Vaidyanathan Srinivasan <sva...@linux.vnet.ibm.com> wrote: > 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>
Tested-by: Michael Neuling <mi...@neuling.org> Peter, I tested this only a brief while back but it turned out my test wasn't stringent enough and it was actually broken (in v3.9). This fixes it. Mikey > Signed-off-by: Vaidyanathan Srinivasan <sva...@linux.vnet.ibm.com> > Signed-off-by: Preeti U Murthy <pre...@linux.vnet.ibm.com> > --- > kernel/sched/fair.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 12f0eab..828ed97 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5821,8 +5821,8 @@ static inline int nohz_kick_needed(struct rq *rq, int > cpu) > goto need_kick_unlock; > } > > - if (sd->flags & SD_ASYM_PACKING && nr_busy != sg->group_weight > - && (cpumask_first_and(nohz.idle_cpus_mask, > + if (sd->flags & SD_ASYM_PACKING && > + (cpumask_first_and(nohz.idle_cpus_mask, > sched_domain_span(sd)) < cpu)) > goto need_kick_unlock; > > _______________________________________________ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
