[PATCH v2 7/7] perf pmu: Lazily compute default config

[Ian Rogers <irogers@google.com>]

The default config is computed during creation of the PMU and may do
things like scanning sysfs, when the PMU may just be used as part of
scanning. Change default_config to perf_event_attr_init_default, a
callback that is used when a default config needs initializing. This
avoids holding onto the memory for a perf_event_attr and copying.

On a tigerlake laptop running the pmu-scan benchmark:

Before:
Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 100 times
  Average core PMU scanning took: 28.780 usec (+- 0.503 usec)
  Average PMU scanning took: 283.480 usec (+- 18.471 usec)
Number of openat syscalls: 30,227

After:
Running 'internals/pmu-scan' benchmark:
Computing performance of sysfs PMU event scan for 100 times
  Average core PMU scanning took: 27.880 usec (+- 0.169 usec)
  Average PMU scanning took: 245.260 usec (+- 15.758 usec)
Number of openat syscalls: 28,914

Over 3 runs it is a nearly 12% reduction in execution time and a 4.3%
of openat calls.

Signed-off-by: Ian Rogers <irogers@google.com>
Reviewed-by: Adrian Hunter <adrian.hunter@intel.com>
---
 tools/perf/arch/arm/util/cs-etm.c    | 13 ++------
 tools/perf/arch/arm/util/pmu.c       |  4 +--
 tools/perf/arch/arm64/util/arm-spe.c | 45 ++++++++++++++--------------
 tools/perf/arch/x86/util/intel-pt.c  | 25 ++++++++--------
 tools/perf/arch/x86/util/pmu.c       |  2 +-
 tools/perf/util/arm-spe.h            |  4 ++-
 tools/perf/util/cs-etm.h             |  2 +-
 tools/perf/util/intel-pt.h           |  3 +-
 tools/perf/util/parse-events.c       | 12 ++++----
 tools/perf/util/pmu.c                |  3 +-
 tools/perf/util/pmu.h                |  7 +++--
 11 files changed, 58 insertions(+), 62 deletions(-)

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
index b8d6a953fd74..16bba74f048b 100644
--- a/tools/perf/arch/arm/util/cs-etm.c
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -917,16 +917,9 @@ struct auxtrace_record *cs_etm_record_init(int *err)
  * (CFG_CHG and evsel__set_config_if_unset()). If no default is set then user
  * changes aren't tracked.
  */
-struct perf_event_attr *
-cs_etm_get_default_config(struct perf_pmu *pmu __maybe_unused)
+void
+cs_etm_get_default_config(const struct perf_pmu *pmu __maybe_unused,
+			  struct perf_event_attr *attr)
 {
-	struct perf_event_attr *attr;
-
-	attr = zalloc(sizeof(struct perf_event_attr));
-	if (!attr)
-		return NULL;
-
 	attr->sample_period = 1;
-
-	return attr;
 }
diff --git a/tools/perf/arch/arm/util/pmu.c b/tools/perf/arch/arm/util/pmu.c
index f25f68f84a94..7f3af3b97f3b 100644
--- a/tools/perf/arch/arm/util/pmu.c
+++ b/tools/perf/arch/arm/util/pmu.c
@@ -20,12 +20,12 @@ void perf_pmu__arch_init(struct perf_pmu *pmu __maybe_unused)
 	if (!strcmp(pmu->name, CORESIGHT_ETM_PMU_NAME)) {
 		/* add ETM default config here */
 		pmu->selectable = true;
-		pmu->default_config = cs_etm_get_default_config(pmu);
+		pmu->perf_event_attr_init_default = cs_etm_get_default_config;
 #if defined(__aarch64__)
 	} else if (strstarts(pmu->name, ARM_SPE_PMU_NAME)) {
 		pmu->selectable = true;
 		pmu->is_uncore = false;
-		pmu->default_config = arm_spe_pmu_default_config(pmu);
+		pmu->perf_event_attr_init_default = arm_spe_pmu_default_config;
 	} else if (strstarts(pmu->name, HISI_PTT_PMU_NAME)) {
 		pmu->selectable = true;
 #endif
diff --git a/tools/perf/arch/arm64/util/arm-spe.c b/tools/perf/arch/arm64/util/arm-spe.c
index 08a76734ccd2..e3acc739bd00 100644
--- a/tools/perf/arch/arm64/util/arm-spe.c
+++ b/tools/perf/arch/arm64/util/arm-spe.c
@@ -113,6 +113,25 @@ arm_spe_snapshot_resolve_auxtrace_defaults(struct record_opts *opts,
 	}
 }
 
