linux-kernel - Re: [PATCH 1/4 v4] sched/pelt: Move pelt related code in a dedicated file

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Message-ID: <3dfcbb67-746f-87b5-6167-6e5e220c4a69@arm.com>
Date:   Sun, 15 Apr 2018 15:27:59 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, rjw@...ysocki.net,
        Juri Lelli <juri.lelli@...hat.com>,
        Morten Rasmussen <Morten.Rasmussen@....com>,
        viresh kumar <viresh.kumar@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>
Subject: Re: [PATCH 1/4 v4] sched/pelt: Move pelt related code in a dedicated
 file

On 04/15/2018 02:16 PM, Vincent Guittot wrote:
> On 15 April 2018 at 13:58, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>> On 03/16/2018 12:25 PM, Vincent Guittot wrote:
>>>
>>> We want to track rt_rq's utilization as a part of the estimation of the
>>> whole rq's utilization. This is necessary because rt tasks can steal
>>> utilization to cfs tasks and make them lighter than they are.
>>> As we want to use the same load tracking mecanism for both and prevent
>>> useless dependency between cfs and rt code, pelt code is moved in a
>>> dedicated file.
>>
>>
>> This would mean that we introduce function calls into the cfs scheduler
>> fast-path, something we avoided so far (e.g. the cpu and frequency
>> invariance hooks). Are we OK with that?
>>
>> Quentin mentioned this already during v3 review back in December.
> 
> Yes and I hadn't seen any differences in the code size with the patch
> which should have been the case if inline function where replaced by
> function call

I see a diff (e.g. for arm64 defconfig):

6d626e0aaf91 - (HEAD -> tip/sched/core_rt_rq_util_tracking) sched/nohz: 
monitor rt utilization (2018-04-15 Vincent Guittot)
3111c6206f0c - cpufreq/schedutil: add rt utilization tracking 
(2018-04-15 Vincent Guittot)
62e103d266ed - sched/rt: add rt_rq utilization tracking (2018-04-15 
Vincent Guittot)
8f78fef6b1a2 - sched/pelt: Move pelt related code in a dedicated file 
(2018-04-15 Vincent Guittot)
31e77c93e432 - (tip/sched/core_rt_rq_util_tracking_base) sched/fair: 
Update blocked load when newly idle (2018-03-09 Vincent Guittot)

deggeman-mac:/opt/git/kernel_org:tip/sched/core_rt_rq_util_tracking$ 
size vmlinux
    text    data     bss     dec     hex filename
11286856        6154896  410296 17852048        1106690 vmlinux

versus:

31e77c93e432 - (HEAD -> tip/sched/core_rt_rq_util_tracking_base) 
sched/fair: Update blocked load when ne$
ly idle (2018-03-09 Vincent Guittot)

deggeman-mac:/opt/git/kernel_org:tip/sched/core_rt_rq_util_tracking_base$ 
size vmlinux
    text    data     bss     dec     hex filename 

11295048        6154896  410296 17860240        1108690 vmlinux

So I assume that in kernel/sched/fair.o:

U __update_load_avg_blocked_se
U __update_load_avg_cfs_rq
U __update_load_avg_se

are function calls now.