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sched: Optimize the !power_savings_balance during fbg()

Browse source 
Impact: cleanup, micro-optimization

We don't need to perform power_savings balance if either the
cpu is NOT_IDLE or if the sched_domain doesn't contain the
SD_POWERSAVINGS_BALANCE flag set.

Currently, we check for these conditions multiple number of
times, even though these variables don't change over the scope
of find_busiest_group().

Check once, and store the value in the already exiting
"power_savings_balance" variable.

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: <20090325091417.13992.2657.stgit@sofia.in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Gautham R Shenoy 2009-03-25 14:44:17 +05:30 committed by Ingo Molnar
parent dbc523a3b8
commit a021dc0337
1 changed files with 14 additions and 9 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

23
kernel/sched.c
View file

@ -3386,8 +3386,17 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
int load_idx;
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
sds->power_savings_balance = 1;
sds->min_nr_running = ULONG_MAX;
/*
* Busy processors will not participate in power savings
* balance.
*/
if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
sds->power_savings_balance = 0;
else {
sds->power_savings_balance = 1;
sds->min_nr_running = ULONG_MAX;
sds->leader_nr_running = 0;
}
#endif
load_idx = get_sd_load_idx(sd, idle);
@ -3422,12 +3431,8 @@ static inline void update_sd_lb_stats(struct sched_domain *sd, int this_cpu,
}
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
/*
* Busy processors will not participate in power savings
* balance.
*/
if (idle == CPU_NOT_IDLE ||
!(sd->flags & SD_POWERSAVINGS_BALANCE))
if (!sds->power_savings_balance)
goto group_next;
/*
@ -3651,7 +3656,7 @@ find_busiest_group(struct sched_domain *sd, int this_cpu,
out_balanced:
#if defined(CONFIG_SCHED_MC) || defined(CONFIG_SCHED_SMT)
if (idle == CPU_NOT_IDLE || !(sd->flags & SD_POWERSAVINGS_BALANCE))
if (!sds.power_savings_balance)
goto ret;
if (sds.this != sds.group_leader || sds.group_leader == sds.group_min)