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

Yury Norov
2023-12-12T04:21:16Z

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