[PATCH v3 30/35] perf pmus: Allow just core PMU scanning

Ian Rogers
2023-05-24T22:22:14Z

Scanning all PMUs is expensive as all PMUs sysfs entries are loaded,
benchmarking shows more than 4x the cost:

```
$ perf bench internals pmu-scan -i 1000
Computing performance of sysfs PMU event scan for 1000 times
Average core PMU scanning took: 989.231 usec (+- 1.535 usec)
Average PMU scanning took: 4309.425 usec (+- 74.322 usec)
```

Add new perf_pmus__scan_core routine that scans just core
PMUs. Replace perf_pmus__scan calls with perf_pmus__scan_core when
non-core PMUs are being ignored.

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/arch/arm64/util/pmu.c | 5 +--
tools/perf/arch/x86/util/evlist.c | 5 +--
tools/perf/arch/x86/util/perf_regs.c | 8 ++---
tools/perf/bench/pmu-scan.c | 50 ++++++++++++++++------------
tools/perf/tests/pmu-events.c | 5 +--
tools/perf/util/cputopo.c | 12 +++----
tools/perf/util/header.c | 5 +--
tools/perf/util/mem-events.c | 14 ++------
tools/perf/util/parse-events.c | 13 +++-----
tools/perf/util/pmu.c | 10 ------
tools/perf/util/pmu.h | 2 --
tools/perf/util/pmus.c | 30 ++++++++++++-----
tools/perf/util/pmus.h | 1 +
tools/perf/util/print-events.c | 11 +++---
14 files changed, 75 insertions(+), 96 deletions(-)

diff --git a/tools/perf/arch/arm64/util/pmu.c b/tools/perf/arch/arm64/util/pmu.c
index 2504d43a39a7..561de0cb6b95 100644
--- a/tools/perf/arch/arm64/util/pmu.c
+++ b/tools/perf/arch/arm64/util/pmu.c
@@ -11,10 +11,7 @@ static struct perf_pmu *pmu__find_core_pmu(void)
{
struct perf_pmu *pmu = NULL;

- while ((pmu = perf_pmus__scan(pmu))) {
- if (!is_pmu_core(pmu->name))
- continue;
-
+ while ((pmu = perf_pmus__scan_core(pmu))) {
/*
* The cpumap should cover all CPUs. Otherwise, some CPUs may
* not support some events or have different event IDs.
diff --git a/tools/perf/arch/x86/util/evlist.c b/tools/perf/arch/x86/util/evlist.c
index 03240c640c7f..8a6a0b98b976 100644
--- a/tools/perf/arch/x86/util/evlist.c
+++ b/tools/perf/arch/x86/util/evlist.c
@@ -33,13 +33,10 @@ static int ___evlist__add_default_attrs(struct evlist *evlist,
continue;
}

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
struct perf_cpu_map *cpus;
struct evsel *evsel;

- if (!pmu->is_core)
- continue;
-
evsel = evsel__new(attrs + i);
if (evsel == NULL)
goto out_delete_partial_list;
diff --git a/tools/perf/arch/x86/util/perf_regs.c b/tools/perf/arch/x86/util/perf_regs.c
index befa7f3659b9..116384f19baf 100644
--- a/tools/perf/arch/x86/util/perf_regs.c
+++ b/tools/perf/arch/x86/util/perf_regs.c
@@ -300,11 +300,9 @@ uint64_t arch__intr_reg_mask(void)
* The same register set is supported among different hybrid PMUs.
* Only check the first available one.
*/
- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (pmu->is_core) {
- type = pmu->type;
- break;
- }
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
+ type = pmu->type;
+ break;
}
attr.config |= type << PERF_PMU_TYPE_SHIFT;
}
diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c
index 51cae2d03353..c7d207f8e13c 100644
--- a/tools/perf/bench/pmu-scan.c
+++ b/tools/perf/bench/pmu-scan.c
@@ -22,6 +22,7 @@ struct pmu_scan_result {
int nr_aliases;
int nr_formats;
int nr_caps;
+ bool is_core;
};

static const struct option options[] = {
@@ -53,6 +54,7 @@ static int save_result(void)
r = results + nr_pmus;

r->name = strdup(pmu->name);
+ r->is_core = pmu->is_core;
r->nr_caps = pmu->nr_caps;

