[PATCH v7 10/12] perf stat: Use affinity for reading

Andi Kleen
2019-11-16T05:52:57Z

From: Andi Kleen <ak@linux.intel.com>

Restructure event reading to use affinity to minimize the number
of IPIs needed.

Before on a large test case with 94 CPUs:

% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
3.16 0.106079 4 22082 read

After:

3.43 0.081295 3 22082 read

Signed-off-by: Andi Kleen <ak@linux.intel.com>

---

v2: Use new iterator macros
v3: Use new iterator macros
v4: Change iterator macros even more
v5: Preserve counter->err in all cases
v6: Rename read_counter -> read_counter_cpu
---
tools/perf/builtin-stat.c | 96 ++++++++++++++++++++++-----------------
tools/perf/util/evsel.h | 1 +
2 files changed, 56 insertions(+), 41 deletions(-)

diff --git a/tools/perf/builtin-stat.c b/tools/perf/builtin-stat.c
index 6cb7d4f0f84c..402e23cc775e 100644
--- a/tools/perf/builtin-stat.c
+++ b/tools/perf/builtin-stat.c
@@ -266,15 +266,10 @@ static int read_single_counter(struct evsel *counter, int cpu,
* Read out the results of a single counter:
* do not aggregate counts across CPUs in system-wide mode
*/
-static int read_counter(struct evsel *counter, struct timespec *rs)
+static int read_counter_cpu(struct evsel *counter, struct timespec *rs, int cpu)
{
int nthreads = perf_thread_map__nr(evsel_list->core.threads);
- int ncpus, cpu, thread;
-
- if (target__has_cpu(&target) && !target__has_per_thread(&target))
- ncpus = perf_evsel__nr_cpus(counter);
- else
- ncpus = 1;
+ int thread;

if (!counter->supported)
return -ENOENT;
@@ -283,40 +278,38 @@ static int read_counter(struct evsel *counter, struct timespec *rs)
nthreads = 1;

for (thread = 0; thread < nthreads; thread++) {
- for (cpu = 0; cpu < ncpus; cpu++) {
- struct perf_counts_values *count;
-
- count = perf_counts(counter->counts, cpu, thread);
-
- /*
- * The leader's group read loads data into its group members
- * (via perf_evsel__read_counter) and sets threir count->loaded.
- */
- if (!perf_counts__is_loaded(counter->counts, cpu, thread) &&
- read_single_counter(counter, cpu, thread, rs)) {
- counter->counts->scaled = -1;
- perf_counts(counter->counts, cpu, thread)->ena = 0;
- perf_counts(counter->counts, cpu, thread)->run = 0;
- return -1;
- }
+ struct perf_counts_values *count;

- perf_counts__set_loaded(counter->counts, cpu, thread, false);
+ count = perf_counts(counter->counts, cpu, thread);

- if (STAT_RECORD) {
- if (perf_evsel__write_stat_event(counter, cpu, thread, count)) {
- pr_err("failed to write stat event\n");
- return -1;
- }
- }
+ /*
+ * The leader's group read loads data into its group members
+ * (via perf_evsel__read_counter) and sets threir count->loaded.
+ */
+ if (!perf_counts__is_loaded(counter->counts, cpu, thread) &&
+ read_single_counter(counter, cpu, thread, rs)) {
+ counter->counts->scaled = -1;
+ perf_counts(counter->counts, cpu, thread)->ena = 0;
+ perf_counts(counter->counts, cpu, thread)->run = 0;
+ return -1;
+ }
+
+ perf_counts__set_loaded(counter->counts, cpu, thread, false);

- if (verbose > 1) {
- fprintf(stat_config.output,
- "%s: %d: %" PRIu64 " %" PRIu64 " %" PRIu64 "\n",
- perf_evsel__name(counter),
- cpu,
- count->val, count->ena, count->run);
+ if (STAT_RECORD) {
+ if (perf_evsel__write_stat_event(counter, cpu, thread, count)) {
+ pr_err("failed to write stat event\n");
+ return -1;
}
}
+
+ if (verbose > 1) {
+ fprintf(stat_config.output,
+ "%s: %d: %" PRIu64 " %" PRIu64 " %" PRIu64 "\n",
+ perf_evsel__name(counter),
+ cpu,
+ count->val, count->ena, count->run);
+ }
}

return 0;
@@ -325,15 +318,36 @@ static int read_counter(struct evsel *counter, struct timespec *rs)
static void read_counters(struct timespec *rs)
{
struct evsel *counter;
- int ret;
+ struct affinity affinity;
+ int i, ncpus, cpu;
+
+ if (affinity__setup(&affinity) < 0)
+ return;
+
+ ncpus = evsel_list->core.all_cpus->nr;
+ if (!target__has_cpu(&target) || target__has_per_thread(&target))
+ ncpus = 1;
+ evlist__for_each_cpu (evsel_list, i, cpu) {
+ if (i >= ncpus)
+ break;
+ affinity__set(&affinity, cpu);
+
+ evlist__for_each_entry(evsel_list, counter) {
+ if (evsel__cpu_iter_skip(counter, cpu))
+ continue;
+ if (!counter->err)
+ counter->err = read_counter_cpu(counter, rs,
+ counter->cpu_iter - 1);
+ }
+ }
+ affinity__cleanup(&affinity);

evlist__for_each_entry(evsel_list, counter) {
- ret = read_counter(counter, rs);
- if (ret)
+ if (counter->err)
pr_debug("failed to read counter %s\n", counter->name);
-
- if (ret == 0 && perf_stat_process_counter(&stat_config, counter))
+ if (counter->err == 0 && perf_stat_process_counter(&stat_config, counter))
pr_warning("failed to process counter %s\n", counter->name);
+ counter->err = 0;
}
}

diff --git a/tools/perf/util/evsel.h b/tools/perf/util/evsel.h
index ca82a93960cd..c8af4bc23f8f 100644
--- a/tools/perf/util/evsel.h
+++ b/tools/perf/util/evsel.h
@@ -86,6 +86,7 @@ struct evsel {
struct list_head config_terms;
struct bpf_object *bpf_obj;
int bpf_fd;
+ int err;
bool auto_merge_stats;
bool merged_stat;
const char * metric_expr;
--
2.23.0