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SubjectRe: [PATCH v5 0/4] Make find_later_rq() choose a closer cpu in topology
On Tue, May 23, 2017 at 11:00:55AM +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.

Hi, Peterz,

I wonder if you remember what I answered your question about applying
this approach into rt policy. Rt *already* works as expected.

And I implemented what you suggested, SD_PREFER_SIBLING. It would be
appriciated to check if I works correctly.

Thank you,
Byungchul

>
> Change from v4
> -. remove a patch that might cause huge lock contention
> (by spin lock(&cpudl.lock) in a hot path of scheduler)
>
> Change from v3
> -. rename closest_cpu to best_cpu so that it align with rt
> -. protect referring cpudl.elements with cpudl.lock
> -. change return value of cpudl_find() to bool
>
> Change from v2
> -. add support for SD_PREFER_SIBLING
>
> Change from v1
> -. clean up the patch
>
> Byungchul Park (4):
> sched/deadline: Make find_later_rq() choose a closer cpu in topology
> sched/deadline: Change return value of cpudl_find()
> sched/deadline: Add support for SD_PREFER_SIBLING on find_later_rq()
> sched/rt: Add support for SD_PREFER_SIBLING on find_lowest_rq()
>
> kernel/sched/cpudeadline.c | 26 ++++++++++++-------------
> kernel/sched/deadline.c | 48 +++++++++++++++++++++++++++++++---------------
> kernel/sched/rt.c | 17 ++++++++++++++++
> 3 files changed, 63 insertions(+), 28 deletions(-)
>
> --
> 1.9.1

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