linux-kernel - Re: [PATCH v11 00/23] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

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Message-ID: <698577f3-00c2-496c-b787-506cef589d26@amd.com>
Date: Tue, 18 Feb 2025 13:32:34 -0600
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 Dave Martin <Dave.Martin@....com>
Cc: Peter Newman <peternewman@...gle.com>, "Moger, Babu" <bmoger@....com>,
 corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com, tony.luck@...el.com, x86@...nel.org,
 hpa@...or.com, paulmck@...nel.org, akpm@...ux-foundation.org,
 thuth@...hat.com, rostedt@...dmis.org, xiongwei.song@...driver.com,
 pawan.kumar.gupta@...ux.intel.com, daniel.sneddon@...ux.intel.com,
 jpoimboe@...nel.org, perry.yuan@....com, sandipan.das@....com,
 kai.huang@...el.com, xiaoyao.li@...el.com, seanjc@...gle.com,
 xin3.li@...el.com, andrew.cooper3@...rix.com, ebiggers@...gle.com,
 mario.limonciello@....com, james.morse@....com, tan.shaopeng@...itsu.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 maciej.wieczor-retman@...el.com, eranian@...gle.com
Subject: Re: [PATCH v11 00/23] x86/resctrl : Support AMD Assignable Bandwidth
 Monitoring Counters (ABMC)

Hi Reinette,

On 2/18/25 12:14, Reinette Chatre wrote:
> Hi Babu,
> 
> On 2/18/25 7:39 AM, Moger, Babu wrote:
>  
>> 3. Use the actual events instead of flags based on the below comment.
>>
>> https://lore.kernel.org/lkml/a07fca4c-c8fa-41a6-b126-59815b9a58f9@intel.com/
>>
>>  Something like this.
>>  # echo '//0={mbm_total_bytes}{mbm_local_bytes};1={mbm_local_bytes}'
>>> /sys/fs/resctrl/info/L3_MON/mbm_assign_control
>>
>>  Are we ready to go with this approach? I am still not clear on this.
>>
>>  Reinette, What do you think?
> 
> I was actually expecting some push back or at least discussion on this interface
> because the braces seem difficult to parse when compared to, for example, using

I am yet to work on it. Will work on it after confirmation.

Here is the output from a system with 12 domains. I created one "test" group.

Output is definitely harder to parse for human eyes.

#cat info/L3_MON/mbm_assign_control
test//0={mbm_total_bytes}{mbm_local_bytes};1={mbm_total_bytes}{mbm_local_bytes};2={mbm_total_bytes}{mbm_local_bytes};3={mbm_total_bytes}{mbm_local_bytes};4={mbm_total_bytes}{mbm_local_bytes};5={mbm_total_bytes}{mbm_local_bytes};6={mbm_total_bytes}{mbm_local_bytes};7={mbm_total_bytes}{mbm_local_bytes};8={mbm_total_bytes}{mbm_local_bytes};9={mbm_total_bytes}{mbm_local_bytes};10={mbm_total_bytes}{mbm_local_bytes};11={mbm_total_bytes}{mbm_local_bytes}
//0={mbm_total_bytes}{mbm_local_bytes};1={mbm_total_bytes}{mbm_local_bytes};2={mbm_total_bytes}{mbm_local_bytes};3={mbm_total_bytes}{mbm_local_bytes};4={mbm_total_bytes}{mbm_local_bytes};5={mbm_total_bytes}{mbm_local_bytes};6={mbm_total_bytes}{mbm_local_bytes};7={mbm_total_bytes}{mbm_local_bytes};8={mbm_total_bytes}{mbm_local_bytes};9={mbm_total_bytes}{mbm_local_bytes};10={mbm_total_bytes}{mbm_local_bytes};11={mbm_total_bytes}{mbm_local_bytes}

It is harder to parse in code also. We should consider only if there is a
value-add with this format.

Otherwise I prefer our current flag format.

# cat info/L3_MON/mbm_assign_control
test//0=tl;1=tl;2=tl;3=tl;4=tl;5=tl;6=tl;7=tl;8=tl;9=tl;10=tl;11=tl
//0=tl;1=tl;2=tl;3=tl;4=tl;5=tl;6=tl;7=tl;8=tl;9=tl;10=tl;11=tl


> commas to separate the events of a domain. Peter [1] has some reservations about

Yes. I would like to hear from Peter.

> going this direction and since he would end up using this interface significantly
> I would prefer to resolve that first.
> 
> Reinette
> 
> 
> [1] https://lore.kernel.org/lkml/CALPaoCh7WpohzpXhSAbumjSZBv1_+1bXON7_V1pwG4bdEBr52Q@mail.gmail.com/
> 
> 

-- 
Thanks
Babu Moger