Messages in this thread | | | Subject | Re: [PATCH 3/8] sched: don't consider other cpus in our group in case of NEWLY_IDLE | From | Peter Zijlstra <> | Date | Tue, 19 Mar 2013 15:20:57 +0100 |
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On Thu, 2013-02-14 at 14:48 +0900, Joonsoo Kim wrote: > Commit 88b8dac0 makes load_balance() consider other cpus in its group, > regardless of idle type. When we do NEWLY_IDLE balancing, we should not > consider it, because a motivation of NEWLY_IDLE balancing is to turn > this cpu to non idle state if needed. This is not the case of other cpus. > So, change code not to consider other cpus for NEWLY_IDLE balancing. > > With this patch, assign 'if (pulled_task) this_rq->idle_stamp = 0' > in idle_balance() is corrected, because NEWLY_IDLE balancing doesn't > consider other cpus. Assigning to 'this_rq->idle_stamp' is now valid. > > Cc: Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Fair enough, good catch.
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 0c6aaf6..97498f4 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5016,8 +5016,15 @@ static int load_balance(int this_cpu, struct rq *this_rq, > .cpus = cpus, > }; > > + /* For NEWLY_IDLE load_balancing, we don't need to consider > + * other cpus in our group */ > + if (idle == CPU_NEWLY_IDLE) { > + env.dst_grpmask = NULL; > + max_lb_iterations = 0;
Just a small nit; I don't think we'll ever get to evaluate max_lb_iterations when !dst_grpmask. So strictly speaking its superfluous to touch it.
> + } else { > + max_lb_iterations = cpumask_weight(env.dst_grpmask); > + } > cpumask_copy(cpus, cpu_active_mask); > - max_lb_iterations = cpumask_weight(env.dst_grpmask); > > schedstat_inc(sd, lb_count[idle]); >
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