linux-kernel - Re: [tip:sched/core] sched/fair: Fix rounding bug for asym packing

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Message-ID: <CAKfTPtCJz2YDRirQ1JhrvtZMju-CkwzzxLk7JfMeGvVMKeScXA@mail.gmail.com>
Date:   Mon, 21 Jan 2019 14:22:17 +0100
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-tip-commits@...r.kernel.org,
        Valentin Schneider <valentin.schneider@....com>
Subject: Re: [tip:sched/core] sched/fair: Fix rounding bug for asym packing

On Mon, 21 Jan 2019 at 13:47, Peter Zijlstra <peterz@...radead.org> wrote:
>
>
> Sorry guys, I seem to have messed this up :/
>
> Valentin pointed me out that I missed v3 and v4 of these patches; v3 got

I was about to sent an email about that too

> lost in the x-mas pile and v4 was actually on my todo list for this
> week, but I'd forgotten I'd already queued v2.
>
> I'll go queue delta patches.

Thanks

>
> On Mon, Jan 21, 2019 at 03:33:53AM -0800, tip-bot for Vincent Guittot wrote:
> > index 50aa2aba69bd..2ccd6e093326 100644
> > --- a/kernel/sched/fair.c
> > +++ b/kernel/sched/fair.c
> > @@ -8190,6 +8190,12 @@ static inline void update_sg_lb_stats(struct lb_env *env,
> >       /* Adjust by relative CPU capacity of the group */
> >       sgs->group_capacity = group->sgc->capacity;
> >       sgs->avg_load = (sgs->group_load*SCHED_CAPACITY_SCALE) / sgs->group_capacity;
> > +     /*
> > +      * Prevent division rounding to make the computation of imbalance
> > +      * slightly less than original value and to prevent the rq to be then
> > +      * selected as busiest queue:
> > +      */
> > +     sgs->avg_load += 1;
> >
> >       if (sgs->sum_nr_running)
> >               sgs->load_per_task = sgs->sum_weighted_load / sgs->sum_nr_running;
>
>