linux-kernel - Re: [PATCH v8 07/25] x86/resctrl: Introduce the interface to display monitor mode

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Message-ID: <a60a8998-419a-4263-a5d8-2defe70de549@amd.com>
Date: Mon, 14 Oct 2024 10:16:09 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>,
 "Luck, Tony" <tony.luck@...el.com>
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Subject: Re: [PATCH v8 07/25] x86/resctrl: Introduce the interface to display
 monitor mode

Hi Reinette,

On 10/11/24 17:24,  wrote:
> 
> 
> On 10/10/24 8:30 AM, Moger, Babu wrote:
>> On 10/10/24 10:07, Luck, Tony wrote:
>>>>>> +  By default resctrl assumes each control and monitor group has a hardware
>>>>>> +  counter. Hardware that does not support 'mbm_cntr_assign' mode will still
>>>>>> +  allow more control or monitor groups than 'num_rmids' to be created. In
>>>>>
>>>>> Should that be s/num_rmids/num_mbm_cntrs/ ?
>>>>
>>>> It is actually num_rmids here as in default mode, num_rmid_cntrs are not
>>>> available.
>>>
>>> Babu,
>>>
>>> The code isn't working that way for me. I built & booted. Since I'm on
>>> an Intel machine without ABMC I'm in "default" mode. But I can't make
>>> more monitor groups that num_rmids.
>>>
>>
>> That is correct. We will have to change the text. How about?
>>
>> "default":
>> By default resctrl assumes each control and monitor group has a hardware
>> counter. Hardware that does not support 'mbm_cntr_assign' mode will still
> 
> I think this is independent from whether hardware supports 'mbm_cntr_assign'
> mode since a user could enable 'default' mode on hardware that supports 
> 'mbm_cntr_assign'. This snippet is thus more about what is meant by 'default'
> mode than what is supported by hardware.
> 
> The docs already contain:
> 	"num_rmids":
> 		...
> 		This is the upper bound for how many "CTRL_MON" + "MON"
> 		groups can be created.
> 
> 
> Neither of the 'mbm_assign_mode' options change this meaning of 'num_rmids' (i.e.
> no change in how many monitor groups can be created) so mentioning it in the
> 'default' portion but not in the 'mbm_cntr_assign' portion may create confusion.
> 
> 
> Perhaps it can be simplified to:
> 	In default mode resctrl assumes each CTRL_MON and MON group has a
> 	hardware counter. Reading mbm_total_bytes or mbm_local_bytes may
> 	report 'Unavailable' if there is no counter associated with that
> 	group.

Sure.

-- 
Thanks
Babu Moger