linux-kernel - Re: [PATCH v17 31/33] fs/resctrl: Introduce the interface to switch between monitor modes

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Message-ID: <29743495-f16f-4844-9121-49b510390cea@intel.com>
Date: Tue, 2 Sep 2025 20:11:55 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <tony.luck@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <Dave.Martin@....com>, <james.morse@....com>, <x86@...nel.org>,
	<hpa@...or.com>, <akpm@...ux-foundation.org>, <rostedt@...dmis.org>,
	<paulmck@...nel.org>, <pawan.kumar.gupta@...ux.intel.com>, <kees@...nel.org>,
	<arnd@...db.de>, <fvdl@...gle.com>, <seanjc@...gle.com>,
	<thomas.lendacky@....com>, <yosry.ahmed@...ux.dev>, <xin@...or.com>,
	<sohil.mehta@...el.com>, <kai.huang@...el.com>, <xiaoyao.li@...el.com>,
	<peterz@...radead.org>, <mario.limonciello@....com>, <xin3.li@...el.com>,
	<perry.yuan@....com>, <chang.seok.bae@...el.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<peternewman@...gle.com>, <eranian@...gle.com>, <gautham.shenoy@....com>
Subject: Re: [PATCH v17 31/33] fs/resctrl: Introduce the interface to switch
 between monitor modes

Hi Babu,

On 8/14/25 7:25 PM, Babu Moger wrote:
> Resctrl subsystem can support two monitoring modes, "mbm_event" or
> "default". In mbm_event mode, monitoring event can only accumulate data
> while it is backed by a hardware counter. In "default" mode, resctrl
> assumes there is a hardware counter for each event within every CTRL_MON
> and MON group.
> 
> Introduce mbm_assign_mode resctrl file to switch between mbm_event and
> default modes.
> 
> Example:
> To list the MBM monitor modes supported:
> $ cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> [mbm_event]
> default
> 
> To enable the "mbm_event" counter assignment mode:
> $ echo "mbm_event" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> 
> To enable the "default" monitoring mode:
> $ echo "default" > /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> 
> MBM event counters are automatically reset as part of changing the mode.

Needs imperative, eg.: "Reset MBM event counters automatically ..."

> Clear both architectural and non-architectural event states to prevent
> overflow conditions during the next event read. Clear assignable counter
> configuration on all the domains. Also, enable auto assignment when
> switching to "mbm_event" mode.
> 
> Signed-off-by: Babu Moger <babu.moger@....com>
> ---

| Reviewed-by: Reinette Chatre <reinette.chatre@...el.com>

Reinette