[PATCH v2] perf metricgroup: Avoid scanning unnecessary PMUs for identifier match

[Ian Rogers <irogers@google.com>]

Only uncore PMUs can have an identifier, so add an optimized
perf_pmus__scan routine for that case to avoid all PMU types being
created.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/perf/util/metricgroup.c | 11 +++--------
 tools/perf/util/pmus.c        | 18 +++++++++++++++++-
 tools/perf/util/pmus.h        |  1 +
 3 files changed, 21 insertions(+), 9 deletions(-)

diff --git a/tools/perf/util/metricgroup.c b/tools/perf/util/metricgroup.c
index 4db9578efd81..5a489e97c413 100644
--- a/tools/perf/util/metricgroup.c
+++ b/tools/perf/util/metricgroup.c
@@ -415,14 +415,9 @@ static int metricgroup__sys_event_iter(const struct pmu_metric *pm,
 	if (!pm->metric_expr || !pm->compat)
 		return 0;
 
-	while ((pmu = perf_pmus__scan(pmu))) {
-
-		if (!pmu->id || !pmu_uncore_identifier_match(pm->compat, pmu->id))
-			continue;
-
-		return d->fn(pm, table, d->data);
-	}
-	return 0;
+	/* Only process with the iterator if there is a a PMU that matches the ID. */
+	pmu = perf_pmus__scan_for_uncore_id(pmu, pm->compat);
+	return pmu ? d->fn(pm, table, d->data) : 0;
 }
 
 int metricgroup__for_each_metric(const struct pmu_metrics_table *table, pmu_metric_iter_fn fn,
diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index 9a2023ceeefd..5e3f571450fe 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -409,7 +409,7 @@ struct perf_pmu *perf_pmus__scan_matching_wildcard(struct perf_pmu *pmu, const c
 	if (!pmu) {
 		/*
 		 * Core PMUs, other sysfs PMUs and tool PMU can have any name or
-		 * aren't wother optimizing for.
+		 * aren't worth optimizing for.
 		 */
 		unsigned int to_read_pmus =  PERF_TOOL_PMU_TYPE_PE_CORE_MASK |
 			PERF_TOOL_PMU_TYPE_PE_OTHER_MASK |
@@ -486,6 +486,22 @@ static struct perf_pmu *perf_pmus__scan_skip_duplicates(struct perf_pmu *pmu)
 	return NULL;
 }
 
+struct perf_pmu *perf_pmus__scan_for_uncore_id(struct perf_pmu *pmu, const char *compat)
+{
+	if (!pmu) {
+		/* Only uncore PMUs can have identifiers. */
+		unsigned int to_read_pmus = PERF_TOOL_PMU_TYPE_PE_OTHER_MASK;
+
+		pmu_read_sysfs(to_read_pmus);
+		pmu = list_prepare_entry(pmu, &other_pmus, list);
+	}
+	list_for_each_entry_continue(pmu, &other_pmus, list) {
+		if (pmu->id && pmu_uncore_identifier_match(compat, pmu->id))
+			return pmu;
+	}
+	return NULL;
+}
+
 const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str)
 {
 	struct perf_pmu *pmu = NULL;
diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
index 7cb36863711a..0d55edb3f2fc 100644
--- a/tools/perf/util/pmus.h
+++ b/tools/perf/util/pmus.h
@@ -23,6 +23,7 @@ struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu);
 struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu);
 struct perf_pmu *perf_pmus__scan_for_event(struct perf_pmu *pmu, const char *event);
 struct perf_pmu *perf_pmus__scan_matching_wildcard(struct perf_pmu *pmu, const char *wildcard);
+struct perf_pmu *perf_pmus__scan_for_uncore_id(struct perf_pmu *pmu, const char *compat);
 
 const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
 
-- 
2.54.0.545.g6539524ca2-goog