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From: Joel Fernandes <joel.opensrc@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Valentin Schneider <valentin.schneider@arm.com>,
	Viresh Kumar <viresh.kumar@linaro.org>,
	Ingo Molnar <mingo@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Daniel Lezcano <daniel.lezcano@linaro.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Quentin Perret <quentin.perret@arm.com>,
	Joel Fernandes <joelaf@google.com>
Subject: Re: [PATCH] sched/fair: Rearrange select_task_rq_fair() to optimize it
Date: Tue, 24 Apr 2018 08:47:35 -0700	[thread overview]
Message-ID: <CAEi0qNmkkMEvbT+dJJqMwvRkQAw9xqKX65GKDZqtTAXUUxfs7Q@mail.gmail.com> (raw)
In-Reply-To: <CAEi0qN=qnej22F31jM2CMajee2h+ie0+AptFscwa5L8Arp8q3g@mail.gmail.com>

On Tue, Apr 24, 2018 at 8:46 AM, Joel Fernandes <joel.opensrc@gmail.com> wrote:
> On Tue, Apr 24, 2018 at 5:35 AM, Peter Zijlstra <peterz@infradead.org> wrote:
>> On Tue, Apr 24, 2018 at 12:19:07PM +0100, Valentin Schneider wrote:
>>> On 24/04/18 11:43, Peter Zijlstra wrote:
>>> > On Tue, Apr 24, 2018 at 11:02:26AM +0100, Valentin Schneider wrote:
>>> >> I'd argue making things easier to read is a non-negligible part as well.
>>> >
>>> > Right, so I don't object to either of these (I think); but it would be
>>> > good to see this in combination with that proposed EAS change.
>>> >
>>>
>>> True, I would've said the call to find_energy_efficient_cpu() ([1]) could
>>> simply be added to the if (sd) {} case, but...
>>
>> I think the proposal was to put it before the for_each_domain() loop
>> entirely, however...
>>
>>> > I think you (valentin) wanted to side-step the entire domain loop in
>>> > that case or something.
>>> >
>>>
>>> ...this would change more things. Admittedly I've been sort of out of the loop
>>> (no pun intended) lately, but this doesn't ring a bell. That might have been
>>> the other frenchie (Quentin) :)
>>
>> It does indeed appear I confused the two of you, it was Quentin playing
>> with that.
>>
>> In any case, if there not going to be conflicts here, this all looks
>> good.
>
> Both Viresh's and Valentin's patch looks lovely to me too. I couldn't
> spot anything wrong with them either. One suggestion I was thinking
> off is can we add better comments to this code (atleast label fast
> path vs slow path) ?
>
> Also, annotate the conditions for the fast/slow path with
> likely/unlikely since fast path is the common case? so like:
>
> if (unlikely(sd)) {
>   /* Fast path, common case */
>   ...
> } else if (...) {
>   /* Slow path */
> }

Aargh, I messed that up, I meant:

if (unlikely(sd)) {
   /* Slow path */
   ...
} else if (...) {
   /* Fast path */
}


thanks, :-)

- Joel

  reply	other threads:[~2018-04-24 15:47 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-23 10:38 Viresh Kumar
2018-04-24 10:02 ` Valentin Schneider
2018-04-24 10:30   ` Viresh Kumar
2018-04-24 10:43   ` Peter Zijlstra
2018-04-24 11:19     ` Valentin Schneider
2018-04-24 12:35       ` Peter Zijlstra
2018-04-24 15:46         ` Joel Fernandes
2018-04-24 15:47           ` Joel Fernandes [this message]
2018-04-24 22:34             ` Rohit Jain
2018-04-25  2:51               ` Viresh Kumar
2018-04-25 16:48                 ` Rohit Jain
2018-04-25  5:15         ` Viresh Kumar
2018-04-25  8:13           ` Quentin Perret
2018-04-25  9:03             ` Viresh Kumar
2018-04-25  9:39               ` Quentin Perret
2018-04-25 10:13                 ` Viresh Kumar
2018-04-25 10:55                   ` Quentin Perret
2018-04-25  8:12         ` Quentin Perret

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