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Re: [RFC PATCH v2 0/6] hw/arm/virt: Introduce cpu topology support

From: wangyanan (Y)
Subject: Re: [RFC PATCH v2 0/6] hw/arm/virt: Introduce cpu topology support
Date: Wed, 21 Apr 2021 17:31:48 +0800
User-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.4.0

On 2021/4/13 16:07, Yanan Wang wrote:

This series is a new version of [0] recently posted by Ying Fang
to introduce cpu topology support for ARM platform. I have taken
over his work about this now, thanks for his contribution.

An accurate cpu topology may help improve the cpu scheduler's decision
making when dealing with multi-core system. So cpu topology description
is helpful to provide guest with the right view. Dario Faggioli's talk
in [1] also shows the virtual topology could have impact on scheduling
performace. Thus this patch series introduces cpu topology support for
ARM platform.

This series originally comes from Andrew Jones's patches [2], but with
some re-arrangement. Thanks for Andrew's contribution. In this series,
both fdt and ACPI PPTT table are introduced to present cpu topology to
the guest. And a new function virt_smp_parse() not like the default
smp_parse() is introduced, which prefers cores over sockets.


Test results:
After applying this patch series, launch a guest with virt-6.0 and cpu
topology configured with: -smp 96,sockets=2,clusters=6,cores=4,threads=2,
Fix the incorrect statement:
Here the command line was "-smp 96, sockets=2, cores=24,threads=2" in reality.

VM's cpu topology description shows as below.

Architecture:        aarch64
Byte Order:          Little Endian
CPU(s):              96
On-line CPU(s) list: 0-95
Thread(s) per core:  2
Core(s) per socket:  24
Socket(s):           2
NUMA node(s):        1
Vendor ID:           0x48
Model:               0
Stepping:            0x1
BogoMIPS:            200.00
NUMA node0 CPU(s):   0-95


- Address Andrew Jones's comments
- Address Michael S. Tsirkin's comments
- Pick up one more patch(patch#6) of Andrew Jones
- Rebased on v6.0.0-rc2 release


Andrew Jones (3):
   device_tree: Add qemu_fdt_add_path
   hw/arm/virt: DT: Add cpu-map
   hw/arm/virt: Replace smp_parse with one that prefers cores

Yanan Wang (2):
   hw/acpi/aml-build: Add processor hierarchy node structure
   hw/arm/virt-acpi-build: Add PPTT table

Ying Fang (1):
   hw/arm/virt-acpi-build: Distinguish possible and present cpus

  hw/acpi/aml-build.c          |  27 ++++++++
  hw/arm/virt-acpi-build.c     |  77 ++++++++++++++++++++--
  hw/arm/virt.c                | 120 ++++++++++++++++++++++++++++++++++-
  include/hw/acpi/aml-build.h  |   4 ++
  include/hw/arm/virt.h        |   1 +
  include/sysemu/device_tree.h |   1 +
  softmmu/device_tree.c        |  45 ++++++++++++-
  7 files changed, 268 insertions(+), 7 deletions(-)

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