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    SubjectRe: [PATCH v5 2/2] sched: make update_cpu_load_nohz() consider missed ticks in NOHZ_FULL
    On Fri, Nov 20, 2015 at 02:19:55PM +0100, Peter Zijlstra wrote:
    > On Tue, Nov 10, 2015 at 09:36:02AM +0900, byungchul.park@lge.com wrote:
    > > +++ b/kernel/sched/fair.c
    > > @@ -4419,10 +4419,11 @@ static void update_idle_cpu_load(struct rq *this_rq)
    > > /*
    > > * Called from tick_nohz_idle_exit() -- try and fix up the ticks we missed.
    > > */
    > > -void update_cpu_load_nohz(void)
    > > +void update_cpu_load_nohz(int active)
    > > {
    > > struct rq *this_rq = this_rq();
    > > unsigned long curr_jiffies = READ_ONCE(jiffies);
    > > + unsigned long load = active ? weighted_cpuload(cpu_of(this_rq)) : 0;
    > > unsigned long pending_updates;
    > >
    > > if (curr_jiffies == this_rq->last_load_update_tick)
    > > @@ -4433,10 +4434,11 @@ void update_cpu_load_nohz(void)
    > > if (pending_updates) {
    > > this_rq->last_load_update_tick = curr_jiffies;
    > > /*
    > > - * We were idle, this means load 0, the current load might be
    > > - * !0 due to remote wakeups and the sort.
    > > + * In the regular NOHZ case, we were idle, this means load 0.
    > > + * In the NOHZ_FULL case, we were non-idle, we should consider
    > > + * its weighted load.
    > > */
    > > - __update_cpu_load(this_rq, 0, pending_updates, 0);
    > > + __update_cpu_load(this_rq, load, pending_updates, active);
    > > }
    > > raw_spin_unlock(&this_rq->lock);
    > > }
    >
    > Bah, so I did all the work to get the actual number of lost ticks in
    > there, only to _then_ find out that's mostly pointless :-)
    >
    > The problem is update_idle_cpu_load() is called while idle (from another
    > CPU), so it still needs the whole jiffy based thing.
    >
    > So I'll take this patch for now. Thanks.

    Thank you.

    Byungchul

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