Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754216AbcKIQyT (ORCPT <rfc822;w@1wt.eu>);
        Wed, 9 Nov 2016 11:54:19 -0500
Received: from mail-yw0-f182.google.com ([209.85.161.182]:34929 "EHLO
        mail-yw0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1752065AbcKIQyR (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 9 Nov 2016 11:54:17 -0500
MIME-Version: 1.0
In-Reply-To: <20161019095350.GH3102@twins.programming.kicks-ass.net>
References: <CANRm+CyVFuT3XJt7DZEBZgHb_hQPzDUfOGnkAqNexH4q2ex74Q@mail.gmail.com>
 <20161010100107.GZ16071@codeblueprint.co.uk> <CAKfTPtBFrahA2fBoG5S5CBiJHb8EZkUbPaOZ4jZFc1mVYH5zJQ@mail.gmail.com>
 <20161010173440.GA28945@linaro.org> <20161011102453.GA16071@codeblueprint.co.uk>
 <20161018102937.GI16071@codeblueprint.co.uk> <20161018111017.GY3142@twins.programming.kicks-ass.net>
 <20161018112957.GJ16071@codeblueprint.co.uk> <20161018121557.GA3142@twins.programming.kicks-ass.net>
 <CAKfTPtBnpDMh=v6fxqtV0sTeFzVqK6HrAsVXvO0WZqrQTbxYng@mail.gmail.com> <20161019095350.GH3102@twins.programming.kicks-ass.net>
From: Vincent Guittot <vincent.guittot@linaro.org>
Date: Wed, 9 Nov 2016 17:53:56 +0100
Message-ID: <CAKfTPtDvy1pPunGQTe3hCRioUj1seJhqaVffiFVHM3-Lsn4oLw@mail.gmail.com>
Subject: Re: [PATCH] sched/fair: Do not decay new task load on first enqueue
To: Peter Zijlstra <peterz@infradead.org>
Cc: Matt Fleming <matt@codeblueprint.co.uk>,
        Wanpeng Li <kernellwp@gmail.com>, Ingo Molnar <mingo@kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Mike Galbraith <umgwanakikbuti@gmail.com>,
        Yuyang Du <yuyang.du@intel.com>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>
Content-Type: text/plain; charset=UTF-8
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 1912
Lines: 59

On 19 October 2016 at 11:53, Peter Zijlstra <peterz@infradead.org> wrote:
> On Wed, Oct 19, 2016 at 08:38:12AM +0200, Vincent Guittot wrote:
>> > It might make sense to have helper functions to evaluate those
>>
>> The main issue is the number of parameters used in these conditions
>> that makes helper function not really more readable.
>
> Fair enough I suppose..
>
>> > conditions, because currently there's two instances of each, once in the
>> > branch selection and then again (but inverted, we miss the == case fwiw)
>>
>> not sure to catch the comment about inverted and miss the == case
>
> Oh, you're right. Which proves my point on this not being entirely
> readable :/

Hi Peter,

I'm not sure of the status of this patch.
It seems difficult to get a more readable code.
Do you want me to add more comments about when we enter each state or
current version is enough ?

Vincent

>
> Initially I thought the things were of the form:
>
>         else if (ineq) {
>         }
>
>         ...
>
>         if (... || !ineq || ...)
>
>
> Which would get you things like: a<b, !a<b := a>b, and leave a==b
> undefined. But if I put them along side one another like:
>
>
> +               } else if (min_runnable_load > (runnable_load + imbalance)) {
>
> +                         (min_runnable_load > (this_runnable_load + imbalance)) ||
>
>
> +               } else if ((runnable_load < (min_runnable_load + imbalance)) &&
> +                               (100*min_avg_load > sd->imbalance_pct*avg_load)) {
>
> +                    ((this_runnable_load < (min_runnable_load + imbalance)) &&
> +                               (100*min_avg_load > sd->imbalance_pct*this_avg_load)))
>
> We can see this is not in fact the case.
>
> Blergh, I also cannot see a pretty way to increase readability here,
> because while they have the same general shape, there's this small
> variation with this_*.
>
> A well..