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authorVaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>2013-10-30 08:42:42 +0530
committerIngo Molnar <mingo@kernel.org>2013-11-06 12:37:54 +0100
commit2042abe7977222ef606306faa2dce8fd51e98e65 (patch)
tree5f4c647b97c6dae097fd8b6e05cf34c4fb3db7fd /kernel/sched
parentb8a216269ec0ce2e961d32e6d640d7010b8a818e (diff)
downloadblackbird-op-linux-2042abe7977222ef606306faa2dce8fd51e98e65.tar.gz
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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>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/fair.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 41c02b6b090e..074551a792f7 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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