Message-ID: <0d137f81-b3c0-4468-9a33-e521c6790bff@amd.com>
Date: Wed, 17 Dec 2025 10:44:29 -0600
From: "Moger, Babu" <bmoger@....com>
To: "Luck, Tony" <tony.luck@...el.com>
Cc: Fenghua Yu <fenghuay@...dia.com>,
 Reinette Chatre <reinette.chatre@...el.com>,
 Maciej Wieczor-Retman <maciej.wieczor-retman@...el.com>,
 Peter Newman <peternewman@...gle.com>, James Morse <james.morse@....com>,
 Babu Moger <babu.moger@....com>, Drew Fustini <dfustini@...libre.com>,
 Dave Martin <Dave.Martin@....com>, Chen Yu <yu.c.chen@...el.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH v13 00/32] x86,fs/resctrl telemetry monitoring

Hi Tony,

On 12/16/2025 6:28 PM, Luck, Tony wrote:
> On Wed, Nov 05, 2025 at 09:33:56AM -0600, Moger, Babu wrote:
>> Hi Tony,
>>
>> On 10/29/2025 1:59 PM, Luck, Tony wrote:
>>> I took a stab at applying the AET patches on tob of Babu's v10
>>> SDCIAE series https://lore.kernel.org/all/cover.1761090859.git.babu.moger@amd.com/
>>>
>>> There are only a couple of easy to resolve conflicts.
>>>
>>> I pushed a branch with v6.18-rc3 + SDCIAE + AET here:
>>>
>>> git://git.kernel.org/pub/scm/linux/kernel/git/aegl/linux.git sdciae-aet
>>>
>>
>> I ran your code on my AMD system. It appears to be working fine.
>> I don't have the hardware that supports these features. It would be helpful
>> to list the resctrl interface files (files in info directory and files each
>> group) and give an example of how it looks in the system that supports these
>> features. It can be in cover letter or resctrl.rst file as well. It will
>> also help to review the code.
> 
> Reinette reminded me that I didn't provide the examples that I promised.
> 
> 
> Here's what I plan to add to the v17 cover letter. Is this enough
> detail?
> 
> -Tony
> 
> 
> Examples:
> --------
> 
> As with other resctrl monitoring features first create CTRL_MON or MON
> directories and assign the tasks of interest to the group.
> 
> Energy events:
> -------------
> 
> There are two events associated with energy consumption in the core.
> The "core_energy" event reports out directly in Joules. To compute
> power just take the difference between two samples and divide by the
> time between them. E.g.
> 
> $ cat core_energy; sleep 10; cat core_energy

Please use the full path (/sys/fs/resctrl/test/mon_data/xx/<file_name>).

Otherwise looks good to me.

Thanks
Babu

> 94499439.510380
> 94499607.019680
> $ bc -q
> scale=3
> (94499607.019680 - 94499439.510380) / 10
> 16.750
> 
> So 16.75 Watts in this example.
> 
> Note that different runs of the same workload may report different
> energy consumption. This happens when cores shift to different
> voltage/frequency profiles due to overall system load.
> 
> The "activity" event reports energy usage in a manner independent
> of voltage and frequency. This may be useful for developers to
> assess how modifications to a program (e.g. attaching to a library
> optimized to use AVX instructions) affect energy consumption. So
> read the "activity" at the start and end of program execution and
> compute the difference.
> 
> Perf events:
> -----------
> 
> The other telemetry events largely duplicate events available using
> "perf", but avoid of reading the perf counters on every context switch.
> This may be a significant improvement when monitoring highly multi-threaded
> applications. E.g. to find the ratio of core cycles to reference cycles:
> 
> $ cat unhalted_core_cycles unhalted_ref_cycles
> 1312249223146571
> 1660157011698276
> $ { run application here }
> $ cat unhalted_core_cycles unhalted_ref_cycles
> 1313573565617233
> 1661511224019444
> $ bc -q
> scale = 3
> (1661511224019444 - 1660157011698276) / (1313573565617233 - 1312249223146571)
> 1.022
> 
> 

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