[PATCH v3 00/24] sched: Introduce classes of tasks for load balance

[Ricardo Neri]

Hi,

This is third version of this patchset. Previous versions can be found
here [1] and here [2]. For brevity, I did not include the cover letter
from the original posting. You can read it here [1].

This patchset depends on a separate series to handle better asym_packing
between SMT cores [3].

For convenience, this patchset and [3] can be retrieved from [4] and are
based on the tip tree as on Feb 6th, 2023.

Changes since v2:

Ionela pointed out that the IPCC performance score was vague. I provided
a clearer definition and guidance on how architectures should implement
support for it.

Ionela mentioned that other architectures or scheduling schemes may want
to use IPC classes differently. I restricted its current use to
asym_packing.

Lukasz raised the issue that hardware may not be ready to support IPC
classes early after boot. I added a new interface that drivers or
enablement code can call to enable the use of IPC classes when ready.

Vincent provided multiple suggestions on how to balance non-SMT and SMT
sched groups. His feedback was incorporated in [3]. As a result, now
IPCC statistics are also used to break ties between fully_busy groups.

Dietmar indicated that real-time nor deadline tasks should influence the
CFS load balancing. I implemented such change. Also, as per his suggestion,
I folded the IPCC statistics into the existing struct sg_lb_stats.

Updated patches: 2, 6, 7, 10, 13, 14, 17
New patches: 9, 20
Unchanged patches: 1, 3, 4, 5, 8, 11, 12, 15, 16, 18, 19, 21, 22, 23, 24

Hopefully, this series is one step closer to be merged.

Thanks in advance for your kind feedback!

BR,
Ricardo

[1]. https://lore.kernel.org/lkml/20220909231205.14009-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/
[2]. https://lore.kernel.org/lkml/20221128132100.30253-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/
[3]. https://lore.kernel.org/lkml/20230207045838.11243-1-ricardo.neri-calderon@xxxxxxxxxxxxxxx/
[4]. https://github.com/ricardon/tip/tree/rneri/ipc_classes_v3

Ricardo Neri (24):
  sched/task_struct: Introduce IPC classes of tasks
  sched: Add interfaces for IPC classes
  sched/core: Initialize the IPC class of a new task
  sched/core: Add user_tick as argument to scheduler_tick()
  sched/core: Update the IPC class of the current task
  sched/fair: Collect load-balancing stats for IPC classes
  sched/fair: Compute IPC class scores for load balancing
  sched/fair: Use IPCC stats to break ties between asym_packing sched
    groups
  sched/fair: Use IPCC stats to break ties between fully_busy SMT groups
  sched/fair: Use IPCC scores to select a busiest runqueue
  thermal: intel: hfi: Introduce Intel Thread Director classes
  x86/cpufeatures: Add the Intel Thread Director feature definitions
  thermal: intel: hfi: Store per-CPU IPCC scores
  thermal: intel: hfi: Update the IPC class of the current task
  thermal: intel: hfi: Report the IPC class score of a CPU
  thermal: intel: hfi: Define a default class for unclassified tasks
  thermal: intel: hfi: Enable the Intel Thread Director
  sched/task_struct: Add helpers for IPC classification
  sched/core: Initialize helpers of task classification
  sched/fair: Introduce sched_smt_siblings_idle()
  thermal: intel: hfi: Implement model-specific checks for task
    classification
  x86/cpufeatures: Add feature bit for HRESET
  x86/hreset: Configure history reset
  x86/process: Reset hardware history in context switch

 arch/x86/include/asm/cpufeatures.h       |   2 +
 arch/x86/include/asm/disabled-features.h |   8 +-
 arch/x86/include/asm/hreset.h            |  30 +++
 arch/x86/include/asm/msr-index.h         |   6 +-
 arch/x86/include/asm/topology.h          |   8 +
 arch/x86/kernel/cpu/common.c             |  30 ++-
 arch/x86/kernel/cpu/cpuid-deps.c         |   1 +
 arch/x86/kernel/cpu/scattered.c          |   1 +
 arch/x86/kernel/process_32.c             |   3 +
 arch/x86/kernel/process_64.c             |   3 +
 drivers/thermal/intel/intel_hfi.c        | 242 +++++++++++++++++-
 include/linux/sched.h                    |  24 +-
 include/linux/sched/topology.h           |   6 +
 init/Kconfig                             |  12 +
 kernel/sched/core.c                      |  10 +-
 kernel/sched/fair.c                      | 309 ++++++++++++++++++++++-
 kernel/sched/sched.h                     |  66 +++++
 kernel/sched/topology.c                  |   9 +
 kernel/time/timer.c                      |   2 +-
 19 files changed, 751 insertions(+), 21 deletions(-)
 create mode 100644 arch/x86/include/asm/hreset.h

-- 
2.25.1