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perf pmu: Recognize 'default_core' as a core PMU and document matching

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The is_pmu_core function checks if a PMU name corresponds to a core
CPU PMU. However, it currently fails to recognize "default_core" as
a core PMU.

When "default_core" is used, the PMU scanning fallback in pmus.c
scans the "other_pmus" list. This scan is slow and always misses because
"default_core" is a core PMU, leading to unnecessary overhead.

Update is_pmu_core to recognize "default_core" directly. Additionally,
document the different matching approaches (exact name for x86/s390,
sysfs-based cpus file check for ARM/hybrid) to clarify how core PMUs are
classified.

Also, explicitly treat "default_core" as `all_pmus` in `setup_metric_events()`
to preserve the original metric resolution behavior for this pseudo-PMU.

Assisted-by: Gemini-CLI:Google Gemini 3.1 Pro
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Ian Rogers 2026-06-04 09:36:26 -07:00 committed by Arnaldo Carvalho de Melo
parent 536e81f074
commit be694c488a
2 changed files with 20 additions and 2 deletions
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3
tools/perf/util/metricgroup.c
View File

@ -295,7 +295,8 @@ static int setup_metric_events(const char *pmu, struct hashmap *ids,
const char *metric_id;
struct evsel *ev;
size_t ids_size, matched_events, i;
bool all_pmus = !strcmp(pmu, "all") || perf_pmus__num_core_pmus() == 1 || !is_pmu_core(pmu);
bool all_pmus = !strcmp(pmu, "all") || !strcmp(pmu, "default_core") ||
perf_pmus__num_core_pmus() == 1 || !is_pmu_core(pmu);
*out_metric_events = NULL;
ids_size = hashmap__size(ids);

19
tools/perf/util/pmu.c
View File

@ -2029,9 +2029,26 @@ int perf_pmu__for_each_format(struct perf_pmu *pmu, void *state, pmu_format_call
return 0;
}
/**
* is_pmu_core() - Check if the given PMU name corresponds to a core CPU PMU.
* @name: The PMU name to check.
*
* Core PMUs can be identified by:
* 1. Exact name match:
* - "cpu": Typically used on x86 architectures.
* - "cpum_cf": Typically used on s390 architectures (CPU Measurement Counter Facility).
* - "default_core": A generic name used to refer to the default core PMU.
* 2. Sysfs file existence check (is_sysfs_pmu_core):
* - Typically used on ARM systems or Intel hybrid architectures (e.g., "cpu_atom",
* "cpu_core"). This approach checks if the sysfs directory for the PMU
* contains a "cpus" file.
*/
bool is_pmu_core(const char *name)
{
return !strcmp(name, "cpu") || !strcmp(name, "cpum_cf") || is_sysfs_pmu_core(name);
return !strcmp(name, "cpu") ||
!strcmp(name, "cpum_cf") ||
!strcmp(name, "default_core") ||
is_sysfs_pmu_core(name);
}
bool perf_pmu__supports_legacy_cache(const struct perf_pmu *pmu)