Commit 64b9e029 authored by Amit K. Arora's avatar Amit K. Arora Committed by Ingo Molnar
Browse files

sched: minor optimizations in wake_affine and select_task_rq_fair 



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: default avatarAmit K Arora <aarora@linux.vnet.ibm.com>
Acked-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent b87f1724

kernel/sched_fair.c

+7 −9
Original line number Diff line number Diff line
@@ -1088,7 +1088,7 @@ static inline unsigned long effective_load(struct task_group *tg, int cpu, 
#endif



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,

	    int idx, unsigned long load, unsigned long this_load,

	    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);

	tl_per_task = cpu_avg_load_per_task(this_cpu);



	if ((tl <= load && tl + target_load(prev_cpu, idx) <= tl_per_task) ||

			balanced) {

	if (balanced || (tl <= load && tl + target_load(prev_cpu, idx) <=

			tl_per_task)) {

		/*

		 * This domain has SD_WAKE_AFFINE 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;

	int prev_cpu, this_cpu, new_cpu;

	unsigned long load, this_load;

	struct rq *rq, *this_rq;

	struct rq *this_rq;

	unsigned int imbalance;

	int idx;



	prev_cpu	= task_cpu(p);

	rq		= task_rq(p);

	this_cpu	= smp_processor_id();

	this_rq		= cpu_rq(this_cpu);

	new_cpu		= prev_cpu;



	if (prev_cpu == this_cpu)

		goto out;

	/*

	 * 'this_sd' is the first domain that both

	 * 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);

	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))

		return this_cpu;



	if (prev_cpu == this_cpu)

		goto out;



	/*

	 * Start passive balancing when half the imbalance_pct

	 * limit is reached.

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