[PATCH v2 1/5] perf bench: add event synthesis benchmark

Ian Rogers
2020-04-02T15:44:11Z

Event synthesis may occur at the start or end (tail) of a perf command.
In system-wide mode it can scan every process in /proc, which may add
seconds of latency before event recording. Add a new benchmark that
times how long event synthesis takes with and without data synthesis.

An example execution looks like:
$ perf bench internals synthesize
# Running 'internals/synthesize' benchmark:
Average synthesis took: 168.253800 usec
Average data synthesis took: 208.104700 usec

Signed-off-by: Ian Rogers <irogers@google.com>
---
tools/perf/Documentation/perf-bench.txt | 8 ++
tools/perf/bench/Build | 2 +-
tools/perf/bench/bench.h | 2 +-
tools/perf/bench/synthesize.c | 101 ++++++++++++++++++++++++
tools/perf/builtin-bench.c | 6 ++
5 files changed, 117 insertions(+), 2 deletions(-)
create mode 100644 tools/perf/bench/synthesize.c

diff --git a/tools/perf/Documentation/perf-bench.txt b/tools/perf/Documentation/perf-bench.txt
index 0921a3c67381..bad16512c48d 100644
--- a/tools/perf/Documentation/perf-bench.txt
+++ b/tools/perf/Documentation/perf-bench.txt
@@ -61,6 +61,9 @@ SUBSYSTEM
'epoll'::
Eventpoll (epoll) stressing benchmarks.

+'internals'::
+ Benchmark internal perf functionality.
+
'all'::
All benchmark subsystems.

@@ -214,6 +217,11 @@ Suite for evaluating concurrent epoll_wait calls.
*ctl*::
Suite for evaluating multiple epoll_ctl calls.

+SUITES FOR 'internals'
+~~~~~~~~~~~~~~~~~~~~~~
+*synthesize*::
+Suite for evaluating perf's event synthesis performance.
+
SEE ALSO
--------
linkperf:perf[1]
diff --git a/tools/perf/bench/Build b/tools/perf/bench/Build
index e4e321b6f883..042827385c87 100644
--- a/tools/perf/bench/Build
+++ b/tools/perf/bench/Build
@@ -6,9 +6,9 @@ perf-y += futex-wake.o
perf-y += futex-wake-parallel.o
perf-y += futex-requeue.o
perf-y += futex-lock-pi.o
-
perf-y += epoll-wait.o
perf-y += epoll-ctl.o
+perf-y += synthesize.o

perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-lib.o
perf-$(CONFIG_X86_64) += mem-memcpy-x86-64-asm.o
diff --git a/tools/perf/bench/bench.h b/tools/perf/bench/bench.h
index 4aa6de1aa67d..4d669c803237 100644
--- a/tools/perf/bench/bench.h
+++ b/tools/perf/bench/bench.h
@@ -41,9 +41,9 @@ int bench_futex_wake_parallel(int argc, const char **argv);
int bench_futex_requeue(int argc, const char **argv);
/* pi futexes */
int bench_futex_lock_pi(int argc, const char **argv);
-
int bench_epoll_wait(int argc, const char **argv);
int bench_epoll_ctl(int argc, const char **argv);
+int bench_synthesize(int argc, const char **argv);

#define BENCH_FORMAT_DEFAULT_STR "default"
#define BENCH_FORMAT_DEFAULT 0
diff --git a/tools/perf/bench/synthesize.c b/tools/perf/bench/synthesize.c
new file mode 100644
index 000000000000..6291257bc9c9
--- /dev/null
+++ b/tools/perf/bench/synthesize.c
@@ -0,0 +1,101 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Benchmark synthesis of perf events such as at the start of a 'perf
+ * record'. Synthesis is done on the current process and the 'dummy' event
+ * handlers are invoked that support dump_trace but otherwise do nothing.
+ *
+ * Copyright 2019 Google LLC.
+ */
+#include <stdio.h>
+#include "bench.h"
+#include "../util/debug.h"
+#include "../util/session.h"
+#include "../util/synthetic-events.h"
+#include "../util/target.h"
+#include "../util/thread_map.h"
+#include "../util/tool.h"
+#include <linux/err.h>
+#include <linux/time64.h>
+#include <subcmd/parse-options.h>
+
+static unsigned int iterations = 10000;
+
+static const struct option options[] = {
+ OPT_UINTEGER('i', "iterations", &iterations,
+ "Number of iterations used to compute average"),
+ OPT_END()
+};
+
+static const char *const usage[] = {
+ "perf bench internals synthesize <options>",
+ NULL
+};
+
+
+static int do_synthesize(struct perf_session *session,
+ struct perf_thread_map *threads,
+ struct target *target, bool data_mmap)
+{
+ const unsigned int nr_threads_synthesize = 1;
+ struct timeval start, end, diff;
+ u64 runtime_us;
+ unsigned int i;
+ double average;
+ int err;
+
+ gettimeofday(&start, NULL);
+ for (i = 0; i < iterations; i++) {
+ err = machine__synthesize_threads(&session->machines.host,
+ target, threads, data_mmap,
+ nr_threads_synthesize);
+ if (err)
+ return err;
+ }
+
+ gettimeofday(&end, NULL);
+ timersub(&end, &start, &diff);
+ runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
+ average = (double)runtime_us/(double)iterations;
+ printf("Average %ssynthesis took: %f usec\n",
+ data_mmap ? "data " : "", average);
+ return 0;
+}
+
+int bench_synthesize(int argc, const char **argv)
+{
+ struct perf_tool tool;
+ struct perf_session *session;
+ struct target target = {
+ .pid = "self",
+ };
+ struct perf_thread_map *threads;
+ int err;
+
+ argc = parse_options(argc, argv, options, usage, 0);
+
+ session = perf_session__new(NULL, false, NULL);
+ if (IS_ERR(session)) {
+ pr_err("Session creation failed.\n");
+ return PTR_ERR(session);
+ }
+ threads = thread_map__new_by_pid(getpid());
+ if (!threads) {
+ pr_err("Thread map creation failed.\n");
+ err = -ENOMEM;
+ goto err_out;
+ }
+ perf_tool__fill_defaults(&tool);
+
+ err = do_synthesize(session, threads, &target, false);
+ if (err)
+ goto err_out;
+
+ err = do_synthesize(session, threads, &target, true);
+
+err_out:
+ if (threads)
+ perf_thread_map__put(threads);
+
+ perf_session__delete(session);
+ return err;
+}
diff --git a/tools/perf/builtin-bench.c b/tools/perf/builtin-bench.c
index c06fe21c8613..11c79a8d85d6 100644
--- a/tools/perf/builtin-bench.c
+++ b/tools/perf/builtin-bench.c
@@ -76,6 +76,11 @@ static struct bench epoll_benchmarks[] = {
};
#endif // HAVE_EVENTFD

+static struct bench internals_benchmarks[] = {
+ { "synthesize", "Benchmark perf event synthesis", bench_synthesize },
+ { NULL, NULL, NULL }
+};
+
struct collection {
const char *name;
const char *summary;
@@ -92,6 +97,7 @@ static struct collection collections[] = {
#ifdef HAVE_EVENTFD
{"epoll", "Epoll stressing benchmarks", epoll_benchmarks },
#endif
+ { "internals", "Perf-internals benchmarks", internals_benchmarks },
{ "all", "All benchmarks", NULL },
{ NULL, NULL, NULL }
};
--
2.26.0.rc2.310.g2932bb562d-goog