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

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Message-ID: <23c04f34-eb70-e73a-7ec5-44a23f152d3b@amd.com>
Date: Fri, 27 Sep 2024 13:11:08 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 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 Reinette,

On 9/19/2024 1:00 PM, Reinette Chatre wrote:
> 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.

Agree. Peter/James, Please let me know if there are any concerns with 
the interface.

> 
>>
>> # 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"?

Sure.

> 
>>     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"

Sure.

> 
> Reinette
> 

Thanks
- Babu Moger