bench.c

#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/wait.h>
#include <assert.h>
#include <time.h>

#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

double
gettime(void)
{
    struct timespec ts;
    if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
        perror("clock_getres");
        exit(EXIT_FAILURE);
    }
    return ts.tv_sec + 1e-9 * ts.tv_nsec;
}

void
bench_forks(int nspawns, char *const *args)
{
    double timer = gettime();
    for (int i = 0; i < nspawns; ++i) {
        pid_t pid = fork();
        if (pid < 0) {
            perror("fork");
            exit(EXIT_FAILURE);
        } else if (pid == 0) {
            execvp(args[0], args);
            perror("execvp");
            exit(127);
        } else {
            int status;
            if (waitpid(pid, &status, 0) < 0) {
                perror("waitpid");
                exit(EXIT_FAILURE);
            }
            if (!WIFEXITED(status)) {
                fprintf(stderr, "child process terminated in an abnormal way\n");
                exit(EXIT_FAILURE);
            }
            if (WEXITSTATUS(status) != 0) {
                fprintf(stderr, "child process exited with non-zero exit code %d\n",
                        WEXITSTATUS(status));
                exit(EXIT_FAILURE);
            }
        }
    }
    timer = gettime() - timer;
    printf("%d spawns in %.2lf seconds: %.2lf forks per second\n", nspawns, timer, nspawns / timer);
}

void
check_lua_call(lua_State *L, int retval)
{
    if (retval == 0) {
        return;
    }
    const char *msg = lua_tostring(L, -1);
    fprintf(stderr, "Lua error: %s\n", msg ? msg : "(error object can't be converted to string)");
    exit(EXIT_FAILURE);
}

void
bench_lua(int ncalls, const char *filename, const char *func, const char *arg)
{
    lua_State *L = luaL_newstate();
    assert(L); // L: -
    luaL_openlibs(L); // L: -
    check_lua_call(L, luaL_dofile(L, filename)); // L: -

#if LUA_VERSION_NUM >= 502
    lua_pushglobaltable(L);
#else
    lua_pushvalue(L, LUA_GLOBALSINDEX);
#endif
    // L: _G

    double timer = gettime();

    lua_getfield(L, -1, func); // L: _G func
    int ref = luaL_ref(L, LUA_REGISTRYINDEX); // L: _G
    lua_pop(L, 1); // L: -

    for (int i = 0; i < ncalls; ++i) {
        lua_rawgeti(L, LUA_REGISTRYINDEX, ref); // L: func
        lua_pushstring(L, arg); // L: func arg
        check_lua_call(L, lua_pcall(L, 1, 0, 0)); // L: -
    }

    timer = gettime() - timer;
    printf("%d calls in %.2lf seconds: %.2lf calls per second\n", ncalls, timer, ncalls / timer);

    lua_close(L);
}

int
main()
{
    bench_forks(1000, (char *const[]) {"./my_true", NULL});
    bench_lua(1000, "./file.lua", "my_func", "hello");
}