linux-kernel - Re: [PATCH v15 24/34] fs/resctrl: Report 'Unassigned' for MBM events in mbm

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Message-ID: <0fd87712-0a71-4f4b-8780-648099e708fa@intel.com>
Date: Tue, 22 Jul 2025 19:05:43 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: "Moger, Babu" <bmoger@....com>, <babu.moger@....com>, <corbet@....net>,
	<tony.luck@...el.com>, <james.morse@....com>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <x86@...nel.org>, <hpa@...or.com>,
	<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rostedt@...dmis.org>,
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	<fvdl@...gle.com>, <seanjc@...gle.com>, <jpoimboe@...nel.org>,
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	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>
Subject: Re: [PATCH v15 24/34] fs/resctrl: Report 'Unassigned' for MBM events
 in mbm_event mode

Hi Babu,

On 7/22/25 5:26 PM, Moger, Babu wrote:
> 
> There is no redundant text now. . Users can look up about "mbm_event" from "mbm_assign_mode". Here is the complete diff.
> 
> diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
> index 446736dbd97f..01c33f62ce74 100644
> --- a/Documentation/filesystems/resctrl.rst
> +++ b/Documentation/filesystems/resctrl.rst
> @@ -434,6 +434,12 @@ When monitoring is enabled all MON groups will also contain:
>         for the L3 cache they occupy). These are named "mon_sub_L3_YY"
>         where "YY" is the node number.
> 
> +       When the 'mbm_event' counter assignment mode is enabled, reading
> +       an MBM event of a MON group returns 'Unassigned' if no hardware
> +       counter is assigned to it. For CTRL_MON groups, 'Unassigned' is
> +       returned if none of the events in the CTRL_MON group or its
> +       associated MON groups have assigned counters.

The "none of the events" could be interpreted wrongly with only one MBM event
being read. How about the last sentence as:
	For CTRL_MON groups, 'Unassigned' is returned if the MBM event does not
	have an assigned counter in the CTRL_MON group nor in any of its associated
	MON groups.

Reinette