+static __u64 arm_spe_pmu__sample_period(const struct perf_pmu *arm_spe_pmu)
+{
+	static __u64 sample_period;
+
+	if (sample_period)
+		return sample_period;
+
+	/*
+	 * If kernel driver doesn't advertise a minimum,
+	 * use max allowable by PMSIDR_EL1.INTERVAL
+	 */
+	if (perf_pmu__scan_file(arm_spe_pmu, "caps/min_interval", "%llu",
+				&sample_period) != 1) {
+		pr_debug("arm_spe driver doesn't advertise a min. interval. Using 4096\n");
+		sample_period = 4096;
+	}
+	return sample_period;
+}
+
 static int arm_spe_recording_options(struct auxtrace_record *itr,
 				     struct evlist *evlist,
 				     struct record_opts *opts)
@@ -136,7 +155,7 @@ static int arm_spe_recording_options(struct auxtrace_record *itr,
 				return -EINVAL;
 			}
 			evsel->core.attr.freq = 0;
-			evsel->core.attr.sample_period = arm_spe_pmu->default_config->sample_period;
+			evsel->core.attr.sample_period = arm_spe_pmu__sample_period(arm_spe_pmu);
 			evsel->needs_auxtrace_mmap = true;
 			arm_spe_evsel = evsel;
 			opts->full_auxtrace = true;
@@ -495,26 +514,8 @@ struct auxtrace_record *arm_spe_recording_init(int *err,
 	return &sper->itr;
 }
 
-struct perf_event_attr
-*arm_spe_pmu_default_config(struct perf_pmu *arm_spe_pmu)
+void
+arm_spe_pmu_default_config(const struct perf_pmu *arm_spe_pmu, struct perf_event_attr *attr)
 {
-	struct perf_event_attr *attr;
-
-	attr = zalloc(sizeof(struct perf_event_attr));
-	if (!attr) {
-		pr_err("arm_spe default config cannot allocate a perf_event_attr\n");
-		return NULL;
-	}
-
-	/*
-	 * If kernel driver doesn't advertise a minimum,
-	 * use max allowable by PMSIDR_EL1.INTERVAL
-	 */
-	if (perf_pmu__scan_file(arm_spe_pmu, "caps/min_interval", "%llu",
-				  &attr->sample_period) != 1) {
-		pr_debug("arm_spe driver doesn't advertise a min. interval. Using 4096\n");
-		attr->sample_period = 4096;
-	}
-
-	return attr;
+	attr->sample_period = arm_spe_pmu__sample_period(arm_spe_pmu);
 }
diff --git a/tools/perf/arch/x86/util/intel-pt.c b/tools/perf/arch/x86/util/intel-pt.c
index 6d6cd8f9133c..fa0c718b9e72 100644
--- a/tools/perf/arch/x86/util/intel-pt.c
+++ b/tools/perf/arch/x86/util/intel-pt.c
@@ -60,7 +60,7 @@ struct intel_pt_recording {
 	size_t				priv_size;
 };
 