r->nr_aliases = 0;
@@ -72,7 +74,7 @@ static int save_result(void)
return 0;
}

-static int check_result(void)
+static int check_result(bool core_only)
{
struct pmu_scan_result *r;
struct perf_pmu *pmu;
@@ -81,6 +83,9 @@ static int check_result(void)

for (int i = 0; i < nr_pmus; i++) {
r = &results[i];
+ if (core_only && !r->is_core)
+ continue;
+
pmu = perf_pmus__find(r->name);
if (pmu == NULL) {
pr_err("Cannot find PMU %s\n", r->name);
@@ -130,7 +135,6 @@ static int run_pmu_scan(void)
struct timeval start, end, diff;
double time_average, time_stddev;
u64 runtime_us;
- unsigned int i;
int ret;

init_stats(&stats);
@@ -142,26 +146,30 @@ static int run_pmu_scan(void)
return -1;
}

- for (i = 0; i < iterations; i++) {
- gettimeofday(&start, NULL);
- perf_pmus__scan(NULL);
- gettimeofday(&end, NULL);
-
- timersub(&end, &start, &diff);
- runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
- update_stats(&stats, runtime_us);
-
- ret = check_result();
- perf_pmus__destroy();
- if (ret < 0)
- break;
+ for (int j = 0; j < 2; j++) {
+ bool core_only = (j == 0);
+
+ for (unsigned int i = 0; i < iterations; i++) {
+ gettimeofday(&start, NULL);
+ if (core_only)
+ perf_pmus__scan_core(NULL);
+ else
+ perf_pmus__scan(NULL);
+ gettimeofday(&end, NULL);
+ timersub(&end, &start, &diff);
+ runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+ update_stats(&stats, runtime_us);
+
+ ret = check_result(core_only);
+ perf_pmus__destroy();
+ if (ret < 0)
+ break;
+ }
+ time_average = avg_stats(&stats);
+ time_stddev = stddev_stats(&stats);
+ pr_info(" Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n",
+ core_only ? " core" : "", time_average, time_stddev);
}
-
- time_average = avg_stats(&stats);
- time_stddev = stddev_stats(&stats);
- pr_info(" Average PMU scanning took: %.3f usec (+- %.3f usec)\n",
- time_average, time_stddev);
-
delete_result();
return 0;
}
diff --git a/tools/perf/tests/pmu-events.c b/tools/perf/tests/pmu-events.c
index 64ecb7845af4..64383fc34ef1 100644
--- a/tools/perf/tests/pmu-events.c
+++ b/tools/perf/tests/pmu-events.c
@@ -709,12 +709,9 @@ static int test__aliases(struct test_suite *test __maybe_unused,
struct perf_pmu *pmu = NULL;
unsigned long i;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
int count = 0;

- if (!is_pmu_core(pmu->name))
- continue;
-
if (list_empty(&pmu->format)) {
pr_debug2("skipping testing core PMU %s\n", pmu->name);
continue;
diff --git a/tools/perf/util/cputopo.c b/tools/perf/util/cputopo.c
index 4578c26747e1..729142ec9a9a 100644
--- a/tools/perf/util/cputopo.c
+++ b/tools/perf/util/cputopo.c
@@ -477,10 +477,9 @@ struct hybrid_topology *hybrid_topology__new(void)
if (!perf_pmus__has_hybrid())
return NULL;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (pmu->is_core)
- nr++;
- }
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL)
+ nr++;
+
if (nr == 0)
return NULL;

@@ -489,10 +488,7 @@ struct hybrid_topology *hybrid_topology__new(void)
return NULL;

