[PATCH 2/2] perf-stat: introduce config stat.bpf-counter-events

Song Liu
2021-04-03T00:31:00Z

Currently, to use BPF to aggregate perf event counters, the user uses
--bpf-counters option. Enable "use bpf by default" events with a config
option, stat.bpf-counter-events. This is limited to hardware events in
evsel__hw_names.

This also enables mixed BPF event and regular event in the same sesssion.
For example:

perf config stat.bpf-counter-events=instructions
perf stat -e instructions,cs

The second command will use BPF for "instructions" but not "cs".

Signed-off-by: Song Liu <song@kernel.org>
---
tools/perf/Documentation/perf-stat.txt | 2 ++
tools/perf/builtin-stat.c | 41 ++++++++++++++++----------
tools/perf/util/bpf_counter.c | 11 +++++++
tools/perf/util/config.c | 32 ++++++++++++++++++++
tools/perf/util/evsel.c | 2 ++
tools/perf/util/evsel.h | 1 +
tools/perf/util/target.h | 5 ----
7 files changed, 74 insertions(+), 20 deletions(-)

diff --git a/tools/perf/Documentation/perf-stat.txt b/tools/perf/Documentation/perf-stat.txt
index 744211fa8c186..6d4733eaac170 100644
--- a/tools/perf/Documentation/perf-stat.txt
+++ b/tools/perf/Documentation/perf-stat.txt
@@ -97,6 +97,8 @@ report::
Use BPF programs to aggregate readings from perf_events. This
allows multiple perf-stat sessions that are counting the same metric (cycles,
instructions, etc.) to share hardware counters.
+ To use BPF programs on common hardware events by default, use
+ "perf config stat.bpf-counter-events=<list_of_events>".

--bpf-attr-map::
With option "--bpf-counters", different perf-stat sessions share
diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 4bb48c6b66980..5adfa708ffe68 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -423,17 +423,28 @@ static int read_affinity_counters(struct timespec *rs)
return 0;
}

+/*
+ * Returns:
+ * 0 if all events use BPF;
+ * 1 if some events do NOT use BPF;
+ * < 0 on errors;
+ */
static int read_bpf_map_counters(void)
{
+ bool has_none_bpf_events = false;
struct evsel *counter;
int err;

evlist__for_each_entry(evsel_list, counter) {
+ if (!counter->bpf_counter_ops) {
+ has_none_bpf_events = true;
+ continue;
+ }
err = bpf_counter__read(counter);
if (err)
return err;
}
- return 0;
+ return has_none_bpf_events ? 1 : 0;
}

static void read_counters(struct timespec *rs)
@@ -442,9 +453,10 @@ static void read_counters(struct timespec *rs)
int err;

if (!stat_config.stop_read_counter) {
- if (target__has_bpf(&target))
- err = read_bpf_map_counters();
- else
+ err = read_bpf_map_counters();
+ if (err < 0)
+ return;
+ if (err)
err = read_affinity_counters(rs);
if (err < 0)
return;
@@ -535,12 +547,13 @@ static int enable_counters(void)
struct evsel *evsel;
int err;

- if (target__has_bpf(&target)) {
- evlist__for_each_entry(evsel_list, evsel) {
- err = bpf_counter__enable(evsel);
- if (err)
- return err;
- }
+ evlist__for_each_entry(evsel_list, evsel) {
+ if (!evsel->bpf_counter_ops)
+ continue;
+
+ err = bpf_counter__enable(evsel);
+ if (err)
+ return err;
}

if (stat_config.initial_delay < 0) {
@@ -784,11 +797,9 @@ static int __run_perf_stat(int argc, const char **argv, int run_idx)
if (affinity__setup(&affinity) < 0)
return -1;

- if (target__has_bpf(&target)) {
- evlist__for_each_entry(evsel_list, counter) {
- if (bpf_counter__load(counter, &target))
- return -1;
- }
+ evlist__for_each_entry(evsel_list, counter) {
+ if (bpf_counter__load(counter, &target))
+ return -1;
}

