[PATCH 0/6] sched/numa: fix several NUMA balancing issues

[Li Zhe]

This series fixes several NUMA balancing issues around scan-period
adjustment, memory-tiering promotion feedback, and stale task-placement
state.

Patch 1 clears retained NUMA fault-window and locality state across
execve(), so the new image does not inherit feedback from the old one.

Patch 2 fixes the scan-period ratio denominator checks. The existing code
checks a different sum than the one later used as the divisor.

Patch 3 fixes scan-period adjustment for shared faults. Shared or local
faults should slow scanning down, while speeding up should require enough
faults that are both private and remote.

Patch 4 makes the free-space memory-tiering promotion bypass configurable.
The default behavior is preserved, but users can require the normal hotness
and rate-limit checks even when the top tier has enough free space.

Patch 5 prevents memory-tiering-only promotion faults from feeding normal
AutoNUMA task-placement statistics.

Patch 6 ignores stale preferred-node placement state while normal NUMA
balancing is disabled, so memory-tiering-only mode does not consume old
task-placement decisions.

Li Zhe (6):
  sched/numa: clear fault locality state on execve
  sched/numa: fix scan-period ratio denominator checks
  sched/numa: fix scan-period adjustment for shared faults
  sched/numa: make free-space tiering promotion bypass configurable
  sched/numa: do not feed tiering promotions into task placement stats
  sched/numa: ignore preferred nodes without normal balancing

 Documentation/admin-guide/sysctl/kernel.rst |  16 ++
 include/linux/mm.h                          |   5 +-
 include/linux/mmzone.h                      |   5 +-
 include/linux/sched.h                       |  17 +-
 kernel/sched/fair.c                         | 181 ++++++++++++++------
 mm/memory.c                                 |   2 +-
 6 files changed, 163 insertions(+), 63 deletions(-)

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2.20.1