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    SubjectRe: [PATCH] sched/fair: Rearrange select_task_rq_fair() to optimize it
    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

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