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sched: fix task_h_load()

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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: Peter Zijlstra <peterz@infradead.org>
Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Peter Zijlstra 2008-06-27 13:41:30 +02:00 committed by Ingo Molnar
parent 42a3ac7d5c
commit 4be9daaa1b
1 changed files with 40 additions and 9 deletions
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49
kernel/sched_fair.c
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@ -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)
h_load = calc_delta_mine(h_load, cfs_rq->h_load, &cfs_rq->load);
long S, Srw, rw, s, sn;
return h_load;
S = se->my_q->tg->shares;
s = se->my_q->shares;
rw = se->my_q->load.weight;
Srw = S * rw / D(s);
sn = S * (rw + wl) / D(Srw + wg);
wl = sn - s;
wg = 0;
#undef D
}
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