linux-kernel - Re: [PATCH v11 08/23] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <817b0c73-5898-4769-9356-a90435559f84@intel.com>
Date: Mon, 10 Feb 2025 10:08:20 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Moger, Babu" <bmoger@....com>, Babu Moger <babu.moger@....com>,
	<corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <tony.luck@...el.com>,
	<peternewman@...gle.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
	<akpm@...ux-foundation.org>, <thuth@...hat.com>, <rostedt@...dmis.org>,
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	<eranian@...gle.com>
Subject: Re: [PATCH v11 08/23] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Babu,

On 2/7/25 10:52 AM, Moger, Babu wrote:
> Hi Reinette,
> 
> On 2/7/2025 11:18 AM, Moger, Babu wrote:
>> Does this look ok? Just added domain in the text.
>>
>> "The number of monitoring counters available in each domain for assignment when the system supports mbm_cntr_assign mode.
>> ::
>>    # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
>>    32
>>
>> The resctrl file system supports tracking up to two memory bandwidth
>> events per monitoring group: mbm_total_bytes and/or mbm_local_bytes.
>> Up to two counters can be assigned per monitoring group, one for each
>> memory bandwidth event in each domain. More monitoring groups can be tracked by assigning one counter per monitoring group. However, doing so limits memory bandwidth tracking to a single memory bandwidth event per
>> monitoring group."
> 
> Revised again:
> 
> "The number of monitoring counters available in each domain for assignment when the system supports mbm_cntr_assign mode. For example, on a system with 32 monitoring counters:

I think we need to be careful with "available" since all these counters
may not be available. That is why "available_mbm_cntrs" exist.

How about something like (please feel free to improve):
"The maximum number of monitoring counters (total of available and assigned counters)
 in each domain when the system supports mbm_cntr_assign mode." 

Could you please make the "For example" a new paragraph (this follows existing style in the
docs). It could also be made more specific, for example,

"For example, on a system with 32 monitoring counters in each domain:"

> ::
>   # cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs
>   32
> 

The rest of the documentation seems like a repeat of what can be found in
the "mbm_assign_mode" section right above it. It does not look as though
any information will be lost by dropping the text below?

> The resctrl file system supports tracking up to two memory bandwidth
> events per monitoring group: mbm_total_bytes and/or mbm_local_bytes.
> Up to two counters can be assigned per monitoring group, one for each
> memory bandwidth event in each domain. More monitoring groups can be tracked by assigning one counter per monitoring group. However, doing so limits memory bandwidth tracking to a single memory bandwidth event per
> monitoring group."
> 
> Thanks
> Babu

Reinette