linux-kernel - Re: [PATCH v9 09/26] x86/resctrl: Introduce interface to display number of monitoring counters

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Message-ID: <b6ef8e35-7acf-4391-9cab-76d7910435d7@intel.com>
Date: Fri, 15 Nov 2024 16:06:38 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <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>,
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	<maciej.wieczor-retman@...el.com>, <eranian@...gle.com>,
	<jpoimboe@...nel.org>, <thomas.lendacky@....com>
Subject: Re: [PATCH v9 09/26] x86/resctrl: Introduce interface to display
 number of monitoring counters

Hi Babu,

On 10/29/24 4:21 PM, Babu Moger wrote:
> The mbm_cntr_assign mode provides an option to the user to assign a
> counter to an RMID, event pair and monitor the bandwidth as long as
> the counter is assigned. Number of assignments depend on number of
> monitoring counters available.
> 
> Provide the interface to display the number of monitoring counters
> supported. The interface file 'num_mbm_cntrs' is available when an
> architecture supports mbm_cntr_assign mode.
> 

As mentioned in previous patch, do you think it may be possible to
have a value for num_mbm_cntrs for non-ABMC AMD systems? If that is
available and always exposed to user space (irrespective of
mbm_cntr_assign mode) then it would be clear to user space on
benefits/risks of running a "default" mode.

Reinette