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Date: Wed, 30 Oct 2013 08:42:42 +0530 From: Preeti U Murthy <preeti@...ux.vnet.ibm.com> To: peterz@...radead.org, mikey@...ling.org, svaidy@...ux.vnet.ibm.com, mingo@...nel.org Cc: vincent.guittot@...aro.org, bitbucket@...ine.de, benh@...nel.crashing.org, linux-kernel@...r.kernel.org, anton@...ba.org, linuxppc-dev@...ts.ozlabs.org, Morten.Rasmussen@....com, pjt@...gle.com Subject: [PATCH V2 1/2] sched: Fix asymmetric scheduling for POWER7 From: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com> 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@....ibm.com> Signed-off-by: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com> Signed-off-by: Preeti U Murthy <preeti@...ux.vnet.ibm.com> Tested-by: Michael Neuling <mikey@...ling.org> --- 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 813dd61..e9c9549 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -6781,7 +6781,7 @@ 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-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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