-static int intel_pt_parse_terms_with_default(struct perf_pmu *pmu,
+static int intel_pt_parse_terms_with_default(const struct perf_pmu *pmu,
 					     const char *str,
 					     u64 *config)
 {
@@ -84,7 +84,7 @@ static int intel_pt_parse_terms_with_default(struct perf_pmu *pmu,
 	return err;
 }
 
-static int intel_pt_parse_terms(struct perf_pmu *pmu, const char *str, u64 *config)
+static int intel_pt_parse_terms(const struct perf_pmu *pmu, const char *str, u64 *config)
 {
 	*config = 0;
 	return intel_pt_parse_terms_with_default(pmu, str, config);
@@ -177,7 +177,7 @@ static int intel_pt_pick_bit(int bits, int target)
 	return pick;
 }
 
-static u64 intel_pt_default_config(struct perf_pmu *intel_pt_pmu)
+static u64 intel_pt_default_config(const struct perf_pmu *intel_pt_pmu)
 {
 	char buf[256];
 	int mtc, mtc_periods = 0, mtc_period;
@@ -256,18 +256,17 @@ static int intel_pt_parse_snapshot_options(struct auxtrace_record *itr,
 	return 0;
 }
 
-struct perf_event_attr *
-intel_pt_pmu_default_config(struct perf_pmu *intel_pt_pmu)
+void intel_pt_pmu_default_config(const struct perf_pmu *intel_pt_pmu,
+				 struct perf_event_attr *attr)
 {
-	struct perf_event_attr *attr;
+	static u64 config;
+	static bool initialized;
 
-	attr = zalloc(sizeof(struct perf_event_attr));
-	if (!attr)
-		return NULL;
-
-	attr->config = intel_pt_default_config(intel_pt_pmu);
-
-	return attr;
+	if (!initialized) {
+		config = intel_pt_default_config(intel_pt_pmu);
+		initialized = true;
+	}
+	attr->config = config;
 }
 
 static const char *intel_pt_find_filter(struct evlist *evlist,
diff --git a/tools/perf/arch/x86/util/pmu.c b/tools/perf/arch/x86/util/pmu.c
index 949b3e2c67bd..469555ae9b3c 100644
--- a/tools/perf/arch/x86/util/pmu.c
+++ b/tools/perf/arch/x86/util/pmu.c
@@ -23,7 +23,7 @@ void perf_pmu__arch_init(struct perf_pmu *pmu __maybe_unused)
 	if (!strcmp(pmu->name, INTEL_PT_PMU_NAME)) {
 		pmu->auxtrace = true;
 		pmu->selectable = true;
-		pmu->default_config = intel_pt_pmu_default_config(pmu);
+		pmu->perf_event_attr_init_default = intel_pt_pmu_default_config;
 	}
 	if (!strcmp(pmu->name, INTEL_BTS_PMU_NAME)) {
 		pmu->auxtrace = true;
diff --git a/tools/perf/util/arm-spe.h b/tools/perf/util/arm-spe.h
index 98d3235781c3..4f4900c18f3e 100644
--- a/tools/perf/util/arm-spe.h
+++ b/tools/perf/util/arm-spe.h
@@ -27,5 +27,7 @@ struct auxtrace_record *arm_spe_recording_init(int *err,
 int arm_spe_process_auxtrace_info(union perf_event *event,
 				  struct perf_session *session);
 
-struct perf_event_attr *arm_spe_pmu_default_config(struct perf_pmu *arm_spe_pmu);
+void arm_spe_pmu_default_config(const struct perf_pmu *arm_spe_pmu,
+				struct perf_event_attr *attr);
+
 #endif
diff --git a/tools/perf/util/cs-etm.h b/tools/perf/util/cs-etm.h
index 7cca37887917..4696267a32f0 100644
--- a/tools/perf/util/cs-etm.h
+++ b/tools/perf/util/cs-etm.h
@@ -242,7 +242,7 @@ struct cs_etm_packet_queue {
 
