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

[wangyanan (Y)]

On 2021/4/13 16:07, Yanan Wang wrote:
> Hi,
>
> 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.
>
> Description:
> 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.
>
> [0] 
> https://patchwork.kernel.org/project/qemu-devel/cover/20210225085627.2263-1-fangying1@huawei.com/
> [1] 
> https://kvmforum2020.sched.com/event/eE1y/virtual-topology-for-virtual-machines-friend-or-foe-dario-faggioli-suse
> [2] 
> https://github.com/rhdrjones/qemu/commit/ecfc1565f22187d2c715a99bbcd35cf3a7e428fa
>
> 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.

Thanks,
Yanan
> 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
>
> ---
>
> Changelogs:
> v1->v2:
> - 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(-)