sched: fix sleeper bonus limit

There is an Amarok song switch time increase (regression) under
hefty load.

What is happening is that sleeper_bonus is never consumed, and only
rarely goes below runtime_limit, so for the most part, Amarok isn't
getting any bonus at all.  We're keeping sleeper_bonus right at
runtime_limit (sched_latency == sched_runtime_limit == 40ms) forever, ie
we don't consume if we're lower that that, and don't add if we're above
it.  One Amarok thread waking (or anybody else) will push us past the
threshold, so the next thread waking gets nada, but will reap pain from
the previous thread waking until we drop back to runtime_limit.  It
looks to me like under load, some random task gets a bonus, and
everybody else pays, whether deserving or not.

This diff fixed the regression for me at any load rate.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>

1 files changed, 1 insertions, 1 deletions

diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c
index ee3771850aaf..9f53d49f3aab 100644
--- a/kernel/sched_fair.c
+++ b/kernel/sched_fair.c
@@ -354,7 +354,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr)
         delta_fair = calc_delta_fair(delta_exec, lw);
         delta_mine = calc_delta_mine(delta_exec, curr->load.weight, lw);
 
-        if (cfs_rq->sleeper_bonus > sysctl_sched_latency) {
+        if (cfs_rq->sleeper_bonus > sysctl_sched_min_granularity) {
                 delta = min((u64)delta_mine, cfs_rq->sleeper_bonus);
                 delta = min(delta, (unsigned long)(
                         (long)sysctl_sched_runtime_limit - curr->wait_runtime));