[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20180705133142.GD32579@e108498-lin.cambridge.arm.com>
Date: Thu, 5 Jul 2018 14:31:43 +0100
From: Quentin Perret <quentin.perret@....com>
To: Morten Rasmussen <morten.rasmussen@....com>
Cc: peterz@...radead.org, mingo@...hat.com, valentin.schneider@....com,
dietmar.eggemann@....com, vincent.guittot@...aro.org,
gaku.inami.xh@...esas.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv4 11/12] sched/core: Disable SD_ASYM_CPUCAPACITY for
root_domains without asymmetry
Hi Morten,
On Wednesday 04 Jul 2018 at 11:17:49 (+0100), Morten Rasmussen wrote:
> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
> index 71330e0e41db..29c186961345 100644
> --- a/kernel/sched/topology.c
> +++ b/kernel/sched/topology.c
> @@ -1160,6 +1160,26 @@ sd_init(struct sched_domain_topology_level *tl,
> sd_id = cpumask_first(sched_domain_span(sd));
>
> /*
> + * Check if cpu_map eclipses cpu capacity asymmetry.
> + */
> +
> + if (sd->flags & SD_ASYM_CPUCAPACITY) {
> + int i;
> + bool disable = true;
> + long capacity = arch_scale_cpu_capacity(NULL, sd_id);
> +
> + for_each_cpu(i, sched_domain_span(sd)) {
> + if (capacity != arch_scale_cpu_capacity(NULL, i)) {
> + disable = false;
> + break;
> + }
> + }
> +
> + if (disable)
> + sd->flags &= ~SD_ASYM_CPUCAPACITY;
> + }
> +
> + /*
> * Convert topological properties into behaviour.
> */
If SD_ASYM_CPUCAPACITY means that some CPUs have different
arch_scale_cpu_capacity() values, we could also automatically _set_
the flag in sd_init() no ? Why should we let the arch set it and just
correct it later ?
I understand the moment at which we know the capacities of CPUs varies
from arch to arch, but the arch code could just call
rebuild_sched_domain when the capacities of CPUs change and let the
scheduler detect things automatically. I mean, even if the arch code
sets the flag in its topology level table, it will have to rebuild
the sched domains anyway ...
What do you think ?
Thanks,
Quentin
Powered by blists - more mailing lists