Re: [PATCH v13 00/32] x86,fs/resctrl telemetry monitoring

[Moger, Babu]

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@xxxxxxx/
> > >
> > > 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