[PATCH v3 0/7] lib/group_cpus: rework grp_spread_init_one() and make it O(1)

[Yury Norov <yury.norov@gmail.com>]

grp_spread_init_one() implementation is sub-optimal because it
traverses bitmaps from the beginning, instead of picking from the
previous iteration.

Fix it and use find_bit API where appropriate. While here, optimize
cpumasks allocation and drop unneeded cpumask_empty() call.

---
v1: https://lore.kernel.org/all/ZW5MI3rKQueLM0Bz@yury-ThinkPad/T/
v2: https://lore.kernel.org/lkml/ZXKNVRu3AfvjaFhK@fedora/T/
v3:
 - swap patches #2 and #3 @ Ming Lei;
 - add patch #7, which simplifies the function further.


Yury Norov (7):
  cpumask: introduce for_each_cpu_and_from()
  lib/group_cpus: optimize inner loop in grp_spread_init_one()
  lib/group_cpus: relax atomicity requirement in grp_spread_init_one()
  lib/group_cpus: optimize outer loop in grp_spread_init_one()
  lib/cgroup_cpus.c: don't zero cpumasks in group_cpus_evenly() on
    allocation
  lib/group_cpus.c: drop unneeded cpumask_empty() call in
    __group_cpus_evenly()
  lib/group_cpus: simplify grp_spread_init_one() for more

 include/linux/cpumask.h | 11 ++++++++++
 include/linux/find.h    |  3 +++
 lib/group_cpus.c        | 47 +++++++++++++++++------------------------
 3 files changed, 33 insertions(+), 28 deletions(-)

-- 
2.40.1