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sched: tidy up and simplify the bonus balance 

make the bonus balance more consistent: do not hand out a bonus if
there's too much in flight already, and only deduct as much from a
runner as it has the capacity. This makes the bonus engine a zero-sum
game (as intended).

this also simplifies the code:

   text    data     bss     dec     hex filename
  34770    2998      24   37792    93a0 sched.o.before
  34749    2998      24   37771    938b sched.o.after

and it also avoids overscheduling in sleep-happy workloads like
hackbench.c.

Signed-off-by: Ingo Molnar <mingo@elte.hu>
This commit is contained in:
Ingo Molnar 2007-08-24 20:39:10 +02:00
parent 98fbc79853
commit b2133c8b1e
1 changed files with 10 additions and 4 deletions
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14
kernel/sched_fair.c
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@ -306,6 +306,8 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr)
delta = min(cfs_rq->sleeper_bonus, (u64)delta_exec);
delta = calc_delta_mine(delta, curr->load.weight, lw);
delta = min((u64)delta, cfs_rq->sleeper_bonus);
delta = min(delta, (unsigned long)(
(long)sysctl_sched_runtime_limit - curr->wait_runtime));
cfs_rq->sleeper_bonus -= delta;
delta_mine -= delta;
}
@ -493,6 +495,13 @@ static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
unsigned long load = cfs_rq->load.weight, delta_fair;
long prev_runtime;
/*
* Do not boost sleepers if there's too much bonus 'in flight'
* already:
*/
if (unlikely(cfs_rq->sleeper_bonus > sysctl_sched_runtime_limit))
return;
if (sysctl_sched_features & SCHED_FEAT_SLEEPER_LOAD_AVG)
load = rq_of(cfs_rq)->cpu_load[2];
@ -512,16 +521,13 @@ static void __enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)
prev_runtime = se->wait_runtime;
__add_wait_runtime(cfs_rq, se, delta_fair);
schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
delta_fair = se->wait_runtime - prev_runtime;
/*
* Track the amount of bonus we've given to sleepers:
*/
cfs_rq->sleeper_bonus += delta_fair;
if (unlikely(cfs_rq->sleeper_bonus > sysctl_sched_runtime_limit))
cfs_rq->sleeper_bonus = sysctl_sched_runtime_limit;
schedstat_add(cfs_rq, wait_runtime, se->wait_runtime);
}
static void enqueue_sleeper(struct cfs_rq *cfs_rq, struct sched_entity *se)