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

[Chun-Tse Shao <ctshao@google.com>]

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 (`aggr->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" : "230.0", "ns  lpm_miss_lat_loc" : "220.8"}
  $ perf stat -M lpm_miss_lat --per-socket --metric-only -a -j -- sleep 1
  {"socket" : "S0", "ns  lpm_miss_lat_rem" : "232.5", "ns  lpm_miss_lat_loc" : "269.9"}
  {"socket" : "S1", "ns  lpm_miss_lat_rem" : "225.7", "ns  lpm_miss_lat_loc" : "262.3"}

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 |  8 ++++----
 tools/perf/pmu-events/metric.py        | 11 +++++++++--
 tools/perf/util/expr.c                 | 27 ++++++++++++++++++++++----
 tools/perf/util/expr.h                 |  4 ++++
 tools/perf/util/expr.l                 |  1 +
 tools/perf/util/expr.y                 | 24 ++++++++++++++++-------
 tools/perf/util/stat-shadow.c          |  4 +++-
 7 files changed, 61 insertions(+), 18 deletions(-)

--
2.54.0.669.g59709faab0-goog