evlist__for_each_cpu (evsel_list, i, cpu) {
diff --git a/tools/perf/util/bpf_counter.c b/tools/perf/util/bpf_counter.c
index df70c8dcf7850..ea45914af1693 100644
--- a/tools/perf/util/bpf_counter.c
+++ b/tools/perf/util/bpf_counter.c
@@ -792,6 +792,17 @@ int bpf_counter__load(struct evsel *evsel, struct target *target)
evsel->bpf_counter_ops = &bpf_program_profiler_ops;
else if (target->use_bpf)
evsel->bpf_counter_ops = &bperf_ops;
+ else {
+ int i;
+
+ for (i = 0; i < PERF_COUNT_HW_MAX; i++) {
+ if (!strcmp(evsel->name, evsel__hw_names[i])) {
+ if (evsel__use_bpf_counters[i])
+ evsel->bpf_counter_ops = &bperf_ops;
+ break;
+ }
+ }
+ }

if (evsel->bpf_counter_ops)
return evsel->bpf_counter_ops->load(evsel, target);
diff --git a/tools/perf/util/config.c b/tools/perf/util/config.c
index 2daeaa9a4a241..fe2ec56258735 100644
--- a/tools/perf/util/config.c
+++ b/tools/perf/util/config.c
@@ -18,6 +18,7 @@
#include "util/hist.h" /* perf_hist_config */
#include "util/llvm-utils.h" /* perf_llvm_config */
#include "util/stat.h" /* perf_stat__set_big_num */
+#include "util/evsel.h" /* evsel__hw_names, evsel__use_bpf_counters */
#include "build-id.h"
#include "debug.h"
#include "config.h"
@@ -433,6 +434,29 @@ static int perf_buildid_config(const char *var, const char *value)
return 0;
}

+static int perf_stat_config_parse_bpf_counter_event(const char *value)
+{
+ char *event_str, *event_str_, *tok, *saveptr = NULL;
+ int i;
+
+ event_str_ = event_str = strdup(value);
+ if (!event_str)
+ return -1;
+
+ while ((tok = strtok_r(event_str, ",", &saveptr)) != NULL) {
+ for (i = 0; i < PERF_COUNT_HW_MAX; i++) {
+ if (!strcmp(tok, evsel__hw_names[i])) {
+ evsel__use_bpf_counters[i] = true;
+ break;
+ }
+ }
+ event_str = NULL;
+ }
+
+ free(event_str_);
+ return 0;
+}
+
static int perf_default_core_config(const char *var __maybe_unused,
const char *value __maybe_unused)
{
@@ -454,9 +478,17 @@ static int perf_ui_config(const char *var, const char *value)

static int perf_stat_config(const char *var, const char *value)
{
+ int err = 0;
+
if (!strcmp(var, "stat.big-num"))
perf_stat__set_big_num(perf_config_bool(var, value));

+ if (!strcmp(var, "stat.bpf-counter-events")) {
+ err = perf_stat_config_parse_bpf_counter_event(value);
+ if (err)
+ return err;
+ }
+
/* Add other config variables here. */
return 0;
}
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index 2d2614eeaa20e..592d93bcccd04 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -492,6 +492,8 @@ const char *evsel__hw_names[PERF_COUNT_HW_MAX] = {
"ref-cycles",
};

+bool evsel__use_bpf_counters[PERF_COUNT_HW_MAX] = {false};
+
static const char *__evsel__hw_name(u64 config)
{
if (config < PERF_COUNT_HW_MAX && evsel__hw_names[config])
diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index dd4f56f9cfdf5..32439c5684f7d 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -247,6 +247,7 @@ extern const char *evsel__hw_cache_op[PERF_COUNT_HW_CACHE_OP_MAX][EVSEL__MAX_ALI
extern const char *evsel__hw_cache_result[PERF_COUNT_HW_CACHE_RESULT_MAX][EVSEL__MAX_ALIASES];
extern const char *evsel__hw_names[PERF_COUNT_HW_MAX];
extern const char *evsel__sw_names[PERF_COUNT_SW_MAX];
+extern bool evsel__use_bpf_counters[PERF_COUNT_HW_MAX];
int __evsel__hw_cache_type_op_res_name(u8 type, u8 op, u8 result, char *bf, size_t size);
const char *evsel__name(struct evsel *evsel);

diff --git a/tools/perf/util/target.h b/tools/perf/util/target.h
index 1bce3eb28ef25..4ff56217f2a65 100644
--- a/tools/perf/util/target.h
+++ b/tools/perf/util/target.h
@@ -66,11 +66,6 @@ static inline bool target__has_cpu(struct target *target)
return target->system_wide || target->cpu_list;
}

-static inline bool target__has_bpf(struct target *target)
-{
- return target->bpf_str || target->use_bpf;
-}
-
static inline bool target__none(struct target *target)
{
return !target__has_task(target) && !target__has_cpu(target);
--
2.30.2