On 19 Aug 2015 17:58, "Jon Medhurst (Tixy)" <tixy@linaro.org> wrote:
>
> Adding Patrick Bellasi to the 'to' list as he's been working on HMP with
> Chris Redpath....
>
>
> On Wed, 2015-08-19 at 05:18 +0000, Rahul Khandelwal (Rahul Khandelwal) wrote:
>
> Dear All,
>
> Please consider the  patch, It is related to HMP force up migration. It will avoid sending of unnecessary interrupts to CPUs of faster domain hence increase performance.
>
> --------------------------------------------------------------------------------------------------
> From 2d48749ac30a2c0a2ef77132f303d69605c3dd3f Mon Sep 17 00:00:00 2001
> From: rahulkhandelwal <rahul.khandelwal@spreadtrum.com>
> Date: Fri, 14 Aug 2015 16:36:17 +0800
> Subject: [PATCH 1/1] HMP: Do not send IPI if core already waked up
>
> It is possible that we are sending IPI to a cpu in faster domain which is
> already waked up by other CPU in smaller domain.
>
> HMP select the idle CPU using hmp_domain_min_load. Based on that HMP send IPI
> to the idle cpu in faster domain. There could be some latency by the core to
> wake up and set wake_for_idle_pull = 0. Next smaller cpu again check for
> idle CPU in faster domain and send IPI to already waked up CPU.
>
> For example: In Octacore system, 0-3 are slower CPUs and 4-7 are faster CPUs.
> CPU0 and CPU1 has heavy tasks and CPU4 is idle.
> CPU0 execute hmp_force_up_migration find CPU4 as idle, it send IPI to CPU4
> and return. After that CPU1 got the chance to run hmp_force_up_migration,
> it again find CPU4 as idle, send IPI to CPU4, which is not required.
>
> Signed-off-by: rahulkhandelwal <rahul.khandelwal@spreadtrum.com>
> ---
> kernel/sched/fair.c |    5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 1baf641..388836c 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7200,6 +7200,11 @@ static void hmp_force_up_migration(int this_cpu)
>                                }
>                                p = task_of(curr);
>                                if (hmp_up_migration(cpu, &target_cpu, curr)) {
> +                                             if (cpu_rq(target_cpu)->wake_for_idle_pull == 1) {
> +                                                             raw_spin_unlock_irqrestore(&target->lock, flags);
> +                                                             spin_unlock(&hmp_force_migration);
> +                                                             return;
> +                                             }
>                                                cpu_rq(target_cpu)->wake_for_idle_pull = 1;
>                                                raw_spin_unlock_irqrestore(&target->lock, flags);
>                                                spin_unlock(&hmp_force_migration);

Can you please share the actual performance numbers gained by this patch?

> --
> 1.7.9.5
>
>
>
>
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