linux-kernel - Re: [PATCH v9 14/26] x86/resctrl: Introduce interface to display number of free counters

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Message-ID: <ef92f1fb-086c-4ee1-b8ec-e08ed68f963a@amd.com>
Date: Fri, 22 Nov 2024 17:36:14 -0600
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, babu.moger@....com,
 corbet@....net, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: fenghua.yu@...el.com, x86@...nel.org, hpa@...or.com, thuth@...hat.com,
 paulmck@...nel.org, rostedt@...dmis.org, akpm@...ux-foundation.org,
 xiongwei.song@...driver.com, pawan.kumar.gupta@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, perry.yuan@....com, sandipan.das@....com,
 kai.huang@...el.com, xiaoyao.li@...el.com, seanjc@...gle.com,
 jithu.joseph@...el.com, brijesh.singh@....com, xin3.li@...el.com,
 ebiggers@...gle.com, andrew.cooper3@...rix.com, mario.limonciello@....com,
 james.morse@....com, tan.shaopeng@...itsu.com, tony.luck@...el.com,
 linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
 peternewman@...gle.com, maciej.wieczor-retman@...el.com, eranian@...gle.com,
 jpoimboe@...nel.org, thomas.lendacky@....com
Subject: Re: [PATCH v9 14/26] x86/resctrl: Introduce interface to display
 number of free counters

Hi Reinette,

On 11/21/2024 3:12 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 11/19/24 11:20 AM, Moger, Babu wrote:
>> Hi Reinette,
>>
>> On 11/15/24 18:31, Reinette Chatre wrote:
>>> Hi Babu,
>>>
>>> On 10/29/24 4:21 PM, Babu Moger wrote:
>>>> Provide the interface to display the number of free monitoring counters
>>>> available for assignment in each doamin when mbm_cntr_assign is supported.
>>>>
>>>> Signed-off-by: Babu Moger <babu.moger@....com>
>>>> ---
>>>> v9: New patch.
>>>> ---
>>>>   Documentation/arch/x86/resctrl.rst     |  4 ++++
>>>>   arch/x86/kernel/cpu/resctrl/monitor.c  |  1 +
>>>>   arch/x86/kernel/cpu/resctrl/rdtgroup.c | 33 ++++++++++++++++++++++++++
>>>>   3 files changed, 38 insertions(+)
>>>>
>>>> diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
>>>> index 2f3a86278e84..2bc58d974934 100644
>>>> --- a/Documentation/arch/x86/resctrl.rst
>>>> +++ b/Documentation/arch/x86/resctrl.rst
>>>> @@ -302,6 +302,10 @@ with the following files:
>>>>   	memory bandwidth tracking to a single memory bandwidth event per
>>>>   	monitoring group.
>>>>   
>>>> +"available_mbm_cntrs":
>>>> +	The number of free monitoring counters available assignment in each domain
>>>
>>> "The number of free monitoring counters available assignment" -> "The number of monitoring
>>> counters available for assignment"?
>>>
>>> (not taking into account how text may change after addressing Peter's feedback)
>>
>> How about this?
>>
>> "The number of monitoring counters available for assignment in each domain
>> when the architecture supports mbm_cntr_assign mode. There are a total of
>> "num_mbm_cntrs" counters are available for assignment. Counters can be
>> assigned or unassigned individually in each domain. A counter is available
>> for new assignment if it is unassigned in all domains."
> 
> Please consider the context of this paragraph. It follows right after the description
> of "num_mbm_cntrs" that states "Up to two counters can be assigned per monitoring group".
> I think it is confusing to follow that with a paragraph that states "Counters can be
> assigned or unassigned individually in each domain." I wonder if it may be helpful to
> use a different term ... for example a counter is *assigned* to an event of a monitoring
> group but this assignment may be to specified (not yet supported) or all (this work) domains while
> it is only *programmed*/*activated* to specified domains. Of course, all of this documentation
> needs to remain coherent if future work decides to indeed support per-domain assignment.
> 

Little bit lost here. Please help me.

"available_mbm_cntrs":
"The number of monitoring counters available for assignment in each 
domain when the architecture supports "mbm_cntr_assign" mode. There are 
a total of "num_mbm_cntrs" counters are available for assignment.
A counter is assigned to an event within a monitoring group and is 
available for activation across all domains. Users have the flexibility 
to activate it selectively within specific domains."

Thanks
- Babu Moger