linux-kernel - Re: [PATCH v8 08/25] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <ceeaf5a7-190e-4c29-89da-ba9e83693360@intel.com>
Date: Mon, 14 Oct 2024 09:25:33 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, Tony Luck <tony.luck@...el.com>
CC: <corbet@....net>, <fenghua.yu@...el.com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>,
	<x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<rdunlap@...radead.org>, <tj@...nel.org>, <peterz@...radead.org>,
	<yanjiewtw@...il.com>, <kim.phillips@....com>, <lukas.bulwahn@...il.com>,
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	<jpoimboe@...nel.org>, <rick.p.edgecombe@...el.com>,
	<kirill.shutemov@...ux.intel.com>, <jithu.joseph@...el.com>,
	<kai.huang@...el.com>, <kan.liang@...ux.intel.com>,
	<daniel.sneddon@...ux.intel.com>, <pbonzini@...hat.com>,
	<sandipan.das@....com>, <ilpo.jarvinen@...ux.intel.com>,
	<peternewman@...gle.com>, <maciej.wieczor-retman@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<eranian@...gle.com>, <james.morse@....com>
Subject: Re: [PATCH v8 08/25] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Babu and Tony,

On 10/10/24 8:12 AM, Moger, Babu wrote:
> 
> All good points. How about this text:
> 
> "num_mbm_cntrs":
> The number of monitoring counters available for assignment when the
> architecture supports mbm_cntr_assign mode.
> 
> Resctrl subsystem provides the interface to count maximum of two memory

subsystem -> filesystem

> bandwidth events per group, from a combination of available total and

Is this "from a combination of ..." snippet intended to hint at BMEC?

> local events. Keeping the current interface, users can enable a maximum of

What is meant by "Keeping the current interface"? Which interface? What will
"current" mean when a user reads this documentation?

> 2 counters per group. User will also have the option to enable only one

"User will also have" is talking about the future. When will this be the case?

> counter to the group to maximize the number of groups monitored.
> 
> 

I think that we need to be careful when making this documentation so specific
to the ABMC implementation. We already know that "soft-ABMC" is coming and
Peter already shared [1] that with software assignment it will not be possible
to assign counters to individual events. 

The goal of this work is to create a generic interface and this is the documentation
for it. If this documentation is created to be specific to the first implementation
it will make it difficult to use this same interface to support other
implementations.

Reinette

[1] https://lore.kernel.org/all/CALPaoCi_TBZnULHQpYns+H+30jODZvyQpUHJRDHNwjQzajrD=A@mail.gmail.com/