[PATCH v5 0/2] sched/fair: Scan cluster before scanning LLC in wake-up path

[Yicong Yang]

This is the follow-up work to support cluster scheduler. Previously
we have added cluster level in the scheduler for both ARM64[1] and
X86[2] to support load balance between clusters to bring more memory
bandwidth and decrease cache contention. This patchset, on the other
hand, takes care of wake-up path by giving CPUs within the same cluster
a try before scanning the whole LLC to benefit those tasks communicating
with each other.

[1] 778c558f49a2 ("sched: Add cluster scheduler level in core and related Kconfig for ARM64")
[2] 66558b730f25 ("sched: Add cluster scheduler level for x86")

Change since v4:
- rename cpus_share_resources to cpus_share_lowest_cache to be more informative, per Tim
- return -1 when nr==0 in scan_cluster(), per Abel
Thanks!
Link: https://lore.kernel.org/lkml/20220609120622.47724-1-yangyicong@xxxxxxxxxxxxx/

Change since v3:
- fix compile error when !CONFIG_SCHED_CLUSTER, reported by lkp test.
Link: https://lore.kernel.org/lkml/20220608095758.60504-1-yangyicong@xxxxxxxxxxxxx/

Change since v2:
- leverage SIS_PROP to suspend redundant scanning when LLC is overloaded
- remove the ping-pong suppression
- address the comment from Tim, thanks.
Link: https://lore.kernel.org/lkml/20220126080947.4529-1-yangyicong@xxxxxxxxxxxxx/

Change since v1:
- regain the performance data based on v5.17-rc1
- rename cpus_share_cluster to cpus_share_resources per Vincent and Gautham, thanks!
Link: https://lore.kernel.org/lkml/20211215041149.73171-1-yangyicong@xxxxxxxxxxxxx/

Barry Song (2):
  sched: Add per_cpu cluster domain info and cpus_share_lowest_cache API
  sched/fair: Scan cluster before scanning LLC in wake-up path

 include/linux/sched/sd_flags.h |  7 ++++++
 include/linux/sched/topology.h |  8 ++++++-
 kernel/sched/core.c            | 12 ++++++++++
 kernel/sched/fair.c            | 44 +++++++++++++++++++++++++++++++---
 kernel/sched/sched.h           |  2 ++
 kernel/sched/topology.c        | 15 ++++++++++++
 6 files changed, 84 insertions(+), 4 deletions(-)

-- 
2.24.0