Re: [PATCH v13 31/32] x86/resctrl: Add debugfs files to show telemetry aggregator status

Reinette Chatre
2025-11-13T22:53:36Z

Hi Tony,

On 10/29/25 9:21 AM, Tony Luck wrote:
> Each telemetry aggregator provides three status registers at the top
> end of MMIO space after all the per-RMID per-event counters:
>
> data_loss_count: This counts the number of times that this aggregator
> failed to accumulate a counter value supplied by a CPU core.
>
> data_loss_timestamp: This is a "timestamp" from a free running
> 25MHz uncore timer indicating when the most recent data loss occurred.
>
> last_update_timestamp: Another 25MHz timestamp indicating when the
> most recent counter update was successfully applied.
>
> Create files in /sys/kernel/debug/resctrl/info/PERF_PKG_MON/x86_64/
> to display the value of each of these status registers for each aggregator
> in each enabled event group. The prefix for each file name describes
> the type of aggregator, which package it is located on, and an opaque
> instance number to provide a unique file name when there are multiple
> aggregators on a package.
>
> The suffix is one of the three strings listed above. An example name is:
>
> energy_pkg0_agg2_data_loss_count

Would files named like above have enough information when considering the
theoretical struct pmt_feature_group from patch #16? In that example there
are perf aggregators with two guids. As mentioned above the aggregator
instance is opaque so a user may not know which guid a file like above may
refer to.

Reinette