tp->nr = nr;
- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (!pmu->is_core)
- continue;
-
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
if (load_hybrid_node(&tp->nodes[i], pmu)) {
hybrid_topology__delete(tp);
return NULL;
diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
index fa3f7dbbd90e..c701cc474d79 100644
--- a/tools/perf/util/header.c
+++ b/tools/perf/util/header.c
@@ -1591,10 +1591,7 @@ static int write_pmu_caps(struct feat_fd *ff,
*/
if (perf_pmus__has_hybrid()) {
pmu = NULL;
- while ((pmu = perf_pmus__scan(pmu))) {
- if (!pmu->is_core)
- continue;
-
+ while ((pmu = perf_pmus__scan_core(pmu))) {
ret = __write_pmu_caps(ff, pmu, true);
if (ret < 0)
return ret;
diff --git a/tools/perf/util/mem-events.c b/tools/perf/util/mem-events.c
index 08ac3ea2e366..c5596230a308 100644
--- a/tools/perf/util/mem-events.c
+++ b/tools/perf/util/mem-events.c
@@ -136,10 +136,7 @@ int perf_mem_events__init(void)
} else {
struct perf_pmu *pmu = NULL;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (!pmu->is_core)
- continue;
-
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
scnprintf(sysfs_name, sizeof(sysfs_name),
e->sysfs_name, pmu->name);
e->supported |= perf_mem_event__supported(mnt, sysfs_name);
@@ -176,10 +173,7 @@ static void perf_mem_events__print_unsupport_hybrid(struct perf_mem_event *e,
char sysfs_name[100];
struct perf_pmu *pmu = NULL;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (!pmu->is_core)
- continue;
-
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
scnprintf(sysfs_name, sizeof(sysfs_name), e->sysfs_name,
pmu->name);
if (!perf_mem_event__supported(mnt, sysfs_name)) {
@@ -217,9 +211,7 @@ int perf_mem_events__record_args(const char **rec_argv, int *argv_nr,
return -1;
}

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (!pmu->is_core)
- continue;
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
rec_argv[i++] = "-e";
s = perf_mem_events__name(j, pmu->name);
if (s) {
diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
index be544f948be2..e0c3f2037477 100644
--- a/tools/perf/util/parse-events.c
+++ b/tools/perf/util/parse-events.c
@@ -453,15 +453,12 @@ int parse_events_add_cache(struct list_head *list, int *idx, const char *name,
const char *config_name = get_config_name(head_config);
const char *metric_id = get_config_metric_id(head_config);

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+ /* Legacy cache events are only supported by core PMUs. */
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
LIST_HEAD(config_terms);
struct perf_event_attr attr;
int ret;

- /* Skip unsupported PMUs. */
- if (!perf_pmu__supports_legacy_cache(pmu))
- continue;
-
if (parse_events__filter_pmu(parse_state, pmu))
continue;

@@ -1481,12 +1478,10 @@ int parse_events_add_numeric(struct parse_events_state *parse_state,
return __parse_events_add_numeric(parse_state, list, /*pmu=*/NULL,
type, config, head_config);

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
+ /* Wildcards on numeric values are only supported by core PMUs. */
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
int ret;

- if (!perf_pmu__supports_wildcard_numeric(pmu))
- continue;
-
if (parse_events__filter_pmu(parse_state, pmu))
continue;

diff --git a/tools/perf/util/pmu.c b/tools/perf/util/pmu.c
index 044f31f9d0ff..4dd40a38f6bf 100644
--- a/tools/perf/util/pmu.c
+++ b/tools/perf/util/pmu.c
@@ -1440,21 +1440,11 @@ bool perf_pmu__supports_legacy_cache(const struct perf_pmu *pmu)
return pmu->is_core;
}

-bool perf_pmu__supports_wildcard_numeric(const struct perf_pmu *pmu)
-{
- return pmu->is_core;
-}
-
bool perf_pmu__auto_merge_stats(const struct perf_pmu *pmu)
{
return !is_pmu_hybrid(pmu->name);
}

-bool perf_pmu__is_mem_pmu(const struct perf_pmu *pmu)
-{
- return pmu->is_core;
-}
-
bool perf_pmu__have_event(const struct perf_pmu *pmu, const char *name)
{
struct perf_pmu_alias *alias;
diff --git a/tools/perf/util/pmu.h b/tools/perf/util/pmu.h
index f1f3e8a2e00e..02fec0a7d4c8 100644
--- a/tools/perf/util/pmu.h
+++ b/tools/perf/util/pmu.h
@@ -223,9 +223,7 @@ void perf_pmu__del_formats(struct list_head *formats);
bool is_pmu_core(const char *name);
bool is_pmu_hybrid(const char *name);
bool perf_pmu__supports_legacy_cache(const struct perf_pmu *pmu);
-bool perf_pmu__supports_wildcard_numeric(const struct perf_pmu *pmu);
bool perf_pmu__auto_merge_stats(const struct perf_pmu *pmu);
-bool perf_pmu__is_mem_pmu(const struct perf_pmu *pmu);
bool perf_pmu__have_event(const struct perf_pmu *pmu, const char *name);