 int cs_etm__process_auxtrace_info(union perf_event *event,
 				  struct perf_session *session);
-struct perf_event_attr *cs_etm_get_default_config(struct perf_pmu *pmu);
+void cs_etm_get_default_config(const struct perf_pmu *pmu, struct perf_event_attr *attr);
 
 enum cs_etm_pid_fmt {
 	CS_ETM_PIDFMT_NONE,
diff --git a/tools/perf/util/intel-pt.h b/tools/perf/util/intel-pt.h
index c7d6068e3a6b..18fd0be52e6c 100644
--- a/tools/perf/util/intel-pt.h
+++ b/tools/perf/util/intel-pt.h
@@ -42,6 +42,7 @@ struct auxtrace_record *intel_pt_recording_init(int *err);
 int intel_pt_process_auxtrace_info(union perf_event *event,
 				   struct perf_session *session);
 
-struct perf_event_attr *intel_pt_pmu_default_config(struct perf_pmu *pmu);
+void intel_pt_pmu_default_config(const struct perf_pmu *intel_pt_pmu,
+				 struct perf_event_attr *attr);
 
 #endif
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index c56e07bd7dd6..ea5579510b97 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -1418,11 +1418,10 @@ int parse_events_add_pmu(struct parse_events_state *parse_state,
 	}
 	fix_raw(&parsed_terms, pmu);
 
-	if (pmu->default_config) {
-		memcpy(&attr, pmu->default_config, sizeof(struct perf_event_attr));
-	} else {
-		memset(&attr, 0, sizeof(attr));
-	}
+	memset(&attr, 0, sizeof(attr));
+	if (pmu->perf_event_attr_init_default)
+		pmu->perf_event_attr_init_default(pmu, &attr);
+
 	attr.type = pmu->type;
 
 	if (list_empty(&parsed_terms.terms)) {
@@ -1466,7 +1465,8 @@ int parse_events_add_pmu(struct parse_events_state *parse_state,
 	 * When using default config, record which bits of attr->config were
 	 * changed by the user.
 	 */
-	if (pmu->default_config && get_config_chgs(pmu, &parsed_terms, &config_terms)) {
+	if (pmu->perf_event_attr_init_default &&
+	    get_config_chgs(pmu, &parsed_terms, &config_terms)) {
 		parse_events_terms__exit(&parsed_terms);
 		return -ENOMEM;
 	}
diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 8ef675ea7bdd..a967d25e899b 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1402,7 +1402,7 @@ int perf_pmu__config(struct perf_pmu *pmu, struct perf_event_attr *attr,
 		     struct parse_events_terms *head_terms,
 		     struct parse_events_error *err)
 {
-	bool zero = !!pmu->default_config;
+	bool zero = !!pmu->perf_event_attr_init_default;
 
 	return perf_pmu__config_terms(pmu, attr, head_terms, zero, err);
 }
@@ -2064,7 +2064,6 @@ void perf_pmu__delete(struct perf_pmu *pmu)
 
 	perf_cpu_map__put(pmu->cpus);
 
-	zfree(&pmu->default_config);
 	zfree(&pmu->name);
 	zfree(&pmu->alias_name);
 	zfree(&pmu->id);
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index 5a05131aa4ce..d2895d415f08 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -92,10 +92,11 @@ struct perf_pmu {
 	 */
 	int max_precise;
 	/**
-	 * @default_config: Optional default perf_event_attr determined in
-	 * architecture specific code.
+	 * @perf_event_attr_init_default: Optional function to default
+	 * initialize PMU specific parts of the perf_event_attr.
 	 */
-	struct perf_event_attr *default_config;
+	void (*perf_event_attr_init_default)(const struct perf_pmu *pmu,
+					     struct perf_event_attr *attr);
 	/**
 	 * @cpus: Empty or the contents of either of:
 	 * <sysfs>/bus/event_source/devices/<name>/cpumask.
-- 
2.42.0.655.g421f12c284-goog