Messages in this thread Patch in this message | | | Date | Wed, 6 Nov 2013 05:20:09 -0800 | From | tip-bot for Vaidyanathan Srinivasan <> | Subject | [tip:sched/core] sched: Fix asymmetric scheduling for POWER7 |
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Commit-ID: 2042abe7977222ef606306faa2dce8fd51e98e65 Gitweb: http://git.kernel.org/tip/2042abe7977222ef606306faa2dce8fd51e98e65 Author: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> AuthorDate: Wed, 30 Oct 2013 08:42:42 +0530 Committer: Ingo Molnar <mingo@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.neuling@au1.ibm.com> Signed-off-by: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com> Signed-off-by: Preeti U Murthy <preeti@linux.vnet.ibm.com> Tested-by: Michael Neuling <mikey@neuling.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Cc: vincent.guittot@linaro.org Cc: bitbucket@online.de Cc: benh@kernel.crashing.org Cc: anton@samba.org Cc: Morten.Rasmussen@arm.com Cc: pjt@google.com Link: http://lkml.kernel.org/r/20131030031242.23426.13019.stgit@preeti.in.ibm.com Signed-off-by: Ingo Molnar <mingo@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;
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