root/tools/perf/bench/synthesize.c
// 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 <errno.h>
#include <stdio.h>
#include "bench.h"
#include "../util/debug.h"
#include "../util/session.h"
#include "../util/stat.h"
#include "../util/synthetic-events.h"
#include "../util/target.h"
#include "../util/thread_map.h"
#include "../util/tool.h"
#include "../util/util.h"
#include <linux/atomic.h>
#include <linux/err.h>
#include <linux/time64.h>
#include <subcmd/parse-options.h>

static unsigned int min_threads = 1;
static unsigned int max_threads = UINT_MAX;
static unsigned int single_iterations = 10000;
static unsigned int multi_iterations = 10;
static bool run_st;
static bool run_mt;

static const struct option options[] = {
        OPT_BOOLEAN('s', "st", &run_st, "Run single threaded benchmark"),
        OPT_BOOLEAN('t', "mt", &run_mt, "Run multi-threaded benchmark"),
        OPT_UINTEGER('m', "min-threads", &min_threads,
                "Minimum number of threads in multithreaded bench"),
        OPT_UINTEGER('M', "max-threads", &max_threads,
                "Maximum number of threads in multithreaded bench"),
        OPT_UINTEGER('i', "single-iterations", &single_iterations,
                "Number of iterations used to compute single-threaded average"),
        OPT_UINTEGER('I', "multi-iterations", &multi_iterations,
                "Number of iterations used to compute multi-threaded average"),
        OPT_END()
};

static const char *const bench_usage[] = {
        "perf bench internals synthesize <options>",
        NULL
};

static atomic_t event_count;

static int process_synthesized_event(const struct perf_tool *tool __maybe_unused,
                                     union perf_event *event __maybe_unused,
                                     struct perf_sample *sample __maybe_unused,
                                     struct machine *machine __maybe_unused)
{
        atomic_inc(&event_count);
        return 0;
}

static int do_run_single_threaded(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 time_average, time_stddev, event_average, event_stddev;
        int err;
        struct stats time_stats, event_stats;

        init_stats(&time_stats);
        init_stats(&event_stats);

        for (i = 0; i < single_iterations; i++) {
                atomic_set(&event_count, 0);
                gettimeofday(&start, NULL);
                err = __machine__synthesize_threads(&session->machines.host,
                                                NULL,
                                                target, threads,
                                                process_synthesized_event,
                                                true, 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;
                update_stats(&time_stats, runtime_us);
                update_stats(&event_stats, atomic_read(&event_count));
        }

        time_average = avg_stats(&time_stats);
        time_stddev = stddev_stats(&time_stats);
        printf("  Average %ssynthesis took: %.3f usec (+- %.3f usec)\n",
                data_mmap ? "data " : "", time_average, time_stddev);

        event_average = avg_stats(&event_stats);
        event_stddev = stddev_stats(&event_stats);
        printf("  Average num. events: %.3f (+- %.3f)\n",
                event_average, event_stddev);

        printf("  Average time per event %.3f usec\n",
                time_average / event_average);
        return 0;
}

static int run_single_threaded(void)
{
        struct perf_session *session;
        struct target target = {
                .pid = "self",
        };
        struct perf_thread_map *threads;
        struct perf_env host_env;
        int err;

        perf_set_singlethreaded();
        perf_env__init(&host_env);
        session = __perf_session__new(/*data=*/NULL, /*tool=*/NULL,
                                      /*trace_event_repipe=*/false, &host_env);
        if (IS_ERR(session)) {
                pr_err("Session creation failed.\n");
                perf_env__exit(&host_env);
                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;
        }

        puts(
"Computing performance of single threaded perf event synthesis by\n"
"synthesizing events on the perf process itself:");

        err = do_run_single_threaded(session, threads, &target, false);
        if (err)
                goto err_out;

        err = do_run_single_threaded(session, threads, &target, true);

err_out:
        if (threads)
                perf_thread_map__put(threads);

        perf_session__delete(session);
        perf_env__exit(&host_env);
        return err;
}

static int do_run_multi_threaded(struct target *target,
                                unsigned int nr_threads_synthesize)
{
        struct timeval start, end, diff;
        u64 runtime_us;
        unsigned int i;
        double time_average, time_stddev, event_average, event_stddev;
        int err = 0;
        struct stats time_stats, event_stats;
        struct perf_session *session;
        struct perf_env host_env;

        perf_env__init(&host_env);
        init_stats(&time_stats);
        init_stats(&event_stats);
        for (i = 0; i < multi_iterations; i++) {
                session = __perf_session__new(/*data=*/NULL, /*tool=*/NULL,
                                              /*trace_event_repipe=*/false, &host_env);
                if (IS_ERR(session)) {
                        err = PTR_ERR(session);
                        goto err_out;
                }
                atomic_set(&event_count, 0);
                gettimeofday(&start, NULL);
                err = __machine__synthesize_threads(&session->machines.host,
                                                NULL,
                                                target, NULL,
                                                process_synthesized_event,
                                                true, false,
                                                nr_threads_synthesize);
                if (err) {
                        perf_session__delete(session);
                        goto err_out;
                }

                gettimeofday(&end, NULL);
                timersub(&end, &start, &diff);
                runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec;
                update_stats(&time_stats, runtime_us);
                update_stats(&event_stats, atomic_read(&event_count));
                perf_session__delete(session);
        }

        time_average = avg_stats(&time_stats);
        time_stddev = stddev_stats(&time_stats);
        printf("    Average synthesis took: %.3f usec (+- %.3f usec)\n",
                time_average, time_stddev);

        event_average = avg_stats(&event_stats);
        event_stddev = stddev_stats(&event_stats);
        printf("    Average num. events: %.3f (+- %.3f)\n",
                event_average, event_stddev);

        printf("    Average time per event %.3f usec\n",
                time_average / event_average);
err_out:
        perf_env__exit(&host_env);
        return err;
}

static int run_multi_threaded(void)
{
        struct target target = {
                .cpu_list = "0"
        };
        unsigned int nr_threads_synthesize;
        int err;

        if (max_threads == UINT_MAX)
                max_threads = sysconf(_SC_NPROCESSORS_ONLN);

        puts(
"Computing performance of multi threaded perf event synthesis by\n"
"synthesizing events on CPU 0:");

        for (nr_threads_synthesize = min_threads;
             nr_threads_synthesize <= max_threads;
             nr_threads_synthesize++) {
                if (nr_threads_synthesize == 1)
                        perf_set_singlethreaded();
                else
                        perf_set_multithreaded();

                printf("  Number of synthesis threads: %u\n",
                        nr_threads_synthesize);

                err = do_run_multi_threaded(&target, nr_threads_synthesize);
                if (err)
                        return err;
        }
        perf_set_singlethreaded();
        return 0;
}

int bench_synthesize(int argc, const char **argv)
{
        int err = 0;

        argc = parse_options(argc, argv, options, bench_usage, 0);
        if (argc) {
                usage_with_options(bench_usage, options);
                exit(EXIT_FAILURE);
        }

        /*
         * If neither single threaded or multi-threaded are specified, default
         * to running just single threaded.
         */
        if (!run_st && !run_mt)
                run_st = true;

        if (run_st)
                err = run_single_threaded();

        if (!err && run_mt)
                err = run_multi_threaded();

        return err;
}