[RFC PATCH v3 00/16] Core scheduling v3

[Vineeth Remanan Pillai]

Third iteration of the Core-Scheduling feature.

This version fixes mostly correctness related issues in v2 and
addresses performance issues. Also, addressed some crashes related
to cgroups and cpu hotplugging.

We have tested and verified that incompatible processes are not
selected during schedule. In terms of performance, the impact
depends on the workload: 
- on CPU intensive applications that use all the logical CPUs with
  SMT enabled, enabling core scheduling performs better than nosmt.
- on mixed workloads with considerable io compared to cpu usage,
  nosmt seems to perform better than core scheduling.

Changes in v3
-------------
- Fixes the issue of sibling picking up an incompatible task
  - Aaron Lu
  - Vineeth Pillai
  - Julien Desfossez
- Fixes the issue of starving threads due to forced idle
  - Peter Zijlstra
- Fixes the refcounting issue when deleting a cgroup with tag
  - Julien Desfossez
- Fixes a crash during cpu offline/online with coresched enabled
  - Vineeth Pillai
- Fixes a comparison logic issue in sched_core_find
  - Aaron Lu

Changes in v2
-------------
- Fixes for couple of NULL pointer dereference crashes
  - Subhra Mazumdar
  - Tim Chen
- Improves priority comparison logic for process in different cpus
  - Peter Zijlstra
  - Aaron Lu
- Fixes a hard lockup in rq locking
  - Vineeth Pillai
  - Julien Desfossez
- Fixes a performance issue seen on IO heavy workloads
  - Vineeth Pillai
  - Julien Desfossez
- Fix for 32bit build
  - Aubrey Li

Issues
------
- Comparing process priority across cpus is not accurate

TODO
----
- Decide on the API for exposing the feature to userland

---

Peter Zijlstra (16):
  stop_machine: Fix stop_cpus_in_progress ordering
  sched: Fix kerneldoc comment for ia64_set_curr_task
  sched: Wrap rq::lock access
  sched/{rt,deadline}: Fix set_next_task vs pick_next_task
  sched: Add task_struct pointer to sched_class::set_curr_task
  sched/fair: Export newidle_balance()
  sched: Allow put_prev_task() to drop rq->lock
  sched: Rework pick_next_task() slow-path
  sched: Introduce sched_class::pick_task()
  sched: Core-wide rq->lock
  sched: Basic tracking of matching tasks
  sched: A quick and dirty cgroup tagging interface
  sched: Add core wide task selection and scheduling.
  sched/fair: Add a few assertions
  sched: Trivial forced-newidle balancer
  sched: Debug bits...

 include/linux/sched.h    |   9 +-
 kernel/Kconfig.preempt   |   7 +-
 kernel/sched/core.c      | 858 +++++++++++++++++++++++++++++++++++++--
 kernel/sched/cpuacct.c   |  12 +-
 kernel/sched/deadline.c  |  99 +++--
 kernel/sched/debug.c     |   4 +-
 kernel/sched/fair.c      | 180 ++++----
 kernel/sched/idle.c      |  42 +-
 kernel/sched/pelt.h      |   2 +-
 kernel/sched/rt.c        |  96 ++---
 kernel/sched/sched.h     | 237 ++++++++---
 kernel/sched/stop_task.c |  35 +-
 kernel/sched/topology.c  |   4 +-
 kernel/stop_machine.c    |   2 +
 14 files changed, 1250 insertions(+), 337 deletions(-)

-- 
2.17.1