linux-kernel - [PATCH v4 0/2] Adjust NUMA imbalance for multiple LLCs

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Message-Id: <20211210093307.31701-1-mgorman@techsingularity.net>
Date:   Fri, 10 Dec 2021 09:33:05 +0000
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Aubrey Li <aubrey.li@...ux.intel.com>,
        Barry Song <song.bao.hua@...ilicon.com>,
        Mike Galbraith <efault@....de>,
        Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
        Gautham Shenoy <gautham.shenoy@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        Mel Gorman <mgorman@...hsingularity.net>
Subject: [PATCH v4 0/2] Adjust NUMA imbalance for multiple LLCs

Changelog since V3
o Calculate imb_numa_nr for multiple SD_NUMA domains
o Restore behaviour where communicating pairs remain on the same node

Commit 7d2b5dd0bcc4 ("sched/numa: Allow a floating imbalance between NUMA
nodes") allowed an imbalance between NUMA nodes such that communicating
tasks would not be pulled apart by the load balancer. This works fine when
there is a 1:1 relationship between LLC and node but can be suboptimal
for multiple LLCs if independent tasks prematurely use CPUs sharing cache.

The series addresses two problems -- inconsistent use of scheduler domain
weights and sub-optimal performance when there are many LLCs per NUMA node.

 include/linux/sched/topology.h |  1 +
 kernel/sched/fair.c            | 36 ++++++++++++++++---------------
 kernel/sched/topology.c        | 39 ++++++++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 17 deletions(-)

-- 
2.31.1

Mel Gorman (2):
  sched/fair: Use weight of SD_NUMA domain in find_busiest_group
  sched/fair: Adjust the allowed NUMA imbalance when SD_NUMA spans
    multiple LLCs

 include/linux/sched/topology.h |  1 +
 kernel/sched/fair.c            | 36 +++++++++++++++++----------------
 kernel/sched/topology.c        | 37 ++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 17 deletions(-)

-- 
2.31.1