linux-kernel - Re: [RFC PATCH v3 03/17] x86/resctrl: Detect Assignable Bandwidth Monitoring feature details

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Date: Fri, 10 May 2024 12:01:40 -0500
From: "Moger, Babu" <bmoger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, 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: [RFC PATCH v3 03/17] x86/resctrl: Detect Assignable Bandwidth
 Monitoring feature details

Hi Reinette,

On 5/9/2024 10:18 PM, Reinette Chatre wrote:
> Hi Babu,
> 
> On 5/9/2024 3:34 PM, Moger, Babu wrote:
>> Hi Reinette,
>>
>> On 5/7/24 15:27, Reinette Chatre wrote:
>>> Hi Babu,
>>>
>>> On 5/6/2024 12:09 PM, Moger, Babu wrote:
>>>> On 5/3/24 18:26, Reinette Chatre wrote:
>>>>> On 3/28/2024 6:06 PM, Babu Moger wrote:
>>>
>>> ...
>>>
>>>>>> + * @mbm_assign_cntrs:	Maximum number of assignable counters
>>>>>>    */
>>>>>>   struct rdt_resource {
>>>>>>   	int			rid;
>>>>>> @@ -188,6 +198,8 @@ struct rdt_resource {
>>>>>>   	struct list_head	evt_list;
>>>>>>   	unsigned long		fflags;
>>>>>>   	bool			cdp_capable;
>>>>>> +	bool			mbm_assign_capable;
>>>>>> +	u32                     mbm_assign_cntrs;
>>>>>>   };
>>>>>
>>>>> Please check tabs vs spaces (in this whole series please).
>>>>
>>>> Sure. Will do.
>>>>
>>>>>
>>>>> I'm thinking that a new "MBM specific" struct within
>>>>> struct rdt_resource will be helpful to clearly separate the MBM related
>>>>> data. This will be similar to struct resctrl_cache for
>>>>> cache allocation and struct resctrl_membw for memory bandwidth
>>>>> allocation.
>>>>
>>>> Did you mean to move all the fields for monitoring to move to new struct?
>>>>
>>>> Struct resctrl_mbm {
>>>>            int                     num_rmid;
>>>>            bool                    mbm_assign_capable;
>>>>            u32                     mbm_assign_cntrs;
>>>> }:
>>>>
>>>
>>> Indeed, so not actually MBM specific but monitoring specific as you state (with
>>> appropriate naming?). This is purely to help organize data within struct rdt_resource
>>> and (similar to struct resctrl_cache and struct resctrl_membw) not a new
>>> structure expected to be passed around. I think evt_list can also be a member.
>>
>> How about this?
>>
>> Lets keep assign_capable in main structure(like we have mon_capable) and
>> move rest of them into new structure.
>>
>> Struct resctrl_mon {
>>             int                     num_rmid;
>> 	   struct list_head        evt_list;
>>             u32                     num_assign_cntrs;
>> }:
> 
> This looks like a good start. It certainly supports ABMC. I do not yet
> have a clear understanding about how this will support MPAM and soft-RMID/ABMC
> since the current implementation has an implicit scope of one counter per event per
> monitor group. It thus seem reasonable to have a new generic name of "cntrs".

How about renaming it to "assignable_counters"?

-- 
- Babu Moger