linux-kernel - Re: [PATCH 06/16] sched: Disable WAKE_AFFINE for asymmetric configurations

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Message-ID: <CAKfTPtBLfm5BSd-r+qcdyThixdG282kgQvPVWuVDkV3xKJMiMA@mail.gmail.com>
Date:	Tue, 24 May 2016 11:10:28 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Morten Rasmussen <morten.rasmussen@....com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Yuyang Du <yuyang.du@...el.com>, mgalbraith@...e.de,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 06/16] sched: Disable WAKE_AFFINE for asymmetric configurations

On 23 May 2016 at 12:58, Morten Rasmussen <morten.rasmussen@....com> wrote:
> If the system has cpu of different compute capacities (e.g. big.LITTLE)
> let affine wakeups be constrained to cpus of the same type.

Can you explain why you don't want wake affine with cpus with
different compute capacity ?

>
> cc: Ingo Molnar <mingo@...hat.com>
> cc: Peter Zijlstra <peterz@...radead.org>
>
> Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
> ---
>  kernel/sched/core.c | 3 +++
>  1 file changed, 3 insertions(+)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index d9619a3..558ec4a 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6410,6 +6410,9 @@ sd_init(struct sched_domain_topology_level *tl, int cpu)
>                 sd->idle_idx = 1;
>         }
>
> +       if (sd->flags & SD_ASYM_CPUCAPACITY)
> +               sd->flags &= ~SD_WAKE_AFFINE;
> +
>         sd->private = &tl->data;
>
>         return sd;
> --
> 1.9.1
>