Re: [PATCH v1 00/12] CPU mask improvements/fixes particularly for hybrid

[James Clark <james.clark@linaro.org>]

On 27/06/2025 8:24 pm, Ian Rogers wrote:
> On hybrid systems some PMUs apply to all core types, particularly for
> metrics the msr PMU and the tsc event. The metrics often only want the
> values of the counter for their specific core type. These patches
> allow the cpu term in an event to give a PMU name to take the cpumask
> from. For example:
> 
>    $ perf stat -e msr/tsc,cpu=cpu_atom/ ...
> 
> will aggregate the msr/tsc/ value but only for atom cores. In doing
> this problems were identified in how cpumasks are handled by parsing
> and event setup when cpumasks are specified along with a task to
> profile. The event parsing, cpumask evlist propagation code and perf
> stat code are updated accordingly.
> 
> The final result of the patch series is to be able to run:
> ```
> $ perf stat --no-scale -e 'msr/tsc/,msr/tsc,cpu=cpu_core/,msr/tsc,cpu=cpu_atom/' perf test -F 10
>   10.1: Basic parsing test                                            : Ok
>   10.2: Parsing without PMU name                                      : Ok
>   10.3: Parsing with PMU name                                         : Ok
> 
>   Performance counter stats for 'perf test -F 10':
> 
>          63,704,975      msr/tsc/
>          47,060,704      msr/tsc,cpu=cpu_core/                        (4.62%)
>          16,640,591      msr/tsc,cpu=cpu_atom/                        (2.18%)
> ```
> 
> This has (further) identified a kernel bug for task events around the
> enabled time being too large leading to invalid scaling (hence the
>   --no-scale in the command line above).
> 
> Ian Rogers (12):
>    perf parse-events: Warn if a cpu term is unsupported by a CPU
>    perf stat: Avoid buffer overflow to the aggregation map
>    perf stat: Don't size aggregation ids from user_requested_cpus
>    perf parse-events: Allow the cpu term to be a PMU
>    perf tool_pmu: Allow num_cpus(_online) to be specific to a cpumask
>    libperf evsel: Rename own_cpus to pmu_cpus
>    libperf evsel: Factor perf_evsel__exit out of perf_evsel__delete
>    perf evsel: Use libperf perf_evsel__exit
>    perf pmus: Factor perf_pmus__find_by_attr out of evsel__find_pmu
>    perf parse-events: Minor __add_event refactoring
>    perf evsel: Add evsel__open_per_cpu_and_thread
>    perf parse-events: Support user CPUs mixed with threads/processes
> 
>   tools/lib/perf/evlist.c                 | 118 ++++++++++++++++--------
>   tools/lib/perf/evsel.c                  |   9 +-
>   tools/lib/perf/include/internal/evsel.h |   3 +-
>   tools/perf/builtin-stat.c               |   9 +-
>   tools/perf/tests/event_update.c         |   4 +-
>   tools/perf/util/evlist.c                |  15 +--
>   tools/perf/util/evsel.c                 |  55 +++++++++--
>   tools/perf/util/evsel.h                 |   5 +
>   tools/perf/util/expr.c                  |   2 +-
>   tools/perf/util/header.c                |   4 +-
>   tools/perf/util/parse-events.c          | 102 ++++++++++++++------
>   tools/perf/util/pmus.c                  |  29 +++---
>   tools/perf/util/pmus.h                  |   2 +
>   tools/perf/util/stat.c                  |   6 +-
>   tools/perf/util/synthetic-events.c      |   4 +-
>   tools/perf/util/tool_pmu.c              |  56 +++++++++--
>   tools/perf/util/tool_pmu.h              |   2 +-
>   17 files changed, 297 insertions(+), 128 deletions(-)
> 

Tested-by: James Clark <james.clark@linaro.org>