/
|
||||
static struct sched_group *
|
||||
find_busiest_group(struct sched_domain *sd, int this_cpu,
|
||||
|
@ -3697,17 +3717,31 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
|
|||
update_sd_lb_stats(sd, this_cpu, idle, sd_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.
|
||||
* 6) Any rebalance would lead to ping-pong
|
||||
*/
|
||||
if (balance && !(*balance))
|
||||
goto ret;
|
||||
|
||||
if (!sds.busiest || sds.this_load >= sds.max_load
|
||||
|| sds.busiest_nr_running == 0)
|
||||
if (!sds.busiest || sds.busiest_nr_running == 0)
|
||||
goto out_balanced;
|
||||
|
||||
if (sds.this_load >= sds.max_load)
|
||||
goto out_balanced;
|
||||
|
||||
sds.avg_load = (SCHED_LOAD_SCALE * sds.total_load) / sds.total_pwr;
|
||||
|
||||
if (sds.this_load >= sds.avg_load ||
|
||||
100*sds.max_load <= sd->imbalance_pct * sds.this_load)
|
||||
if (sds.this_load >= sds.avg_load)
|
||||
goto out_balanced;
|
||||
|
||||
if (100 * sds.max_load <= sd->imbalance_pct * sds.this_load)
|
||||
goto out_balanced;
|
||||
|
||||
sds.busiest_load_per_task /= sds.busiest_nr_running;
|
||||
|
|
Loading…
Reference in a new issue