[tip:sched/core] sched: Fix asymmetric scheduling for POWER7
Commit-ID: 2042abe7977222ef606306faa2dce8fd51e98e65 Gitweb: http://git.kernel.org/tip/2042abe7977222ef606306faa2dce8fd51e98e65 Author: Vaidyanathan Srinivasan AuthorDate: Wed, 30 Oct 2013 08:42:42 +0530 Committer: Ingo Molnar 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 Signed-off-by: Vaidyanathan Srinivasan Signed-off-by: Preeti U Murthy Tested-by: Michael Neuling Signed-off-by: Peter Zijlstra Cc: vincent.guit...@linaro.org Cc: bitbuc...@online.de Cc: b...@kernel.crashing.org Cc: an...@samba.org Cc: morten.rasmus...@arm.com Cc: p...@google.com Link: http://lkml.kernel.org/r/20131030031242.23426.13019.st...@preeti.in.ibm.com Signed-off-by: Ingo Molnar --- 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-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[tip:sched/core] sched: Fix asymmetric scheduling for POWER7
Commit-ID: 2042abe7977222ef606306faa2dce8fd51e98e65 Gitweb: http://git.kernel.org/tip/2042abe7977222ef606306faa2dce8fd51e98e65 Author: Vaidyanathan Srinivasan sva...@linux.vnet.ibm.com AuthorDate: Wed, 30 Oct 2013 08:42:42 +0530 Committer: Ingo Molnar mi...@kernel.org 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.neul...@au1.ibm.com Signed-off-by: Vaidyanathan Srinivasan sva...@linux.vnet.ibm.com Signed-off-by: Preeti U Murthy pre...@linux.vnet.ibm.com Tested-by: Michael Neuling mi...@neuling.org Signed-off-by: Peter Zijlstra pet...@infradead.org Cc: vincent.guit...@linaro.org Cc: bitbuc...@online.de Cc: b...@kernel.crashing.org Cc: an...@samba.org Cc: morten.rasmus...@arm.com Cc: p...@google.com Link: http://lkml.kernel.org/r/20131030031242.23426.13019.st...@preeti.in.ibm.com Signed-off-by: Ingo Molnar mi...@kernel.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 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-kernel in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
