sched-pipe.c

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/*
 *
 * sched-pipe.c
 *
 * pipe: Benchmark for pipe()
 *
 * Based on pipe-test-1m.c by Ingo Molnar <[email protected]>
 *  http://people.redhat.com/mingo/cfs-scheduler/tools/pipe-test-1m.c
 * Ported to perf by Hitoshi Mitake <[email protected]>
 *
 */

#include "../perf.h"
#include "../util/util.h"
#include "../util/parse-options.h"
#include "../builtin.h"
#include "bench.h"

#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <sys/wait.h>
#include <linux/unistd.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <sys/time.h>
#include <sys/types.h>

#define LOOPS_DEFAULT 1000000
static int loops = LOOPS_DEFAULT;

static const struct option options[] = {
    OPT_INTEGER('l', "loop", &loops,
            "Specify number of loops"),
    OPT_END()
};

static const char * const bench_sched_pipe_usage[] = {
    "perf bench sched pipe <options>",
    NULL
};

int bench_sched_pipe(int argc, const char **argv,
             const char *prefix __maybe_unused)
{
    int pipe_1[2], pipe_2[2];
    int m = 0, i;
    struct timeval start, stop, diff;
    unsigned long long result_usec = 0;

    /*
     * why does "ret" exist?
     * discarding returned value of read(), write()
     * causes error in building environment for perf
     */
    int __maybe_unused ret, wait_stat;
    pid_t pid, retpid __maybe_unused;

    argc = parse_options(argc, argv, options,
                 bench_sched_pipe_usage, 0);

    BUG_ON(pipe(pipe_1));
    BUG_ON(pipe(pipe_2));

    pid = fork();
    assert(pid >= 0);

    gettimeofday(&start, NULL);

    if (!pid) {
        for (i = 0; i < loops; i++) {
            ret = read(pipe_1[0], &m, sizeof(int));
            ret = write(pipe_2[1], &m, sizeof(int));
        }
    } else {
        for (i = 0; i < loops; i++) {
            ret = write(pipe_1[1], &m, sizeof(int));
            ret = read(pipe_2[0], &m, sizeof(int));
        }
    }

    gettimeofday(&stop, NULL);
    timersub(&stop, &start, &diff);

    if (pid) {
        retpid = waitpid(pid, &wait_stat, 0);
        assert((retpid == pid) && WIFEXITED(wait_stat));
    } else {
        exit(0);
    }

    switch (bench_format) {
    case BENCH_FORMAT_DEFAULT:
        printf("# Executed %d pipe operations between two tasks\n\n",
            loops);

        result_usec = diff.tv_sec * 1000000;
        result_usec += diff.tv_usec;

        printf(" %14s: %lu.%03lu [sec]\n\n", "Total time",
               diff.tv_sec,
               (unsigned long) (diff.tv_usec/1000));

        printf(" %14lf usecs/op\n",
               (double)result_usec / (double)loops);
        printf(" %14d ops/sec\n",
               (int)((double)loops /
                 ((double)result_usec / (double)1000000)));
        break;

    case BENCH_FORMAT_SIMPLE:
        printf("%lu.%03lu\n",
               diff.tv_sec,
               (unsigned long) (diff.tv_usec / 1000));
        break;

    default:
        /* reaching here is something disaster */
        fprintf(stderr, "Unknown format:%d\n", bench_format);
        exit(1);
        break;
    }

    return 0;
}