linux-kernel - [PATCH v4 0/5] Make find_later_rq() choose a closer cpu in topology

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Date:   Fri, 12 May 2017 14:48:44 +0900
From:   Byungchul Park <byungchul.park@....com>
To:     <peterz@...radead.org>, <mingo@...nel.org>
CC:     <linux-kernel@...r.kernel.org>, <juri.lelli@...il.com>,
        <rostedt@...dmis.org>, <bristot@...hat.com>, <kernel-team@....com>
Subject: [PATCH v4 0/5] Make find_later_rq() choose a closer cpu in topology

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

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.

Byungchul Park (5):
  sched/deadline: Refer to cpudl.elements atomically
  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 | 46 +++++++++++++++++++++++++++++++-------------
 kernel/sched/deadline.c    | 48 +++++++++++++++++++++++++++++++---------------
 kernel/sched/rt.c          | 17 ++++++++++++++++
 3 files changed, 83 insertions(+), 28 deletions(-)

-- 
1.9.1