[PATCH v7 0/2] sched/fair: Scan cluster before scanning LLC in wake-up path

Yicong Yang
2022-08-22T07:38:23Z

From: Yicong Yang <yangyicong@hisilicon.com>

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 v6:
- rebase on 6.0-rc1
Link: https://lore.kernel.org/lkml/20220726074758.46686-1-yangyicong@huawei.com/

Change since v5:
- Improve patch 2 according to Peter's suggestion:
- use sched_cluster_active to indicate whether cluster is active
- consider SMT case and use wrap iteration when scanning cluster
- Add Vincent's tag
Thanks.
Link: https://lore.kernel.org/lkml/20220720081150.22167-1-yangyicong@hisilicon.com/

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@hisilicon.com/

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

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@hisilicon.com/

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@hisilicon.com/

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 | 30 +++++++++++++++++++++++++++---
kernel/sched/sched.h | 4 ++++
kernel/sched/topology.c | 25 +++++++++++++++++++++++++
6 files changed, 82 insertions(+), 4 deletions(-)

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2.24.0