Messages in this thread | | | From | Brendan Jackman <> | Subject | Re: [PATCH v2] sched/fair: Sync task util before slow-path wakeup | Date | Wed, 20 Sep 2017 18:17:04 +0100 |
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Hi Peter,
Ping.
Log of previous discussion: https://patchwork.kernel.org/patch/9876769/
Cheers, Brendan
On Tue, Aug 08 2017 at 09:55, Brendan Jackman wrote: > We use task_util in find_idlest_group via capacity_spare_wake. This > task_util is updated in wake_cap. However wake_cap is not the only > reason for ending up in find_idlest_group - we could have been sent > there by wake_wide. So explicitly sync the task util with prev_cpu > when we are about to head to find_idlest_group. > > We could simply do this at the beginning of > select_task_rq_fair (i.e. irrespective of whether we're heading to > select_idle_sibling or find_idlest_group & co), but I didn't want to > slow down the select_idle_sibling path more than necessary. > > Don't do this during fork balancing, we won't need the task_util and > we'd just clobber the last_update_time, which is supposed to be 0. > > Signed-off-by: Brendan Jackman <brendan.jackman@arm.com> > Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> > Cc: Vincent Guittot <vincent.guittot@linaro.org> > Cc: Josef Bacik <josef@toxicpanda.com> > Cc: Ingo Molnar <mingo@redhat.com> > Cc: Morten Rasmussen <morten.rasmussen@arm.com> > Cc: Peter Zijlstra <peterz@infradead.org> > --- > > changes v1 -> v2: Just cosmetic > > kernel/sched/fair.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c95880e216f6..20275178604d 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -5913,8 +5913,17 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f > new_cpu = cpu; > } > > + if (sd && !(sd_flag & SD_BALANCE_FORK)) { > + /* > + * We're going to need the task's util for capacity_spare_wake > + * in find_idlest_group. Sync it up to prev_cpu's > + * last_update_time. > + */ > + sync_entity_load_avg(&p->se); > + } > + > if (!sd) { > - pick_cpu: > +pick_cpu: > if (sd_flag & SD_BALANCE_WAKE) /* XXX always ? */ > new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);
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