Commit-ID: 2042abe7977222ef606306faa2dce8fd51e98e65 Gitweb: http://git.kernel.org/tip/2042abe7977222ef606306faa2dce8fd51e98e65 Author: Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx> AuthorDate: Wed, 30 Oct 2013 08:42:42 +0530 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitDate: Wed, 6 Nov 2013 12:37:54 +0100 sched: Fix asymmetric scheduling for POWER7 Asymmetric scheduling within a core is a scheduler loadbalancing feature that is triggered when SD_ASYM_PACKING flag is set. The goal for the load balancer is to move tasks to lower order idle SMT threads within a core on a POWER7 system. In nohz_kick_needed(), we intend to check if our sched domain (core) is completely busy or we have idle cpu. The following check for SD_ASYM_PACKING: (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu) already covers the case of checking if the domain has an idle cpu, because cpumask_first_and() will not yield any set bits if this domain has no idle cpu. Hence, nr_busy check against group weight can be removed. Reported-by: Michael Neuling <michael.neuling@xxxxxxxxxxx> Signed-off-by: Vaidyanathan Srinivasan <svaidy@xxxxxxxxxxxxxxxxxx> Signed-off-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx> Tested-by: Michael Neuling <mikey@xxxxxxxxxxx> Signed-off-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: vincent.guittot@xxxxxxxxxx Cc: bitbucket@xxxxxxxxx Cc: benh@xxxxxxxxxxxxxxxxxxx Cc: anton@xxxxxxxxx Cc: Morten.Rasmussen@xxxxxxx Cc: pjt@xxxxxxxxxx Link: http://lkml.kernel.org/r/20131030031242.23426.13019.stgit@xxxxxxxxxxxxxxxxx Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> --- kernel/sched/fair.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 41c02b6..074551a 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6800,7 +6800,7 @@ static inline int nohz_kick_needed(struct rq *rq, int cpu) if (sd->flags & SD_SHARE_PKG_RESOURCES && nr_busy > 1) goto need_kick_unlock; - if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight + if (sd->flags & SD_ASYM_PACKING && (cpumask_first_and(nohz.idle_cpus_mask, sched_domain_span(sd)) < cpu)) goto need_kick_unlock; -- 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