Re: [PATCH 2/2] x86/resctrl: Fix memory bandwidth counter width for Hygon

[Xiaochen Shen]

Hi Tony,

On 12/7/2025 12:14 AM, Xiaochen Shen wrote:
>> Question: What is the value of "hw_res->mon_scale" on a Hygon system?
> I have double confirmed with Hygon hardware architect, in the testing Hygon system:
> hw_res->mon_scale: 64
> hw_res->mbm_width: 32
> 
> Here is a rough calculation for the theoretical max bandwidth by the hardware counter:
> (1) 32-bits width and mon_scale is 64:
> 2 ^32 * 64 = 2 ^38 = 256 (B/s)
> 

Sorry. Here is a typo:
- 2 ^32 * 64 = 2 ^38 = 256 (B/s)
+ 2 ^32 * 64 = 2 ^38 = 256G (B/s) 


> (2) 24-bits width and mon_scale is 64 (this is highly likely to cause overflow):
> 2 ^24 * 64 = 2 ^30 = 1G (B/s)


Best regards,
Xiaochen Shen