Commit 4be9daaa authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: fix task_h_load() 



Currently task_h_load() computes the load of a task and uses that to either
subtract it from the total, or add to it.

However, removing or adding a task need not have any effect on the total load
at all. Imagine adding a task to a group that is local to one cpu - in that
case the total load of that cpu is unaffected.

So properly compute addition/removal:

 s_i = S * rw_i / \Sum_j rw_j
 s'_i = S * (rw_i + wl) / (\Sum_j rw_j + wg)

then s'_i - s_i gives the change in load.

Where s_i is the shares for cpu i, S the group weight, rw_i the runqueue weight
for that cpu, wl the weight we add (subtract) and wg the weight contribution to
the runqueue.

Signed-off-by: default avatarPeter Zijlstra <peterz@infradead.org>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 42a3ac7d

kernel/sched_fair.c

+40 −9
Original line number Diff line number Diff line
@@ -1074,22 +1074,53 @@ static inline int wake_idle(int cpu, struct task_struct *p) 
static const struct sched_class fair_sched_class;



#ifdef CONFIG_FAIR_GROUP_SCHED

static unsigned long task_h_load(struct task_struct *p)

static unsigned long effective_load(struct task_group *tg, long wl, int cpu)

{

	unsigned long h_load = p->se.load.weight;

	struct cfs_rq *cfs_rq = cfs_rq_of(&p->se);

	struct sched_entity *se = tg->se[cpu];

	long wg = wl;



	update_h_load(task_cpu(p));

	for_each_sched_entity(se) {

#define D(n) (likely(n) ? (n) : 1)



		long S, Srw, rw, s, sn;



		S = se->my_q->tg->shares;

		s = se->my_q->shares;

		rw = se->my_q->load.weight;



	h_load = calc_delta_mine(h_load, cfs_rq->h_load, &cfs_rq->load);

		Srw = S * rw / D(s);

		sn = S * (rw + wl) / D(Srw + wg);



		wl = sn - s;

		wg = 0;

#undef D

	}



	return h_load;

	return wl;

}



static unsigned long task_load_sub(struct task_struct *p)

{

	return effective_load(task_group(p), -(long)p->se.load.weight, task_cpu(p));

}



static unsigned long task_load_add(struct task_struct *p, int cpu)

{

	return effective_load(task_group(p), p->se.load.weight, cpu);

}



#else

static unsigned long task_h_load(struct task_struct *p)



static unsigned long task_load_sub(struct task_struct *p)

{

	return -p->se.load.weight;

}



static unsigned long task_load_add(struct task_struct *p, int cpu)

{

	return p->se.load.weight;

}



#endif



static int
@@ -1112,9 +1143,9 @@ wake_affine(struct rq *rq, struct sched_domain *this_sd, struct rq *this_rq, 
	 * of the current CPU:

	 */

	if (sync)

		tl -= task_h_load(current);

		tl += task_load_sub(current);



	balanced = 100*(tl + task_h_load(p)) <= imbalance*load;

	balanced = 100*(tl + task_load_add(p, this_cpu)) <= imbalance*load;



	/*

	 * If the currently running task will sleep within

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