Commit-ID: 71a29aa7b600595d0ef373ea605ac656876d1f2f Gitweb: http://git.kernel.org/tip/71a29aa7b600595d0ef373ea605ac656876d1f2f Author: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> AuthorDate: Mon, 7 Sep 2009 18:28:05 +0200 Committer: Ingo Molnar <mingo@xxxxxxx> CommitDate: Mon, 7 Sep 2009 20:39:06 +0200 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@xxxxxxxxx> LKML-Reference: <new-submission> Signed-off-by: Ingo Molnar <mingo@xxxxxxx> --- 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 d7fda41..cc97ea4 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)); /* -- To unsubscribe from this list: send the line "unsubscribe linux-tip-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|