linux-kernel - Re: [PATCH v7 00/24] x86/resctrl : Support AMD Assignable Bandwidth Monitoring Counters (ABMC)

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Message-ID: <6a806972-568a-4959-811d-7a666901da66@intel.com>
Date: Thu, 19 Sep 2024 11:00:26 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....com>, <corbet@....net>, <fenghua.yu@...el.com>,
	<tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>
CC: <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>,
	<seanjc@...gle.com>, <jmattson@...gle.com>, <leitao@...ian.org>,
	<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 v7 00/24] x86/resctrl : Support AMD Assignable Bandwidth
 Monitoring Counters (ABMC)

Hi Babu,

On 9/4/24 3:21 PM, Babu Moger wrote:
> # Linux Implementation
> 
> Create a generic interface aimed to support user space assignment
> of scarce counters used for monitoring. First usage of interface
> is by ABMC with option to expand usage to "soft-ABMC" and MPAM
> counters in future.
> 
> Feature adds following interface files:
> 
> /sys/fs/resctrl/info/L3_MON/mbm_assign_mode: Reports the list of assignable
> monitoring features supported. The enclosed brackets indicate which
> feature is enabled.
> 
> /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs: Reports the number of monitoring
> counters available for assignment.
> 
> /sys/fs/resctrl/info/L3_MON/mbm_assign_control: Reports the resctrl group and monitor
> status of each group. Assignment state can be updated by writing to the
> interface.

At this point I think the architecture is settling with the remaining work focusing
on polishing the code and making it more robust. To get confidence in this big addition
it will be valuable to hear from Peter and James to confirm if soft-ABMC and
MPAM can build on this.

> 
> # Examples
> 
> a. Check if ABMC support is available
> 	#mount -t resctrl resctrl /sys/fs/resctrl/
> 
> 	#cat /sys/fs/resctrl/info/L3_MON/mbm_assign_mode
> 	[mbm_cntr_assign]
> 	default
> 
> 	ABMC feature is detected and it is enabled.
> 
> b. Check how many ABMC counters are available. 
> 
> 	#cat /sys/fs/resctrl/info/L3_MON/num_mbm_cntrs 
> 	32
> 
> c. Create few resctrl groups.
> 
> 	# mkdir /sys/fs/resctrl/mon_groups/child_default_mon_grp
> 	# mkdir /sys/fs/resctrl/non_default_ctrl_mon_grp
> 	# mkdir /sys/fs/resctrl/non_default_ctrl_mon_grp/mon_groups/child_non_default_mon_grp
> 
> 
> d. This series adds a new interface file /sys/fs/resctrl/info/L3_MON/mbm_assign_control
>    to list and modify the group's monitoring states. File provides single place

"modify the group's monitoring states" -> "modify any group's monitoring states"?

>    to list monitoring states of all the resctrl groups. It makes it easier for
>    user space to to learn about the used counters without needing to traverse

"to to learn" -> "to learn"

Reinette