Re: [PATCH v10 0/4] Support SMT control on arm64

[Yicong Yang]

On 2024/12/26 17:23, Shrikanth Hegde wrote:
> 
> 
> On 12/20/24 13:23, Yicong Yang wrote:
>> From: Yicong Yang <yangyicong@xxxxxxxxxxxxx>
>>
>> The core CPU control framework supports runtime SMT control which
>> is not yet supported on arm64. Besides the general vulnerabilities
>> concerns we want this runtime control on our arm64 server for:
>>
>> - better single CPU performance in some cases
>> - saving overall power consumption
>>
> 
> EAS is disabled when SMT is present.
> I am curious to know how power saving happens here.

EAS shouldn't work on non-asymmetic systems, so it's not the case here.
System wide power consumption comes down from the CPU offlining here.

Thanks.

> 
>> This patchset implements it in the following aspects:
>>
>> - Provides a default topology_is_primary_thread()
>> - support retrieve SMT thread number on OF based system
>> - support retrieve SMT thread number on ACPI based system
>> - select HOTPLUG_SMT for arm64
>>
>> Tests has been done on our ACPI based arm64 server and on ACPI/OF\
>> based QEMU VMs.
>>
> .