linux-kernel - Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY

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Message-ID: <CA+KHdyVitkZvSpr_OvzpeZ4BFQ1Y5RiLj-EtkSWTRHu56dKzzw@mail.gmail.com>
Date:   Thu, 16 Feb 2017 12:20:39 +0100
From:   Uladzislau Rezki <urezki@...il.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Uladzislau 2 Rezki <uladzislau2.rezki@...ymobile.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: Re: [RFC,v2 3/3] sched: ignore task_h_load for CPU_NEWLY_IDLE

On Wed, Feb 15, 2017 at 7:58 PM, Dietmar Eggemann
<dietmar.eggemann@....com> wrote:
> On 02/14/2017 06:28 PM, Uladzislau Rezki wrote:
>>>>
>>>>
>>>> So that is useful information that should have been in the Changelog.
>>>>
>>>> OK, can you respin this patch with adjusted Changelog and taking Mike's
>>>> feedback?
>>>>
>>> Yes, i will prepare a patch accordingly, no problem.
>>>
>>>>
>>>> Also, I worry about the effects of this on !PREEMPT kernels, the first
>>>> hunk (which explicitly states is about latency) should be under
>>>> CONFIG_PREEMPT to match the similar case we already have in
>>>> detach_tasks().
>
>
> This one uses #ifdef CONFIG_PREEMPT whereas you use
> IS_ENABLED(CONFIG_PREEMPT). Is there a particular reason for this?
>
I just wanted to put it under one line instead of using #ifdefs in my
second hunk,
so that is a matter of taste. Also, please find below different
variants of how it can be
rewriten:

<variant 1>
#ifdef CONFIG_PREEMPT
    if (env->idle != CPU_NEWLY_IDLE)
#endif
        if ((load / 2) > env->imbalance)
            goto next;
<variant 1>

<variant 2>
#ifdef CONFIG_PREEMPT
    if (env->idle != CPU_NEWLY_IDLE &&
            (load / 2) > env->imbalance)
        goto next;
#else
    if ((load / 2) > env->imbalance)
        goto next;
#endif
<variant 2>

If somebody has any preferences or concerns, please comment, i will
re-spin the patch.

--
Uladzislau Rezki