FILE *perf_pmu__open_file(struct perf_pmu *pmu, const char *name);
diff --git a/tools/perf/util/pmus.c b/tools/perf/util/pmus.c
index 4ef4fecd335f..de7fc36519c9 100644
--- a/tools/perf/util/pmus.c
+++ b/tools/perf/util/pmus.c
@@ -87,7 +87,7 @@ static struct perf_pmu *perf_pmu__find2(int dirfd, const char *name)
}

/* Add all pmus in sysfs to pmu list: */
-static void pmu_read_sysfs(void)
+static void pmu_read_sysfs(bool core_only)
{
int fd;
DIR *dir;
@@ -104,6 +104,8 @@ static void pmu_read_sysfs(void)
while ((dent = readdir(dir))) {
if (!strcmp(dent->d_name, ".") || !strcmp(dent->d_name, ".."))
continue;
+ if (core_only && !is_pmu_core(dent->d_name))
+ continue;
/* add to static LIST_HEAD(core_pmus) or LIST_HEAD(other_pmus): */
perf_pmu__find2(fd, dent->d_name);
}
@@ -135,7 +137,7 @@ struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu)
bool use_core_pmus = !pmu || pmu->is_core;

if (!pmu) {
- pmu_read_sysfs();
+ pmu_read_sysfs(/*core_only=*/false);
pmu = list_prepare_entry(pmu, &core_pmus, list);
}
if (use_core_pmus) {
@@ -150,6 +152,18 @@ struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu)
return NULL;
}

+struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu)
+{
+ if (!pmu) {
+ pmu_read_sysfs(/*core_only=*/true);
+ pmu = list_prepare_entry(pmu, &core_pmus, list);
+ }
+ list_for_each_entry_continue(pmu, &core_pmus, list)
+ return pmu;
+
+ return NULL;
+}
+
const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str)
{
struct perf_pmu *pmu = NULL;
@@ -176,10 +190,10 @@ int perf_pmus__num_mem_pmus(void)
struct perf_pmu *pmu = NULL;
int count = 0;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (perf_pmu__is_mem_pmu(pmu))
- count++;
- }
+ /* All core PMUs are for mem events. */
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL)
+ count++;
+
return count;
}

@@ -421,8 +435,8 @@ bool perf_pmus__has_hybrid(void)
if (!hybrid_scanned) {
struct perf_pmu *pmu = NULL;

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- if (pmu->is_core && is_pmu_hybrid(pmu->name)) {
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
+ if (is_pmu_hybrid(pmu->name)) {
has_hybrid = true;
break;
}
diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
index 2a771d9f8da7..9de0222ed52b 100644
--- a/tools/perf/util/pmus.h
+++ b/tools/perf/util/pmus.h
@@ -11,6 +11,7 @@ struct perf_pmu *perf_pmus__find(const char *name);
struct perf_pmu *perf_pmus__find_by_type(unsigned int type);

struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu);
+struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu);

const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);

diff --git a/tools/perf/util/print-events.c b/tools/perf/util/print-events.c
index 9cee7bb7a561..7a5f87392720 100644
--- a/tools/perf/util/print-events.c
+++ b/tools/perf/util/print-events.c
@@ -272,12 +272,11 @@ int print_hwcache_events(const struct print_callbacks *print_cb, void *print_sta
struct perf_pmu *pmu = NULL;
const char *event_type_descriptor = event_type_descriptors[PERF_TYPE_HW_CACHE];

- while ((pmu = perf_pmus__scan(pmu)) != NULL) {
- /*
- * Skip uncore PMUs for performance. PERF_TYPE_HW_CACHE type
- * attributes can accept software PMUs in the extended type, so
- * also skip.
- */
+ /*
+ * Only print core PMUs, skipping uncore for performance and
+ * PERF_TYPE_SOFTWARE that can succeed in opening legacy cache evenst.
+ */
+ while ((pmu = perf_pmus__scan_core(pmu)) != NULL) {
if (pmu->is_uncore || pmu->type == PERF_TYPE_SOFTWARE)
continue;

--
2.40.1.698.g37aff9b760-goog