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From: Brendan Jackman <brendan.jackman@arm.com>
To: Joel Fernandes <joelaf@google.com>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
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Subject: Re: [PATCH RFC 5/5] sched/fair: remove impossible condition from find_idlest_group_cpu
In-reply-to: <20171028095941.4773-6-joelaf@google.com>
Date: Mon, 30 Oct 2017 15:41:58 +0000
Message-ID: <87tvygk5h5.fsf@arm.com>
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On Sat, Oct 28 2017 at 09:59, Joel Fernandes wrote:
> find_idlest_group_cpu goes through CPUs of a group previous selected by
> find_idlest_group. find_idlest_group returns NULL if the local group is the
> selected one and doesn't execute find_idlest_group_cpu if the group to which
> 'cpu' belongs to is chosen. So we're always guaranteed to call
> find_idlest_group_cpu with a group to which cpu is non-local. This makes one of
> the conditions in find_idlest_group_cpu an impossible one, which we can get rid
> off.
>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Brendan Jackman <brendan.jackman@arm.com>
> Cc: Dietmar <dietmar.eggemann@arm.com>
> Signed-off-by: Joel Fernandes <joelaf@google.com>

FWIW:

Reviewed-by: Brendan Jackman <brendan.jackman@arm.com>

> ---
>  kernel/sched/fair.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 5c49fdb4c508..740602ce799f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -5922,7 +5922,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this
>  			}
>  		} else if (shallowest_idle_cpu == -1) {
>  			load = weighted_cpuload(cpu_rq(i));
> -			if (load < min_load || (load == min_load && i == this_cpu)) {
> +			if (load < min_load) {
>  				min_load = load;
>  				least_loaded_cpu = i;
>  			}