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    SubjectRe: [PATCH v6 0/2] Make find_later_rq() choose a closer cpu in topology
    On Thu, Aug 17, 2017 at 09:51:34PM -0700, Joel Fernandes (Google) wrote:
    > On Thu, Aug 17, 2017 at 6:25 PM, Byungchul Park <byungchul.park@lge.com> wrote:
    > > On Mon, Aug 07, 2017 at 12:50:32PM +0900, Byungchul Park wrote:
    > >> When cpudl_find() returns any among free_cpus, the cpu might not be
    > >> closer than others, considering sched domain. For example:
    > >>
    > >> this_cpu: 15
    > >> free_cpus: 0, 1,..., 14 (== later_mask)
    > >> best_cpu: 0
    > >>
    > >> topology:
    > >>
    > >> 0 --+
    > >> +--+
    > >> 1 --+ |
    > >> +-- ... --+
    > >> 2 --+ | |
    > >> +--+ |
    > >> 3 --+ |
    > >>
    > >> ... ...
    > >>
    > >> 12 --+ |
    > >> +--+ |
    > >> 13 --+ | |
    > >> +-- ... -+
    > >> 14 --+ |
    > >> +--+
    > >> 15 --+
    > >>
    > >> In this case, it would be best to select 14 since it's a free cpu and
    > >> closest to 15(this_cpu). However, currently the code select 0(best_cpu)
    > >> even though that's just any among free_cpus. Fix it.
    > >
    > > Could you let me know your opinions about this?
    >
    > Patch looks good to me, I would also add a comment ontop of
    > fallback_cpu (I think Steve mentioned similar thing at [1])
    >
    > /*
    > * fallback is the closest CPU in the closest SD incase
    > * all domains are PREFER_SIBLING
    > */
    > if (fallback_cpu == -1)
    > fallback_cpu = best_cpu;
    >
    > And clarify this in the commit message.

    Right. I will add it.

    Thank you very much,
    Byungchul

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