Re: [PATCH v3 0/2] perf stat: Fix uncore metric scaling across aggregation modes

[Chen, Zide]

On 5/21/2026 3:15 PM, Chun-Tse Shao wrote:
> This series fixes a scaling issue for metrics (like lpm_miss_lat) across
> different runtime aggregation modes.
> 
> Uncore metrics currently use `source_count` to scale events. However,
> `source_count` returns the total uncore unit count regardless of the
> selected aggregation mode. When evaluating metrics in different
> aggregation mode other than `--per-socket`, this incorrectly divides
> aggregated uncore events against the total uncore count rather than the
> uncores belonging to the aggregation, leading to wrong metric results.
> 
> To fix this, we:
> 1. Introduce the aggr_nr() keyword to the metric parser, which
> dynamically resolves to the active units in the current aggregation
> group (`gr->nr`).
> 
> 2. Update the python metrics to use `aggr_nr` instead of `source_count`,
> ensuring correct scaling across all runtime aggregation boundaries.
> 
> Before the fix (incorrect low latency in global mode):
>   $ perf stat -M lpm_miss_lat --metric-only -a -j -- sleep 1
>   {"ns  lpm_miss_lat_rem" : "122.8", "ns  lpm_miss_lat_loc" : "114.5"}
>   $ perf stat -M lpm_miss_lat --per-socket --metric-only -a -j -- sleep 1
>   {"socket" : "S0", "ns  lpm_miss_lat_rem" : "232.1", "ns  lpm_miss_lat_loc" : "278.2"}
>   {"socket" : "S1", "ns  lpm_miss_lat_rem" : "233.9", "ns  lpm_miss_lat_loc" : "257.5"}
> 
> After the fix (correct scaled latency in all aggregation modes):
>   $ perf stat -M lpm_miss_lat --metric-only -a -j -- sleep 1
>   {"ns  lpm_miss_lat_rem" : "231.7", "ns  lpm_miss_lat_loc" : "245.0"}
>   $ perf stat -M lpm_miss_lat --per-socket --metric-only -a -j -- sleep 1
>   {"socket" : "S0", "ns  lpm_miss_lat_rem" : "238.3", "ns  lpm_miss_lat_loc" : "249.4"}
>   {"socket" : "S1", "ns  lpm_miss_lat_rem" : "259.1", "ns  lpm_miss_lat_loc" : "253.1"}
> 
> v3:
>   Fixed based on Sashiko review:
>   - Removed the unnecessary, copied `redefined-builtin` pylint-disable
>     comment from `aggr_nr` definition inside `metric.py`.
> 
> v2: lore.kernel.org/20260521035941.3860145-1-ctshao@xxxxxxxxxx
>   Fixed based on Sashiko review:
>   - Fixed `aggr_nr` setting when an uncore event fails to run
>     (counts.run == 0) to explicitly set it to 0 instead of defaulting to
>     1.
>   - Accumulated `aggr_nr` when multiple unmerged PMU events are
>     associated with the same metric ID to prevent incorrect scaling
>     across active sockets.
>   - Removed unused `List` import from `typing` in `intel_metrics.py`.
> 
> v1: lore.kernel.org/20260520180032.3045144-1-ctshao@xxxxxxxxxx
> 
> Chun-Tse Shao (2):
>   perf stat: Add aggr_nr metric parser support
>   perf stat: Use aggr_nr scaling for Intel uncore miss latency metrics
> 
>  tools/perf/pmu-events/intel_metrics.py |  6 +++---
>  tools/perf/pmu-events/metric.py        |  9 +++++++--
>  tools/perf/util/expr.c                 | 26 ++++++++++++++++++++++----
>  tools/perf/util/expr.h                 |  6 +++++-
>  tools/perf/util/expr.l                 |  1 +
>  tools/perf/util/expr.y                 | 24 +++++++++++++++++-------
>  tools/perf/util/stat-shadow.c          |  6 +++++-
>  7 files changed, 60 insertions(+), 18 deletions(-)
> 
> --
> 2.54.0.746.g67dd491aae-goog

Tested the series on Intel CPUs.

Tested-by: Zide Chen <zide.chen@xxxxxxxxx>