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sched: minor optimizations in wake_affine and select_task_rq_fair

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This patch does following:
o Removes unused variable and argument "rq".
o Optimizes one of the "if" conditions in wake_affine() - i.e.  if
  "balanced" is true, we need not do rest of the calculations in the
  condition.
o If this cpu is same as the previous cpu (on which woken up task
  was running when it went to sleep), no need to call wake_affine at all.

Signed-off-by: Amit K Arora <aarora@linux.vnet.ibm.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Amit K. Arora 2008-09-30 17:15:39 +05:30 committed by Ingo Molnar
parent b87f17242d
commit 64b9e0294d
1 changed files with 7 additions and 9 deletions
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16
kernel/sched_fair.c
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@ -1088,7 +1088,7 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu,
#endif #endif
static int static int
wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq, wake_affine(struct sched_domain *this_sd, struct rq *this_rq,
struct task_struct *p, int prev_cpu, int this_cpu, int sync, struct task_struct *p, int prev_cpu, int this_cpu, int sync,
int idx, unsigned long load, unsigned long this_load, int idx, unsigned long load, unsigned long this_load,
unsigned int imbalance) unsigned int imbalance)
@ -1136,8 +1136,8 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq,
schedstat_inc(p, se.nr_wakeups_affine_attempts); schedstat_inc(p, se.nr_wakeups_affine_attempts);
tl_per_task = cpu_avg_load_per_task(this_cpu); tl_per_task = cpu_avg_load_per_task(this_cpu);
if ((tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task) || if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=
balanced) { tl_per_task)) {
/* /*
* This domain has SD_WAKE_AFFINE and * This domain has SD_WAKE_AFFINE and
* p is cache cold in this domain, and * p is cache cold in this domain, and
@ -1156,16 +1156,17 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
struct sched_domain *sd, *this_sd = NULL; struct sched_domain *sd, *this_sd = NULL;
int prev_cpu, this_cpu, new_cpu; int prev_cpu, this_cpu, new_cpu;
unsigned long load, this_load; unsigned long load, this_load;
struct rq *rq, *this_rq; struct rq *this_rq;
unsigned int imbalance; unsigned int imbalance;
int idx; int idx;
prev_cpu = task_cpu(p); prev_cpu = task_cpu(p);
rq = task_rq(p);
this_cpu = smp_processor_id(); this_cpu = smp_processor_id();
this_rq = cpu_rq(this_cpu); this_rq = cpu_rq(this_cpu);
new_cpu = prev_cpu; new_cpu = prev_cpu;
if (prev_cpu == this_cpu)
goto out;
/* /*
* 'this_sd' is the first domain that both * 'this_sd' is the first domain that both
* this_cpu and prev_cpu are present in: * this_cpu and prev_cpu are present in:
@ -1193,13 +1194,10 @@ static int select_task_rq_fair(struct task_struct *p, int sync)
load = source_load(prev_cpu, idx); load = source_load(prev_cpu, idx);
this_load = target_load(this_cpu, idx); this_load = target_load(this_cpu, idx);
if (wake_affine(rq, this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx, if (wake_affine(this_sd, this_rq, p, prev_cpu, this_cpu, sync, idx,
load, this_load, imbalance)) load, this_load, imbalance))
return this_cpu; return this_cpu;
if (prev_cpu == this_cpu)
goto out;
/* /*
* Start passive balancing when half the imbalance_pct * Start passive balancing when half the imbalance_pct
* limit is reached. * limit is reached.