linux-kernel - Re: [RFC PATCH v2 1/6] sched/fair: Create util_fits

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Message-ID: <0184b049-9333-2b6b-09a0-bdb71f491e25@arm.com>
Date:   Thu, 12 Apr 2018 10:20:05 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Quentin Perret <quentin.perret@....com>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        linux-pm@...r.kernel.org,
        Morten Rasmussen <morten.rasmussen@....com>,
        Chris Redpath <chris.redpath@....com>,
        Patrick Bellasi <patrick.bellasi@....com>,
        Valentin Schneider <valentin.schneider@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steve Muckle <smuckle@...gle.com>,
        Eduardo Valentin <edubezval@...il.com>
Subject: Re: [RFC PATCH v2 1/6] sched/fair: Create util_fits_capacity()

On 04/12/2018 09:02 AM, Viresh Kumar wrote:
> On 06-04-18, 16:36, Dietmar Eggemann wrote:
>> The functionality that a given utilization fits into a given capacity
>> is factored out into a separate function.
>>
>> Currently it is only used in wake_cap() but will be re-used to figure
>> out if a cpu or a scheduler group is over-utilized.
>>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
>> ---
>>   kernel/sched/fair.c | 7 ++++++-
>>   1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 0951d1c58d2f..0a76ad2ef022 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -6574,6 +6574,11 @@ static unsigned long cpu_util_wake(int cpu, struct task_struct *p)
>>   	return min_t(unsigned long, util, capacity_orig_of(cpu));
>>   }
>>   
>> +static inline int util_fits_capacity(unsigned long util, unsigned long capacity)
>> +{
>> +	return capacity * 1024 > util * capacity_margin;
> 
> This changes the behavior slightly compared to existing code. If that
> wasn't intentional, perhaps you should use >= here.

You're right here ... Already on our v3 list. Thanks!

The 'misfit' patch-set comes with a similar function 
task_fits_capacity() so we have to align on this one with this patch-set 
as well.

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