lkml.org 
[lkml]   [2018]   [Dec]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRe: [PATCH 2/3] sched/fair: trigger asym_packing during idle load balance
    On Thu, 20 Dec 2018 at 12:19, Valentin Schneider
    <valentin.schneider@arm.com> wrote:
    >
    > On 20/12/2018 07:55, Vincent Guittot wrote:
    > > newly idle load balance is not always triggered when a cpu becomes idle.
    > > This prevent the scheduler to get a chance to migrate task for asym packing.
    > > Enable active migration because of asym packing during idle load balance too.
    > >
    > > Signed-off-by: Vincent Guittot <vincent.guittot@linaro.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 9b31247..487c73e 100644
    > > --- a/kernel/sched/fair.c
    > > +++ b/kernel/sched/fair.c
    > > @@ -8853,7 +8853,7 @@ static int need_active_balance(struct lb_env *env)
    > > {
    > > struct sched_domain *sd = env->sd;
    > >
    > > - if (env->idle == CPU_NEWLY_IDLE) {
    > > + if (env->idle != CPU_NOT_IDLE) {
    > >
    > > /*
    > > * ASYM_PACKING needs to force migrate tasks from busy but
    > >
    >
    > Regarding just extending the condition to include idle balance:
    >
    > Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
    >
    >
    > As in the previous thread, I'll still argue that if you want to *reliably*
    > exploit newidle balances to do asym packing active balancing, you should
    > add some logic to raise rq->rd->overload when we notice some asym packing
    > could be done, so that it can be leveraged by a higher-priority CPU doing
    > a newidle balance.

    The source cpu with the task is never overloaded.
    We need to start the load balance to know that it's worth migrating the task.

    >
    > Otherwise the few newidle asym-packing active balances you'll get will be
    > due to somewhat random luck because we happened to set that overload flag
    > at some point.

    \
     
     \ /
      Last update: 2018-12-20 15:34    [W:4.781 / U:0.000 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site