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

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Date:   Mon, 22 Aug 2022 15:36:08 +0800
From:   Yicong Yang <yangyicong@...wei.com>
To:     <peterz@...radead.org>, <mingo@...hat.com>,
        <juri.lelli@...hat.com>, <vincent.guittot@...aro.org>,
        <tim.c.chen@...ux.intel.com>, <gautham.shenoy@....com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>
CC:     <dietmar.eggemann@....com>, <rostedt@...dmis.org>,
        <bsegall@...gle.com>, <bristot@...hat.com>,
        <prime.zeng@...wei.com>, <yangyicong@...ilicon.com>,
        <jonathan.cameron@...wei.com>, <ego@...ux.vnet.ibm.com>,
        <srikar@...ux.vnet.ibm.com>, <linuxarm@...wei.com>,
        <21cnbao@...il.com>, <guodong.xu@...aro.org>,
        <hesham.almatary@...wei.com>, <john.garry@...wei.com>,
        <shenyang39@...wei.com>, <kprateek.nayak@....com>,
        <yu.c.chen@...el.com>, <wuyun.abel@...edance.com>
Subject: [PATCH v7 0/2] sched/fair: Scan cluster before scanning LLC in wake-up path

From: Yicong Yang <yangyicong@...ilicon.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(-)

-- 
2.24.0