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| author | Peter Zijlstra <a.p.zijlstra@chello.nl> | 2009-09-07 18:28:05 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@elte.hu> | 2009-09-07 20:39:06 +0200 |
| commit | 71a29aa7b600595d0ef373ea605ac656876d1f2f (patch) | |
| tree | 1288e5bd2bd4b5c599c2b8c7649c30987101a8ec /kernel/sched_fair.c | |
| parent | cdd2ab3de4301728b20efd6225681d3ff591a938 (diff) | |
| download | lwn-71a29aa7b600595d0ef373ea605ac656876d1f2f.tar.gz lwn-71a29aa7b600595d0ef373ea605ac656876d1f2f.zip | |
sched: Deal with low-load in wake_affine()
wake_affine() would always fail under low-load situations where
both prev and this were idle, because adding a single task will
always be a significant imbalance, even if there's nothing
around that could balance it.
Deal with this by allowing imbalance when there's nothing you
can do about it.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/sched_fair.c')
| -rw-r--r-- | kernel/sched_fair.c | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/kernel/sched_fair.c b/kernel/sched_fair.c index d7fda41ddaf0..cc97ea498f24 100644 --- a/kernel/sched_fair.c +++ b/kernel/sched_fair.c @@ -1262,7 +1262,17 @@ wake_affine(struct sched_domain *this_sd, struct rq *this_rq, tg = task_group(p); weight = p->se.load.weight; - balanced = 100*(tl + effective_load(tg, this_cpu, weight, weight)) <= + /* + * In low-load situations, where prev_cpu is idle and this_cpu is idle + * due to the sync cause above having dropped tl to 0, we'll always have + * an imbalance, but there's really nothing you can do about that, so + * that's good too. + * + * Otherwise check if either cpus are near enough in load to allow this + * task to be woken on this_cpu. + */ + balanced = !tl || + 100*(tl + effective_load(tg, this_cpu, weight, weight)) <= imbalance*(load + effective_load(tg, prev_cpu, 0, weight)); /* |